Bosch AquaStar 125B LPS Manual

WARNING: Improper installation,
adjustment, alteration, service or maintenance can cause
injury or property damage. Refer to this manual. For
assistance or additional information consult a ualified
installer, service agency or the gas supplier. Upon
completion of the installation, these instructions should
be handed to the user of the appliance for future
reference.
In the Commonwealth of Massachusetts this product
must be installed by a licensed plumber or gas fitter.
FEATURING: Automatic Variable Power Modulating Gas
Valve wit T ermostatic Control
Warning: If you do not follow t ese instructions exactly, a
fire or explosion may result causing property damage,
personal injury or loss of life.
INSTALLATION AND OPERATING INSTRUCTIONS FOR AUTOMATIC
INSTANTANEOUS TYPE WATER HEATERS FOR USE WITH NATURAL AND
LIQUEFIED PETROLEUM GAS
WARNING
If the information in this manual is not followed exactly, a
fire or explosion may result causing property damage,
personal injury or death.
FOR YOUR SAFETY
Do not store or use gasoline or other flammable,
combustible or corrosive vapors and li uids in the vicinity
of this or any other appliance.
WHAT TO DO IF YOU SMELL GAS
-Do not try to light any appliance.
-Do not touch any electrical switch; do not use any
phone in your building.
-Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions.
-If you cannot reach your gas supplier, call the fire
department.
- Installation and service must be performed by a
ualified installer, service agency or the gas supplier.
Specifications................................................................. Page 2
Rules for safe operation ............................................... Page 4
Locating t e Heater ......................................................Page 4
Combustion Air Requirements .................................... Page 5
Mounting t e Heater ..................................................... Page 6
Venting t e Heater ........................................................ Page 7
Gas Connections ....................................................... Page 10
Water Connections .................................................... Page 11
Safety before lig ting t e pilot ................................ Page 12
Lig ting instructions ................................................... Page 12
Information on water temperature ........................... Page 13
Maintenance & Service ............................................. Page 13
Trouble S ooting ......................................................... Page 14
Diagram of AquaStar .................................................. Page 17
Components and Parts List ...................................... Page 19
Warranty ....................................................................... Page 21
TABLE OF CONTENTS
6 720 606 518 US (04.11) AL
MODEL 125B LPS and 125B NGS (Thermostatically Modulated)
Suitable for heating potable water only
Not approved for space heating purposes
Intended for domestic hot water with preheated inlet water as with solar hot water.

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This well engineered, gas water heater has been specially
designed to operate with incoming pre-heated water:
It operates on t e principle of eating water instantaneously
“on demand”. W en a ot water faucet is opened, cold water
flows t roug t e coils of t e eat exc anger in t e Aquastar.
T is same flow opens t e gas valve, and t e burners are
ignited by t e pilot flame. T e eat exc anger coils absorb
t e eat generated by t e burners and transfer eat to t e
water. W en t e ot water faucet is s ut off, t e gas valve
automatically closes and t e burners turn off. Your ot water
faucet is an ignition key to turn on t e water eater, giving
you control over your ot water energy use. Eac time you
turn off your ot water faucet, you also s ut off t e water
eater. On t e Aquastar “S” model, if t e incoming water is
colder t an t e t ermostat setting of t e eater, t e burners
will ignite to eat t e water in order to boost it and maintain
it at t e temperature setting. If t e incoming water as been
pre- eated, (ie) solar, and t is water temperature is warm
t en t e t e burners will modulate down accordingly, or
s ut down completely if t e temperature is as ot or otter
t an t e eater t ermostat setting. T e Aquastar 125 BS is
t e perfect backup to a solar ot water system.
FEATURES
- Hig Quality Materials for Long Working Life.
- Copper eating coils for endless supply of ot water.
- Burner output proportional to ot water flow demand for
maximum energy efficiency.
- Automatic T ermostatic Control for steady ot water
temperature
- Input BTU’s modulate to zero to prevent over eating of
water from pre- eat source
- Safety t ermocouple at pilot burner.
- Automatic over eating protection s ut-off sensor.
- Stainless steel burners wit stabilized blue flame.
- Built-in corrosion resistant draft inducer.
- Compact space saver: mounts on a wall wit two ooks.
- Easily removable one-piece cover.
- Easy one person installation.
- Adjustable water flow restrictor to ensure t at water flow
demand will not exceed t e eating capacity of t e eater.
- Easy pilot flame lig ting wit pus button piezo ignition.
BOSCH is constantly improving our products, therefore
specifications are subject to change without prior notice.
A uaStar 125B LPS and 125B NGS Specifications
Gas Input max.: 117,000 Btu/ r
min.: 23,400 Btu/ r
Water Connection 1/2” T read fitting NPT
H x W x D 29 3/4” x 18 1/4” x 8 3/4"
Vent 5”
Gas Connection 1/2” NPT t read
Min. Water Pressure 18 Psi at 4 GPM
Max. Water Pressure 150 Psi
S ipping Weig t 44 LB
Net Weig t 42 LB
1.8 GPM at 90° rise
3.7 GPM at 45° rise
Min. Water Flow 1/2 gal/min
LP GAS Supply Pressure
(before Aquastar regulator) min.: 11” W.C.
max.: 14” W.C.*
Required LP GAS Pressure at inlet
tap w ile Aquastar is operating: 10.5” W.C.
LP GAS Burner Manifold pressure w ile Aquastar
is operating at maximum input: 9.0” W.C.
Natural Gas Supply Pressure
(before Aquastar regulator) min.: 7” W.C.
max.: 14” W.C.*
Required Natural Gas Pressure at inlet tap
w ile Aquastar is operating: 5.7” W.C.
Natural Gas Burner Manifold pressure w ile Aquastar is
operating at maximum input: 4.2” W.C.
* Inlet gas pressure before Aquastar regulator must not
exceed t is value. Pressure may need to be adjusted for
ig altitudes, see page 11.
UNPACKING THE AQUASTAR HEATER
T is eater is packed securely. T e box includes two water
connection fittings, a gas pressure regulator, a pressure relief
valve, an incandescent particle tray, two ooks for anging
t e eater, t is manual, a warranty statement and a warranty
registration card. Do not lose this manual, as there is a
charge for replacement. Please complete and return t e
enclosed warranty registration card.

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D861_059
MINIMUM INSTALLATION CLEARANCES FROM COMBUSTIBLE AND NON
COMBUSTIBLE MATERIALS FOR ALCOVE OR CLOSET INSTALLATIONS
FRONT VIEW SIDE VIEW
AQUASTAR MODEL 125BS
MODEL 125BS
TOP (A) 12 "
FRONT (B) 4 "
BACK 0 "
SIDES 4 "
FLOOR (C) 12 "
VENT DIAMETER 5 "

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PROPER LOCATION FOR INSTALLING YOUR
HEATER
Carefully select t e location of your new eater. For your
safety and for proper eater operation, you must provide an
abundant supply of combustion air and a proper venting
installation.
T e eater may still operate even w en improperly vented.
It will, owever, be less efficient and could eventually damage
t e eater. It could even result in uman sickness or deat
due to oxygen deprivation and carbon monoxide poisoning.
Follow t e guidelines below:
1. Place your eater as close to a vent or c imney as
possible.
2. National building codes require t at you do not install
t is appliance in bat rooms, bedrooms, unvented closet or
any occupied rooms normally kept closed.
3. Simultaneous operation of ot er appliances suc as
ex aust fans, ventilation systems, clot es dryers, fireplaces
or wood stoves could create a vacuum effect in your ome
w ic could cause dangerous combustion by-products to
spill back into your ome rat er t an venting to t e outside
t roug t e flue. Confirm t at your Aquastar is venting
properly w en all t ese ot er appliances are running. See
section on venting.
Do not obstruct the flow of combustion and ventilation
air to the appliance. If installed near a clot es dryer it is
very important t at t e dryer be properly vented. Failure to
properly vent a dryer could result in a gradual accumulation
of lint on t e water eater fin coils and burners, leading to a
dangerous condition of vent blockage and poor unsafe
combustion.
4. Your ot water lines s ould be kept s ort to save energy.
It is always best to ave ot water lines insulated.
WARNING: T e water in t is water eater is cold
and always remains cold except for t e times t at ot water
is being used. DO NOT INSTALL IN AN AREA WHERE IT
COULD FREEZE.
This heater is neither designed for not approved for
outside installation. Drain t e eater entirely if freezing
temperatures are anticipated in t e area w ere eater is
installed by disconnecting bot t e inlet and outletelbow
connections at t e rear of eater. Additionally remove t e
drain plug under t e water valve. See Fig 0.
GENERAL RULES TO FOLLOW
FOR SAFE OPERATION
1. You s ould follow t ese instructions w en you install your
eater. In t e United States: T e installation must conform
wit local codes or, in t e absence of local codes, t e
National Fuel Gas Code ANSI Z223.1/NFPA 54.
In Canada: T e Installation s ould conform wit CGA
B149.(1,2) INSTALLATION CODES and/or local installation
codes.
2. Carefully plan w ere you install t e eater. Correct
combustion air supply and flue pipe installation are very
important. If not installed correctly, fatal accidents can be
caused by lack of air, carbon monoxide poisoning or fire.
3. T e place w ere you install t e eater must ave enoug
ventilation. T e National Fire Codes do not allow gas fired
water eater installation in bat rooms, bedrooms or any
occupied rooms normally kept closed. See t e section below
on locating t e eater.
4. You must vent your eater. See section on VENTING,
Page 6.
5. T e appliance must be disconnected from t e gas supply
piping system during any pressure testing at pressures in
excess of 1/2 Psig (3.5 kPa).
T e appliance must be isolated from t e gas supply piping
system by closing its individual manual s utoff valve during
any pressure testing of t e gas supply piping system at test
pressures equal to or more t an 1/2 Psig (3.5Kpa). T e
appliance and its gas connection must be leak tested before
placing t e appliance in operation.
6. Keep water eater area clear and free from combustibles
and flammable liquids. Do not locate t e eater over any
material w ic mig t burn.
7. Correct gas pressure is critical for t e optimum
operation of t is eater (see specifications on page 2). Gas
piping must be sized to provide t e required pressure at t e
maximum output of t e eater, w ile all t e ot er gas
appliances are in operation. C eck wit your local gas
supplier, and see t e section on connecting t e gas supply.
8. S ould over eating occur or t e gas supply fail to s ut
off, turn off t e gas supply at t e manual gas s ut off valve
on t e gas line.
9. Do not use t is appliance if any part as been underwater.
Immediately call a qualified service tec nician to inspect
t e appliance and to replace any part of t e control system
and any gas control w ic as been underwater.
This product is not approved for manufactured homes
(mobile home), recreational vehicles (RV) or boats.
Reference ANSI Z21.10.3.
This product is neither designed or approved for outside
installations.
Fig. 0 - Water heater drain plug

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WARNING: Flammable materials, gasoline,
pressurized containers, or any other items or articles
that are potentially fire hazards must NOT be placed on
or adjacent to the heater. The appliance area must be
kept free of all combustible materials, gasoline and other
flammable vapors and li uids.
COMBUSTION AIR REQUIREMENTS
T e AquaStar water eater olds cold water in its copper
eat exc anger and brass water valve w en not in use.
Because of t is, any cold air t at comes in t roug t e
unit’s vent pipe is capable of freezing t ese components.
T is Installation Manual specifies t e minimum vertical vent
pipe and t e amount of combustion air required for t is unit.
W en all requirements are followed, t e unit will operate
properly and safely. However, t ere may still be a risk of
freezing due to negative draft if all t e combustion appliances
in t e area are not being supplied wit a sufficient amount
of make-up air. A wood stove or furnace can rob t e make-
up air in t e AquaStar’s vent pipe, leaving t e cold infiltrating
air capable of freezing t e cold water in t e AquaStar eat
exc anger. More make up air is t e solution. Follow t e
instructions on venting and c ecking adequacy of make up
air. A HVAC specialist s ould be used to design solutions
for providing more make-up air if necessary.
Observe t e following instructions concerning combustion
air.
Appliances located in unconfined spaces:
a) An unconfined space is one w ose volume is greater
t an 50 cubic feet per 1000 Btu per our of t e combined
rating of all appliances installed in t e space. T at would
be 5850 cubic feet for t e AquaStar 125B “S” alone.
b) In unconfined spaces in buildings of conventional frame,
masonry, or metal construction, infiltration is normally
adequate to provide air for combustion, ventilation, and
dilution of flue gasses.
Appliances located in confined spaces:
T e confined space must be provided wit two permanent
openings, one commencing wit in 12 inc es of t e top and
one commencing wit in 12 inc es of t e bottom of t e
enclosure. Eac opening must ave a minimum free area of
one square inc per:
- 1000 Btu/ r if all air is taken from inside t e building.
- 2000 Btu/ r if all air is taken from t e outside by orizontal
ducts.
- 4000 Btu/ r if all air is taken from t e outside by direct
openings or vertical ducts.
Or t e confined space must be provided wit one permanent
opening or duct t at is wit in 12 inc es of t e ceiling of t e
enclosure. T is opening must ave a minimum free area of
one square inc per:
- 3000 Btu/ r if all air is taken from t e outside by a direct
opening or vertical duct.
Louvers, grills and screens ave a blocking effect. If t e
effective free area is not known, increase t e sizes of your
openings by 75% if your louvers are wood and by 30% if
your louvers are metal. Refer to t e National Fuel Gas Code
for complete information. In buildings of tig t construction
all air s ould be taken from outside.
CLEARANCES
T e Aquastar 125 B “S” is design certified for installation
on a combustible wall and for installation in an alcove or
closet wit t e minimum clearances to combustible and non
-combustible construction listed below
A. Top 12 inc es (306 mm)
B. Front 4 inc es (102 mm)
C. Back 0 inc es
D. Sides 4 inc es (102mm)
E. Bottom 12 inc es (306 mm)
Clearance from vent is dependent upon t e clearance rating
of t e venting material used. For example, type B-a vent is
approved for 1 inc clearance.
Note: Typically, t e minimum clearance to combustible
materials s ould not be less t an 6” for single wall flue
pipe. Note t at t is clearance can be reduced if combustible
materials are protected as per table VI of t e National Fuel
Gas Code or if Type B gas vent is used.
125BS Air Vents
(5 ½ X 5 ½ in. each)
Air Vents
(10 ¾ X 10 ¾ in. each) 125BS

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Fig. 1 - Mounting the Heater
Fig. 2 - Incandescent Particle Tray Illustration
T e incandescent particle tray (s ipped loose in t e carton
wit t e water eater) must be attac ed at t e bottom of
t e water eater front cover at t e time of installation. Use
t e screws provided. See figure 2
SUPPORT BOARD
WALL STUDS
1” X 4”
SPACE BOARD
13 ¼”
SCREWS
INCANDESCENT PARTICLE TRAY
MOUNTI NG IN STALLATION
T e Aquastar 125 B “S” is design certified for mounting on
a wall.
Secure t e two L s aped ooks provided wit t e eater to
a wall surface. Place t em 13 ¼ inc es apart as s own in
Fig 1. Do not install t is appliance on a carpeted wall or
over floor covering w ic is combustible, suc as carpet.
T e eater must be mounted on a wall using appropriate
anc oring materials. If wall is a stud wall s eat ed wit
plasterboard, it is recommended that support board(s),
either 1x4’s or 1/2" (minimum) plywood first be attached
across a pair of studs and then the heater should be
attached to the support boards. See Fig 1.
Expansion and contraction of piping due to c anging water
temperature in t e pipes imparts movement to t e eater
w ic , if mounted directly to a brittle, friable board, suc as
plasterboard, can cause failure of mounting.
In eart quake-prone zones, CEC recommends t at installers
use a large was er and lag screw t roug t e existing oles
used to ang t e eater to affix t e upper t ird of t e eater
to t e mounting board. To affix t e lower t ird of t e eater,
CEC recommends t at two new oles be drilled in t e
eater’s frame, eac one 16 inc es below t e top two oles,
and t at was ers and lag screws be used to secure t e
lower portion of t e eater to a spacing board.
Before installing the unit, be certain you have the correct
heater for your type of Gas – Propane or Natural Gas.
Identification labels are found on the shipping box, and on
the rating plate which is located on the right side panel of
t e cover. Also, eac burner orifice is stamped wit a number
(79 for LPG and 120 for Natural Gas).

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VENTING
Vent pipe connection. WARNING: Do not reduce the vent pipe size. See Fig. 3 for high altitude installations
T e eater must be vented to t e outside following all local ordinances and specifications for installing a gas appliance
vent or c imney. T e eater must be located as close as practicable to a vertically rising c imney or vent t at as a listed
vent cap at its termination point. T e venting system must be designed and constructed so as to develop a positive flow
adequate to remove flue gasses to t e outdoors.
Consult the National Fuel Gas Code if the vent will have elbows or share venting with another natural draft appliance.
The heater should never be common vented with a mechanically vented appliance. Single wall vent pipe is not
recommended, if used consult the National Fuel Gas Code.
Horizontally venting to a sidewall vent terminator or a vertically constructed vent stack along an outside wall of a building
is not permissible. A Powervent (Model AQ-1), wit a proof-of-draft safety interlock device, is required and is available in
order to sidewall vent. Contact your dealer. In the Commonwealth of Massachusetts: Powervented applications must
utilize proof-of-draft safety interlock device.
VERTICAL GAS VENT: A 5 inc diameter gas vent constructed of double wall Type B gas vent is recommended. 6 inc is
required in elevations greater t an 2000 feet, see Fig. 3. Any gas vent section t at is greater t an 45 degrees from t e
vertical is considered orizontal. Horizontal sections must slope upwards at least ¼ inc for every foot of its orizontal
lengt and be properly supported. Keep t e orizontal section s ort and avoid too many elbows. T e minimum vertical gas
vent eig t allowed is 6 feet; orizontal vent connectors and elbows are not to be considered in t e total gas vent eig t.
All gas vent sections must be secured to eac ot er wit s eet metal screws and be properly supported.
T e gas vent constructed of double wall Type B gas vent must terminate above t e roof surface wit a listed vent cap at
a eig t t at’s in accordance wit Figure A or B and t eir table, provided t ey are at least 8 feet (2.4 m) from a vertical wall
or similar obstruction. All ot er gas vents t at are not able to terminate wit in t e minimum specified eig t allowed must
terminate not less t an 2 feet (0.6 m) above t e ig est point w ere it’s passed t roug t e roof and at least 2 feet (0.6
m) ig er t an any vertical wall or similar obstruction wit in 10 feet (3.1 m).
LISTED VENT CAP
LISTED VENT CAP
LISTED GAS VENT
LOWEST DISCHARGE OPENING
H (minimum) eig t
from roof to lowest
disc arge opening
Figure A Figure B
ROOF PITCH
IS X/12
12
X
Roof pitch H (minimum) feet meters
Flat to 6/12 1.0 0.30
6/12 to 7/12 1.25 0.38
Over 7/12 to 8/12 1.5 0.46
Over 8/12 to 9/12 2.0 0.61
Over 9/12 to 10/12 2.5 0.76
Over 10/12 to 11/12 3.25 0.99
Over 11/12 to 12/12 4.0 1.22
Over 12/12 to 14/12 5.0 1.52
Over 14/12 to 16/12 6.0 1.83
Over 16/12 to 18/12 7.0 2.13
Over 18/12 to 20/12 7.5 2.27
Over 20/12 to 21/12 8.0 2.44
GAS VENT TERMINATIONS FOR LISTED VENT CAPS

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MASONRY CHIMNEY: Masonry c imneys s all be built and installed in accordance wit NFPS 211 or local codes. A
minimum 5” diameter gas vent pipe (metal double wall Type B), or an approved clay flue liner or a listed c imney lining
system must be used w en venting into a naturally drafting, internal masonry c imney. 6 inc is required in elevations
greater t an 2000 feet, see Fig. 3. Local codes may require t e use of bot gas vent and an approved lining system w en
venting into a masonry c imney. T e Commonwealt of Massac usetts requires t e use of a listed liner. Lining systems
include approved clay flue lining, a listed c imney lining system or ot er approved material t at will resist corrosion,
erosion, softening, or cracking from ex aust flue gases at temperatures up to 1800 degrees F. T e lining system must be
listed for use wit naturally drafting, draft ood equipped gas appliances. Follow local codes and refer to NFGC 54 and
NFPA 58.
When connecting the water heater to a masonry chimney the following connector guidelines must be followed for
safe and proper operation: An approved gas vent connector must be attac ed to t e top of t e water eater and rise
vertically at least 12” before entering into an approved gas vent connector elbow. Any gas vent section t at is greater t an
45 degrees from t e vertical is considered orizontal. If a orizontal vent connector is to be used to connect t e vertical
gas vent connector on t e top of t e water eater to t e masonry c imney, t at approved orizontal gas vent connector
must be kept as s ort as possible and must be sloped upwards at least ¼” per foot of its lengt . T is connector must be
supported t roug out its orizontal lengt . T is orizontal gas vent connection may be no greater t an 75% of t e total
vertical gas flue vent wit in t e c imney. Also, an approved t imble or collar must be used w en penetrating a masonry
c imney.
A) Existing INTERIOR Masonry Chimney
T e metal gas vent pipe s ould be permanently mounted inside t e masonry c imney. Double wall Type B gas vent is
recommended. T e masonry c imney may ave to be tile or metal lined before t e insertion of t e gas vent pipe; c eck
local codes for clarification. T e lining material must be listed for use only wit naturally drafting, draft ood equipped gas
appliances. Follow manufactures instructions for installation of listed lining material. You may not vent any ot er fuel
burning appliances into any free space remaining in t e c imney. T e minimum vertical gas vent lengt wit in t e masonry
c imney s ould be no less t an 5 ft (1.5 m); t e vent terminator s ould extend at least 3 feet (0.9 m) above w ere t e
c imney meets t e roofline and at least 2 feet (0.6 m) ig er t an any vertical wall or similar obstruction wit in 10 feet (3.1
m). T e top of t e gas vent s ould ave an approved vent terminator. See Figure C.
B) Tile Lined INTERIOR Masonry Chimney
T e masonry c imney must ave an approved liner, ceramic tile, clay or metal. T e masonry c imney must be able to
accommodate t e spent fuel gasses; consult a HVAC engineer for c imney capacity. A common venting like-fuel appliance
into t is lined masonry c imney is permissible. T e c imney’s diameter must be large enoug to adequately draft t e spent
fuel gasses. See NFPA 54 for guidelines. A HVAC engineer will be required to spec a c imney system. T e minimum
vertical c imney lengt s ould be no less t an 5 ft (1.5 m); t e termination point s ould extend at least 3 feet (0.9 m)
above w ere t e c imney meets t e roofline and at least 2 feet (0.6 m) ig er t an any vertical wall or similar obstruction
wit in 10 feet (3.1 m). See Figure C.
C) EXTERIOR masonry Chimney
Refer to t e National Fuel Gas Code and consult a local HVAC professional.
MASONRY CHIMNEYS
GAS
VENT
LISTED VENT CAP
VENT CONNECTOR
ESTABLISH A ONE
FOOT RISE BEFORE
ANY ELBOWS
Figure C

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Fig. 3 – Vent Adaptor for High Altitude Installations
5” X 6” ADAPTOR
USED ON HIGH ALTITUDE
To check the draft:
Close all doors and windows to t e outside.
Turn on all appliances t at force air out of t e building.
T ese include all ex aust/ventilation fans, furnaces, clot es
dryers, wood burning stoves, etc.
Open all doors between t e AquaStar and t ese ot er
appliances.
Run t e unit for at least 10 minutes. T en old an ordinary
mirror at t e side above t e front s ell. Any flue gases
backdrafting will cause t e mirror to fog. T is is a serious
ealt azard and must be corrected. Poor venting can result
in soot building up inside t e eater, over eating of t e eater
and freezing of t e eat exc anger in a freezing environment.
T e mirror will remain clear wit a properly functioning draft.
WARNING
Note: T e burners of an instantaneous “on demand” water
eater suc as t e AquaStar are only on at t e time t at
ot water is actually being used, t e vent pipe is t erefore
cold except for t e s ort durations w en ot water is being
used, it is t erefore very important t at t e venting and air
supply be adequate to provide a good positive draft as soon
as t e burners turn on. See venting guide on back page.
T e AquaStar 125B”S” instantaneous water eaters ave
built-in draft diverters and are designed for indoor installation
only. T e draft diverter outlet must be connected to an
unobstructed vent of t e same size, or larger.
In Canada, CAN/CGA-B149 Installation Code for detailed
requirements
In U.S.A., ANSI Z223.1 - NFPA 54, National Fuel Gas
Code for detailed requirements.
T e vent connection for t e Aquastar 125BS is 5 inc es.
However, for installations at ig altitude (over 2000 feet
above sea level) a six inc vent is required. A 5” by 6” vent
adaptor must be affixed to t e flue collar of t e Aquastar
wit at least two screws. See Fig. 3.
WARNING: Failure TO INCREASE THE VENT
SIZE TO SIX INCHES AND/or assure t at t e manifold
pressure is set to proper value listed for applications at ig
altitudes will cause unsafe venting, asp yxiation, and will
void CSA Certification.

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GAS CONNECTIONS and Gas Regulator
NOTE: The A uastar 125 B”S” is supplied with a gas pressure regulator that must be installed on the heater before
attaching the gas supply line. See figure 5. Failure to install the gas regulator as shown in figure 5 will be a violation
of CSA certification of the unit. The regulator supplied with the heater is preset for the gas shown on the rating
plate to the correct pressure. It is an appliance level regulator designed for (low inlet) pressure (less than 1/2 Psig
or 15” W.C.) DO NOT connect to an unregulated or high pressure propane line or to a high pressure commercial
natural gas line.
FOR NATURAL GAS
Maximum Capacity of pipe in Cubic Feet of Gas per Hour
for Gas Pressure of 0.5 Psig or less and a Pressure drop of
0.3 in Water Column.
(Based on a 0.60 Specific Gravity Gas) Btu numbers given
in t ousands.
Follow boxed numbers for piping just one Aquastar 125BS
(example: 3/4” B.I. Natural Gas pipe for 30 ft. will andle
152,000 btu’s). For multiple appliances combine t e total
btu input load and t en refer to applicable c art below.
FOR LP GAS
Maximum Capacity of Pipe in T ousands of
BTU per Hour of Undiluted Petroleum Gases
(at 11 inc es Water Column Inlet Pressure)
(Based on a Pressure Drop of 0.5 Inc Wa-
ter Column).
Maximum Capacity of Semi-Rigid
Tubing in T ousands of BTU per Hour of
Undiluted Liquified Petroleum Gases (at 11
inc es Water Column Inlet Pressure)
(Based on a Pressure Drop of 0.5 Inc Water
Column)
* Source National Fuel Gas Code NFPA 54, ANSI Z223.1 - No
Additional Allowance is necessary for an ordinary number of fittings
GAS LINE SIZING
Nominal
Iron Length of Black Iron Pipe, Feet
Pipe Internal
Size, Diameter
inches inches 10 20 30 40 50 60 70 80 90 100 125 150 175 200
1/4 0.364 32 22 18 15 14 12 11 11 10 9 8 8 7 6
3/8 0.493 72 49 40 34 30 27 25 23 22 21 18 17 15 14
1/2 0.622 132 92 73 63 56 50 46 43 40 38 34 31 28 26
3/4 0.824 278 190 152 130 115 105 96 90 84 79 72 64 59 55
1 1.049 520 350 285 245 215 195 180 170 160 150 130 120 110 100
1 1/4 1.380 1050 730 590 500 440 400 370 350 320 305 275 250 225 210
1 1/2 1.610 1600 1100 890 760 670 610 560 530 490 460 410 380 350 320
2 2.067 3050 2100 1650 1450 1270 1150 1050 990 930 870 780 710 650 610
2 1/2 2.469 4800 3300 2700 2300 2000 1850 1700 1600 1500 1400 1250 1130 1050 980
3 3.068 8500 5900 4700 4100 3600 3250 3000 2800 2600 2500 2200 2000 1850 1700
4 4.026 17,500 12,000 9,700 8,300 7,400 6,80 6,200 5,800 5,400 5,100 4,500 4,100 3,800 3500
Nominal
Iron Pipe Black Iron Pipe
Size, Length of Pipe, Feet
Inches 10 20 30 40 50 60 70 80 90 100 125 150
1/2 275 189 152 129 114 103 96 89 83 78 69 63
3/4 567 693 315 267 237 217 196 185 173 162 146 132
1 107 732 590 504 448 409 378 346 322 307 275 252
1 1/4 220 149 121 103 913 834 771 724 677 630 567 511
1 1/2 330 229 185 155 141 127 118 108 102 976 866 787
2 622 433 346 299 264 239 220 204 192 1811 1606 1496
Copper
Outside Length of Tubing, Feet
Diameter,
Inch 10 20 30 40 50 60 70 80 90 100
3/8 39 26 21 19 _ _____
1/2 9262 5041 37 3531292726
5/8 199 131 107 90 79 72 67 62 59 55
3/4 329 216 181 145 131 121 112 104 95 90
7/8 501 346 277 233 198 187 164 155 146 138
Fig. 4

116 720 606 518
T e water eater must be isolated from t e gas supply piping
system by closing t e manual s utoff valve during any
pressure testing of t e gas supply piping system at test
pressures equal to or more t an 0.5 psig.
T e water eater, including t e pressure regulator provided
wit it, must not be operated at gas supply pressures in
excess of 0.5 psig. If overpressure as occurred, suc as
t roug improper testing of t e gas lines or malfunction of
t e supply system, t e gas valve and regulator must be
c ecked for safe operation. Make sure t at t e regulator
vent is protected against blockage.
W en your connections are made, c eck for gas leaks at
all joints (not just t e ones you made). Apply some soapy
water to all gas fittings and gas valve. Soap bubbles are a
sign of a leak.
NOTE: Do not apply soap solution to pilot filter screen or
pilot orifice area. If you ave a leak, s ut off t e gas. After
verifying t at required gaskets are in place, tig ten
appropriate fittings to stop leak. Turn t e gas on and c eck
again wit a soapy solution. Never test for gas leaks using
a match or flame.
WATER CONNECTIONS
Install t e eater centrally in t e building if possible and
make ot water piping runs as s ort as possible W en facing
t e eater, t e cold water inlet will be on t e rig t and t e
ot water outlet on t e left..
Alt oug water piping t roug out t e building may be ot er
t an copper, copper or galvanized piping s ould be used
w en connecting to t e eaters ½” male NPT flex connectors
(follow local codes if more stringent). Plastics or ot er PEX
type plumbing line materials are not suitable for connecting
directly to t e water eater. Keep water inlet pipe to no less
t an ½” (19.05mm) diameter to allow t e full flow capacity.
If t e cold and ot connections to t e eater are reversed,
t e eater will not function.
T e Aquastar 125BS is provided wit two flexible type
connectors t at must be connected to t e fittings of t e
water valve as s own in Fig. 6. T e union end of t e flexible
connectors s ould be attac ed to t e rear inlet ports of t e
water valve wit t e supplied was er gaskets. No pipe dope
or t read tape is to be used at t ese joints.
Be certain t ere are no loose particles or dirt in t e piping.
Blow out or flus t e lines before connecting to t e water
eater. Full port valves s ould be installed on bot t e cold
water supply and ot water outlet lines to facilitate servicing
t e eater (see Fig. 7). For installation on a private well
system wit t e use of a pressure tank, t e lowest pressure
range setting recommended is 30-50 psi (2.07-3.45 bar).
Fig. 5 - Installation of Gas Pressure Regulator
T e pressure regulator provided wit t e eater is adjusted
to deliver t e proper gas pressure (as indicated on t e rating
plate and in t e manual for altitude up to 2000 feet (660
meters) above sea level. On appliances being installed above
2000 ft (660 meters) elevation, t e inlet gas pressure s ould
be set at installation to t e value s own below.
NOTE: The gas pressures specified below refer to
pressures taken at the test pressure tap on the gas inlet
pipe just above the regulator (See Fig 5). These readings
should be taken while the heater is operating at full input
— i.e. maximum water flow with the temperature dial
selector turned all the way clockwise.
MAXIMUM INLET GAS FLOW PRESSURE SETTING
Altitude Natural Gas Liquid Propane
inches W.C: inches W.C:
0' - 2.000 ft 5.7" 10.5"
2.000 ft - 4.500 ft 4.6" 8.4"
Above 4.500 ft consult your local gas supplier.
GAS INLET PIPE
PRESSURE TAP
PRESSURE REGULA-
TOR
(wit directional arrow on
reverse side pointing
upward)
PLASTIC VENT CAP
GAS LINE SIZING
-It is strongly recommended that the Natural Gas pipe
be Black Iron pipe the entire distance from the outside
meter to the inlet of the A uastar regulator. 1/2” Black
Iron pipe up to 10 feet, 3/4” Black Iron pipe up to 40 feet
and 1” Black Iron pipe up to 150 feet distances. Flex line
tubing is NOT recommended, but if used then oversize
it.
-It is strongly recommended that the LP Gas pipe be
semi-rigid copper or Black Iron pipe from the outside
regulator to the inlet of the A uastar regulator. For semi-
rigid copper piping: 5/8” up to 20 feet and 3/4” up to 60
feet distances. For Black Iron piping: 1/2” up to 45 feet
and 3/4” up to 160 feet distances. Flex line tubing is NOT
recommended, but if used then oversize it.
THESE FIGURES ARE FOR AQUASTAR SUPPLY ONLY, ALL
OTHER APPLIANCES IN THE BUILDING WILL NEED TO
BE INCLUDED IN THE PIPE SIZING.
National Fuel Gas Code requires t at a sediment trap (drip
leg) be installed on gas appliances not so equipped. T e
drip leg must be accessible and not subject to freezing
conditions. Install in accordance wit t e recommendations
of t e serving gas supplier.
WARNING: T e eater must be disconnected from t e gas
supply piping system during any pressure testing of t at
system at test pressures in excess of 0.5 psig. Fig. 6 - Water valve and water connectors, top view
WASHER
WATER FILTER
WATER VALVE
WASHER
INLET
OUTLET
FLEX
CONNEC-
TORS

12 6 720 606 518
OPERATING INSTRUCTIONS
Before proceeding wit t e operation of t e eater make
sure t at t e system is filled wit water.
Open t e cold water inlet supply to t e eater fully.
Open a ot water faucet to permit t e water to fill t e eater
and t e piping and to eliminate t e air trapped in t e system
Close t e ot water faucet after t e water flows freely and
all t e air as escaped from t e system. T e water eater
is now ready to operate.
FOR YOUR SAFETY READ BEFORE LIGHTING
THE PILOT
Warning: If you do not follow t ese instructions
exactly, a fire or explosion may result causing property
damage, personal injury or loss of life
A. T is appliance as a piezo-igniter for lig ting t e pilot
burner. W en lig ting t e pilot, follow t ese instructions
exactly.
B. BEFORE LIGHTING smell all around t e appliance area
for gas. Be sure to smell next to t e floor because some gas
is eavier t an air and will settle on t e floor.
WHAT TO DO IF YOU SMELL GAS
- Do not try to lig t any appliance.
- Do not touc any electric switc ; do not use any p one
in your building
- Immediately call your gas supplier from a neig bor’s
p one. Follow t e gas supplier’s instructions.
- If you cannot reac your gas supplier, call t e fire
department.
C. Use only your and to pus in or turn t e gas control
buttons. Never use tools. If a button will not pus in, c eck
to make sure t e buttons are being pus ed in t e proper
sequence. Follow t ese instructions exactly. If control
button(s) are jammed, close t e gas supply and call a
qualified service tec nician. Attempted forceful repair may
result in a fire or explosion.
D. Do not use t is appliance if any part as been under
water. Immediately call a qualified service tec nician to
inspect t e appliance and to replace any part of t e control
system and any gas control w ic as been under water.
LIGHTING INSTRUCTIONS (as seen on front cover
of heater)
1. STOP! Read t e safety information above on t is plate.
2. T e gas valve must be turned off by depressing t e gas
valve off button ( ).
3. Wait five (5) minutes to clear out any gas. If you smell
gas, STOP! Follow “B” in t e safety information above
on t is plate. If you don’t smell gas, go to t e next step.
4. T e pilot burner is located be ind t e peep ole in t e
front center of t e jacket directly below t is instruction
plate.
5. Depress PILOT button ( ) and lig t pilot by pus ing
PILOT INGITER button ( ). T is may ave to be
repeated.
6. Observe t e pilot flame t roug t e peep ole. T e pilot
button ( ) s ould be eld down at least 15 seconds wit
pilot burning. W en t e pilot button is released t e pilot
s ould continue to burn.
- If t e gas valve button does not pop up w en released,
stop and immediately call your service tec nician or gas
supplier.
- If pilot does not stay lit, repeat steps 1 t roug 6.
- If pilot will not stay lit after several tries, depress t e OFF
button ( ), and call your service tec nician or gas supplier.
7. W en lit, depress t e ON button ( ). T e eater will
now fire w en water is drawn at a rate greater t an t e
t res old flow rate.
NOTE: If main burner s ould fail to ignite, make sure pilot
is burning. If not, repeat lig ting steps 1 t roug 6.
TO TURN OFF GAS TO APPLIANCE
Depress t e OFF button ( ) and close t e gas supply to
t e eater.
Connecting the pressure relief valve (PRV)
A listed pressure relief valve supplied wit t e eater must
be installed at t e time of installation. No valve is to be
placed between t e PRV and t e eater. No reducing
coupling or ot er restriction may be installed in t e disc arge
line. T e disc arge line must be installed suc t at it allows
complete drainage of bot t e PRV and t e line. T e location
of t e PRV must be readily accessible for servicing or
replacement, and be mounted as close to t e water eater
as possible. See Fig 7. To install t e PRV, a suitable fitting
connected to an extension on a “T” fitting can be sweated
to t e ot water line.
Fig. 7 - Pressure Relief Valve
PIPE PRV TO
APPROPRIATE
DISCHARGE
HOT COLD

136 720 606 518
Fig. 8 - Characteristic Pilot Flame
3mm
Correct gap between pilot
burner tip and piezo electrode
tip
Piezo Electrode
Air screen filter
10mm
3/8”
Piezo
Electrode
T ermocouple
To clean the pilot burner and/ or the pilot orifice : Turn
off t e gas at t e unit. Remove t e cover of t e eater. To
do so, remove incandescent particle tray and unscrew t e
central screw located at t e bottom of t e front cover. Pull
main cover out toward you and lift up and out. Pull t e air
screen off, was it and blow any lint off (See Fig 9). T e
pilot orifices s ould also be cleaned or replaced. Do not
enlarge the orifice. Do not use any wire or s arp object to
clean orifices. Natural gas orifices are large enoug t at
you can usually clean t em by blowing t roug t em. LP
orifices, on t e ot er and, are too small to clean and s ould
be replaced. See #3 in Trouble S ooting Section. To access
t e pilot orifice, remove 2 screws olding pilot assembly in
place. T en loosen compression fittings to expose pilot
orifice.
Fig. 9 - Pilot burner with air screen/ pilot orifice
PILOT ORIFICE
AIR SCREEN
INFORMATION ABOUT WATER TEMPERATURE
T e AquaStar 125B LPS and 125B NGS water eaters
ave a gas control t at modulates burner output in response
to water flow. Its purpose is to ensure t at t e ot water
temperature will remain steady, alt oug t e water flow
demand mig t vary (down to 1/2 gal/minute). T e AquaStar
125 B”S” will produce a temperature rise of approximately
90°F at flow rates between 0.5 and 1.8 gallons per minute
unless t e water as been pre eated. If t e incoming water
is already ot, t e burners will modulate accordingly so t e
outlet temperature will not exceed 140°F.
Cold water will ave to be mixed in at t e faucet to produce
comfortable temperatures. Mixing in cold water will produce
ig er flow rates and will reduce risk of scalding. Note: 105°
is t e maximum recommended temperature for a ot bat .
Handwas ing s ould not be done in water otter t an 112°
- and cooler for older adults, young c ildren or persons wit
sensory loss. Remember t at scalding can occur in 20
seconds wit 135° water.
MAINTENANCE AND SERVICE
(see maintenance table on back of manual)
Approximately once a year, t e AquaStar s ould be c ecked
and cleaned. To remove t e front cover, first remove t e
incandescent particle tray, t en unscrew t e central screw
located at t e bottom of t e front cover. Pull main cover out
toward you and lift up and out. THE FOLLOWING
OPERATIONS SHOULD BE PERFORMED BY A
QUALIFIED SERVICE PERSON:
Vent System: S ould be c ecked annually. Clean and repair
as needed.
Water Valve (Part # 8707002393): T e water valve on
t is eater s ould be serviced periodically. Lubricate
component #27 on page 14 wit a small amount of silicon,
faucet or lit ium grease every two years to keep its o rings
fres and pus rod sliding smoot ly. Every 3-5 years replace
components #27 and #29 on page 14. T e frequency will
depend on t e mineral content of t e water and conditions
of use or w enever signs of corrosion appear at t e gas and
water valve joint. Periodically c eck t at t e water inlet filter
(#34 on page 14) is clean as well.
Pilot Flame: T e pilot flame s ould burn wit a clean s arp
blue flame and s ould resemble t e diagram in Fig 8. If t e
flame is yellow, or if t e pilot knob as to remain depressed
for a long time in order to keep t e pilot lig ted, t e pilot
burner and or t e pilot burner orifice may need to be cleaned
(NG), t e orifice may need to be replaced(LP), and or t e
air screen may need cleaning. T e pilot flame s ould envelop
approximately 10 mm (3/8") of t e tip of t e t ermocouple.
If it is too small, t e pilot burner must be cleaned. To obtain
a spark, t e position of t e Piezo igniter electrode s ould be
approximately 3 mm (1/8") from t e pilot burner tip.
Main Burner Flames: T e main burner flames s ould be
blue, wit a more intense blue cone in t e center core. Yellow
flames could be a sign of wrong size gas orifices or dirty
burners, or a blockage on t e eat exc angers fins.

14 6 720 606 518
If some burners ave yellow flames w ile ot ers ave good
flames, it is likely t at dust, lint or spider webs ave partially
clogged t e burner venturis. Contact a gas service person
to clean t e remove and clean t e burners.
Mineral Scale Build-up: T e AquaStars eater, w en
operated at lower temperatures settings, do not accumulate
mineral build-up. If owever, t e water as a ig mineral
content, periodic descaling may be necessary. T e eating
coils s ould be flus ed wit a descaling solution. Consult
your service person.
TROUBLE SHOOTING (see maintenance table)
Introduction
The quaStar 125 B “S” burners are activated by a water
flow valve. Numerous water related problems can cause
this water valve to malfunction such as: Insufficient water
flow volume to activate the burners at its minimum flow
requirement; Dirt in the water flow valve causing it to
malfunction; Sediment build-up in faucet aerators, or shower
heads; Uneven pressures between cold and hot. (with single
lever faucets) Plumbing cross overs. These water flow related
problems can cause the heater to deliver less than its full
output, or to fail to ignite or to shut down completely.
Problems are stated in upper case, bold face. Most common
causes for t e problems follow in order of likeli ood. T e
suggested solutions require t at t e cover be taken off. To
do t is, remove incandescent particle tray and unscrew t e
central screw located at t e bottom of t e front cover. Pull
main cover out toward you and lift up and out.
PILOT LIGHT WILL NOT LIGHT
1. No gas to the A uaStar
A. Gas cock on gas line may not be open.
B. Gas valve button as not been pus ed in on “PILOT”
position ( ).
C. Gas regulator may be s ut or damaged.
2. In-line A uaStar gas regulator jammed (usually on
LP gas)
Replace or unlock t e regulator. Note: T e regulator
furnis ed wit t e eater is designed for low gas pressure.
Excessive pressure will lock it up (propane only). Locking
usually appens if t e gas pressure between t e gas tank
(propane) and t e water eater’s gas regulator as not been
reduced. See page 2 for recommended correct gas pressure.
To unlock a regulator, consult your gas supplier.
3. Pilot orifice clogged and/or air screen dirty, or pilot
gas filter is dirty.
Clogging of t e pilot burner can be caused by dust and any
suspended matter contained in t e ambient air.
Alt oug t e filters can lengt en t e cleaning intervals, t ey
can never completely prevent suc clogging. In consequence
t e gas jet issuing from t e pilot orifice is reduced and or
t e air mixture is reduced. T e pilot flame is weak and t us
can no longer eat t e t ermocouple sufficiently. For cleaning
purposes, t e air filter screen is pulled off, was ed and blown
out. T e pilot orifice as likewise to be cleaned or exc anged.
Consult a gas service person to clean t e pilot.
4. Air in the Gas Line
Note: Normally t is is a problem only at t e time of initial
installation, after t e pipes ave been worked on, or after a
propane tank as been allowed to empty, or after t e eater
as been s ut down for a long time.
Bleed all t e air trapped in t e gas line. Because of t e very
small pilot orifice (especially on LP gas models), bleeding
out all t e air could take several minutes. Depress t e pilot
button ( ) and depress t is button until all t e air as
escaped, and t e gas as arrived. During t is process, press
repeatedely on t e piezo ignition button until t e pilot flame
as ignited.
PILOT LIGHTS BUT FLAME GOES OUT WHEN BUTTON
IS RELEASED
1. Pilot push button was not pushed in far enough or
was not held in long enough
Depress t e pilot button. Hold it pus ed in for at least 15
seconds to give time for t e pilot flame to properly eat t e
tip of t e t ermocouple.
2. Pilot flame improperly aimed or is too weak so it is
not properly heating the tip of the thermocouple.
T e Pilot flame s ould be a s arp blue flame and aimed at
t e tip of t e t ermocouple so t at it envelops 10 mm (3/8
“) of t e t ermocouple tip. Pilot flame as to be properly
aimed at t e t ermocouple. See Fig 8.
3. Poor thermocouple connection at the electromagnet
Note: Electromagnet is part #8707201094 located on t e
rig t side of t e gas valve be ind t e piezo pus button
assembly. C eck t e tig tness of t e t ermocouple
connection nut at t e electromagnet: T e Electro-magnet
connection is a large aluminum 17mm ex ead nut. T e
t ermocouple end is a 5 mm brass nut w ic screws into
t e 17 mm nut. Tig ten t e t ermocouple nut snugly but not
too tig t.
4. Poor circuit connections at the ECO. (Energy Cut-
Off overheat protection)
Oxidation or looseness of t e ECO terminal connections
can result in millivolt current loss t roug t e t ermocouple
safety circuit. Clean terminals wit very fine sand paper or
an eraser and reconnect ECO leads.
5. Faulty ECO (part #8707206017)
If cleaning t e terminals attac ed to t e ECO did not fix t e
problem, connect a jumper wire between t e two wires and
try to relig t t e pilot. If t e pilot flame now remains on,
replace t e ECO. If t e flame still goes out w en t e button
is released, t e ECO is not defective. Go to next step.
6. Faulty thermocouple (part #8747202083) or
electromagnet) Unless these 2 parts are at least 8 to
10 years old, it is very unlikely that they are faulty.
Before testing, reconfirm that #2 is absolutely correct,
and that all connections are clean and tight.

156 720 606 518
To test t e t ermocouple, disconnect t e t ermocouple lead
to t e ECO. Insert a multi-meter probe into t e t ermocouple
lead and attac or old t e ot er lead to t e metal gas
valve (DC common). Lig t t e pilot flame and old button,
meter reading s ould be 24 mVDC or more. If t e reading is
24 mVDC or more t e t ermocouple is good. To test t e
electromagnet, re-connect t e t ermocouple lead to t e
ECO, lig t pilot and old button w ile taking a reading
between t e ECO leads and t e metal gas valve (DC
common). T e reading s ould drop to 19 mVDC or less. If it
does not, replace t e electromagnet.
BURNERS DO NOT IGNITE WHEN HOT WATER IS TURNED
ON
1. Pilot is not on.
Lig t t e pilot. See lig ting instructions.
2. Gas valve button not positioned on Burner Position
Be sure once t e pilot flame is on, t at after a 15 to 20
second wait, t e main burner button ( ) is pus ed all t e
way in.
3. Cold incoming water connection made to wrong side
of heater
Make sure cold water inlet connection is on t e rig t side of
eater w en you are facing t e eater.
4. Water flow rate at hot water tap is too low.
Note: T e AquaStar models 125B”S” require 0.5 gallon per
minute flow to activate t e burners. T is is a flow w ic
would fill a quart jar in 30 seconds.
5. Cold water inlet filter on heater is dirty.
Remove filter and clean. T is screen filter is located at t e
inlet side of t e brass water valve (fig. 11, #34). C eck and
clean faucet aerators too.
6. Crossover in household plumbing
T e AquaStar burner activates w en t ere is sufficient water
pressure drop in t e AquaStar water valve assembly — ie.
w en a ot water faucet is opened. If t ere is a crossover in
t e plumbing, t e necessary pressure drop in t e AquaStar
will be insufficient, or totally eliminated. A plumbing crossover
can be caused by a bad was er at a single lever faucet or
incorrect plumbing or a mixing valve in t e line, etc. w ic
permits ot and cold water to mix in t e plumbing. T e
crossover will create a back pressure in t e system preventing
t e pressure drop in t e Aquastar — i.e. cold water is entering
t e water eater from bot sides and t e burners will not
come on. To confirm t ere is no crossover in t e plumbing,
s ut off t e cold water supply to t e AquaStar. Open your
ot water taps. T ere s ould not be any water flowing. If
t ere is water flowing, t ere is a crossover in t e plumbing.
T is is a plumbing problem, not an Aquastar problem. Please
contact your plumber.
7. Water valve parts may be dirty or components
damaged.
Water valve and component parts must be totally free of
dirt. First c eck t at t e venturi is free of dirt particles. In
ard water areas, mineral deposits can eventually (3 to 5
years in ard water areas) corrode t e water valve parts to
a point w ere t ey will need replacing.
ny sign of moisture or corrosion at the joint of the water
valve and the gas valve is a sign that the water valve assembly
components need to be replaced immediately.
Note: Water valve for model 125B”S” is part # 8707002393
for bot LP and NG models. (Contact service person to
clean water valve or replace if corrosion is present).
PILOT LIGHT GOES OUT DURING OR IMMEDIATELY
AFTER HOT WATER HAS BEEN USED
1. Gas pressure too low
Very low gas pressure may be caused by low delivered gas
pressure, a jammed gas regulator or undersized gas lines. If
t e gas lines are undersized, t ere may still be t e specified
static gas line pressure. However w en t e water valve
opens,and gas enters t e burners, t e pressure could drop
s arply, causing t e pilot flame to go out.
Have a gas tec nician confirm t e gas pressure bot static
and at maximum Btu output. Specifications for your eater
are on page 2.
2. Pilot may be dirty or weak
See Page 13 for instructions on pilot maintenance.
3. Burners are not shutting down immediately when hot
water is turned off
Note: If burners don’t s ut down immediately w en t e ot
water is turned off, t e eater will over eat and t e ECO
will s ut-off t e gas. Rebuild t e water valve assembly using
t e repair kit from CEC (part #8 703 406 204).
WATER IS TOO HOT
1.Water flow rate is too low.
Increase t e flow rate.
2. Not enough cold water mixing at faucet
Contact your plumber to adjust mixing valves on faucets.
3. The heater’s fixed degree rise is too high for user
T e calibration nut for t e t ermostat assembly at t e gas
valve can be adjusted upward to lower t e temperature rise.
A seal of paint coats two adjusting nuts t ere, t e t in up-
per one is a lock nut w ile t e lower one is t e adjuster.
Loosen t e lock nut one first. Tig ten t e adjuster nut in-
crementally upward and c eck water temperature, stop w en
satisfactory. T en tig ten down t e lock nut. Caution:
Never back the adjuster nut downward to the last thread
unless the thermostat is being replaced. This is a gas
seal.
WATER IS NOT HOT ENOUGH
1. Water flow rate is too high.
Decrease t e flow rate.
2. Btu input is too low due to insufficient gas pressure
It is extremely important for a tankless instantaneous
water heater to have the right size gas line to obtain
the correct gas pressure

16 6 720 606 518
See specifications on page 2. Unlike storage tank water
eaters, t e burners of a tankless water eater must be very
powerful to eat water instantaneously since t ey do t is
only at t e time ot water is actually being used. It is t erefore
imperative t at t e gas pressure requirement be met exactly.
Insufficient gas pressure will directly affect t e water
temperature at t e time of usage. See page 2 for correct
gas pressure settings.
3. Thermostat calibration is incorrect or thermostat is
defective.
Contact your service person or call CEC.
4. Btu input is too low due to insufficient gas supply
Make sure your main gas line is fully opened. If using LP
gas, be sure t at t e size of t e propane tank is adequate to
supply t e required gas pressure.
5. Cold water is mixing with the hot water between the
A uaStar and the outlet
Compare water temperature at outlet of t e AquaStar ( old
t e AquaStar’s outlet pipe wit your and) and at t e tap. If
t ese two are very different, c eck for mixing valve or
plumbing crossover (see “MAIN BURNERS WILL NOT
IGNITE...” paragrap #6).
6. Parts in water valve are dirty or damaged, which will
prevent the gas valve from being fully opened.
Water valve maintenance needs to be performed, see #7
under BURNERS DO NOT IGNITE WHEN HOT WATER
IS TURNED ON.
HOT WATER TEMPERATURE FLUCTUATES / UNIT
DEACTIVATED
1. Unbalanced pressure in waterlines
T e added restriction caused by t e Aquastar in t e ot
water system can result in uneven pressures between t e
cold and t e ot. In suc cases w en mixing cold water at
t e tap, t e lower ot water pressure may be overpowered
by a muc ig er cold water pressure, w ic may cause t e
Aquastar burners to s ut down (deactivate). Make sure faucet
aerators or s ower eads are free of minerals.
Do not add any flow restrictor to the shower head.
Typically this deactivation symptom is a result of the hot
water being too hot to use comfortably. Warm inlet water
generally causes this. Lowering the control knob setting
and/or reducing the inlet gas supply to the heater should
correct this deactivation symptom.
2. Inlet water pressure is erratic due to inade uate supply
water pressure or saturated pressure tank on well
system
For installation on a private well system wit t e use of a
pressure tank, t e lowest pressure range setting
recommended is 30-50 psi (2.07-3.45 bar). Confirm t at
t e pressure tank is not water logged.
3. Cold water is mixing with the hot water between the
A uaStar and the outlet
See #6 under “MAIN BURNERS DO NOT IGNITE WHEN
HOT WATER TURNED ON”.
4 . Insufficient gas pressure
Note required gas pressures (page 2) and consult gas service
person.

176 720 606 518
1. Heat exc anger
2. Pilot assembly
3. Burner manifold gas
pressure test nipple
4. Main gas burner
5. Pilot gas tubing
6. Gas valve
7. Piezo igniter
8. Location of pressure tap
screw
9. Water valve
10. Gas inlet gas pressure
test nipple
5
1
4
7
9
3
10
6
2
8
Fig. 10 - Diagram of A uaStar 125 BS

18 6 720 606 518
AQ 125 BS
Fig. 11 - INTERIOR COMPONENTS DIAGRAM AND PARTS LIST

196 720 606 518
Fig. 11
INTERIOR COMPONENTS DIAGRAM
AND PARTS LIST 125BS
1Cover 8 705 421 033
2Cap cover 8 703 304 011
3Water connection gasket 8 710 103 043
4Draft divertor 8 705 505 354
5Heat exc anger 8 705 406 189
6Hot water pipe 8 700 705 431
7Cold water pipe 8 700 705 294
8Heat exc anger was er 8 710 103 045
9Over eat sensor (ECO) 8 707 206 017
10 Main burner assembly 8 708 120 296 LP
Main burner assembly 8 708 120 298 NG
11 Pilot burner assembly 8 718 105 051
11a Pilot filter screen 8 700 507 055
12 Piezo electrode 8 708 107 002
13 Pilot orifice 8 708 200 005 NG
Pilot orifice 8 748 200 173 LP
14 Pilot Tube 8 710 707 166
15 T ermocouple 8 747 202 083
16 Burner assembly was er 8 710 103 060
17 Gas valve 8 707 011 467 LP
Gas valve 8 707 011 469 NG
18 Gas supply pipe 8 700 705 464
19 Electromagnet 8 747 201 094
20 Electromagnet was er 8 700 103 144
21 Gas filter 8 700 507 051
22 T ermocable 8 747 202 078
23 T ermostat 8 707 206 039
24 O ring T ermostat 8 700 205 101
25 O ring T ermostat 8 700 205 041
26 Water valve assembly 8 707 002 393
27 Pus rod 8 703 406 204
28 Water valve diap ragm 8 700 503 050
29 Slow ignition valve 8 708 503 062
30 Water valve setting screw 8 703 404 092
31 O ring setting screw 8 700 205 050
32 Water valve venturi 8 708 205 235
33 Water valve piston assembly 8 708 500 230
34 Water inlet filter 8 700 507 059
35 Water elbow fitting 8 700 703 114
36 Water valve set screw 8 703 401 051

20 6 720 606 518
Fig. 12 - Flow chart of A uastar 125 BS