WarmFlow DI110UV User manual

Cylinder Manual
Incorporating: User Instructions
Installation Instructions
Commissioning Instructions
Maintenance Instructions
Nero Unvented Cylinders
Mains Pressure Stainless Steel Water Heaters
Products covered by this manual:
Direct
DI110UV
DI140UV
DI170UV
DI200UV
DI240UV
DI290UV
Indirect
IN110UV
IN140UV
IN170UV
IN200UV
IN240UV
IN290UV
Twin Coil
TW170UV
TW200UV
TW240UV
TW290UV
Heat Pump
HP170UV
HP200UV
HP240UV
HP290UV

INSTALLATION, COMMISSIONING & SERVICING
All works to this appliance including installation and commissioning must be conducted as
described herein by appropriately certified and competent persons as instructed and in
accordance with all applicable current regulations and standards. The Guarantee Registration of
the product must be completed and returned to the manufacturer with proof of purchase (e.g.
receipts / invoices).
This appliance must be serviced annually by appropriately certified and competent persons, and
proof of servicing (e.g. receipts / invoices) retained.
The complete guarantee policy statement is included in Section 9, page 32.
FAILURE TO COMMISSION, REGISTER AND ANNUALLY SERVICE THIS
PRODUCT WILL INVALIDATE ALL GUARANTEES
TECHNICAL, SPARES & GUARANTEE CLAIMS
For technical advice about the installation, commissioning, servicing or use of this appliance,
please contact the Warmflow Customer Care Centre. Please also refer to our website
www.warmflow.co.uk.
Should replacement components be required, a list of available spares is provided in Section 8.3,
page 30.
In the unlikely event that replacement components might be required within the guarantee period,
please notify the Customer Care Centre stating the serial number of the appliance, stating the
nature of the fault and the part number of the replacement components required.
Warmflow Customer Care Centre
Warmflow Engineering
Lissue Industrial Estate
Moira Road
Lisburn
BT28 2RF
Northern Ireland
Telephone
United Kingdom: 028 9262 1515
Republic of Ireland: 048 9262 1515
Email
[email protected]
Website
www.warmflow.co.uk

Page 1of 34
CONTENTS
1User Instructions.................................................................................................................2
1.1 User Warnings ...........................................................................................................................2
1.2 Cylinder Thermostat...................................................................................................................2
1.3 Immersion Thermostat ...............................................................................................................3
2Installation Requirements...................................................................................................4
3Handling and Storage .........................................................................................................5
4Standard Equipment ...........................................................................................................5
5Technical Data.....................................................................................................................5
5.1 General......................................................................................................................................5
5.2 Direct Cylinders..........................................................................................................................6
5.3 Indirect Cylinders........................................................................................................................7
5.4 Twin Coil Cylinders.....................................................................................................................8
5.5 Heat Pump Cylinders .................................................................................................................9
6Installation .........................................................................................................................10
6.1 Cylinder Location......................................................................................................................10
6.2 Hot & Cold Water Connections.................................................................................................10
6.3 Primary & Renewable Circuits..................................................................................................12
6.4 Tundish....................................................................................................................................13
6.5 Expansion Vessel.....................................................................................................................13
6.6 Pipework Configurations –Excluding Heat Pump models ........................................................14
6.7 Pipework Configurations –Heat Pump models.........................................................................15
6.8 Plate heat exchanger installation..............................................................................................16
6.9 Inlet Group connections –All models .......................................................................................17
6.10 Discharge Pipework .................................................................................................................18
6.11 Electrical Installation.................................................................................................................22
7Commissioning..................................................................................................................28
7.1 Adjustment of Immersion Thermostat.......................................................................................28
7.2 Commissioning.........................................................................................................................28
7.3 Draining....................................................................................................................................29
8Maintenance.......................................................................................................................30
8.1 Regular Maintenance...............................................................................................................30
8.2 Inspection Access ....................................................................................................................30
8.3 Replacement Parts...................................................................................................................30
8.4 Fault Finding ............................................................................................................................31
9Guarantee...........................................................................................................................32
10 End-of-Life Information..................................................................................................33
10.1 Safety Risks.............................................................................................................................33
10.2 Disassembly of the Product......................................................................................................33
10.3 Casing and key components....................................................................................................34

Page 2of 34
1 USER INSTRUCTIONS
1.1 User Warnings
Do not remove or adjust any part of this unvented water heater.
If the unvented water heaterdevelops fault, such as aflow of water from the discharge pipeswitch
the heater off.
In all cases contact a competent installer.
Documented records of annual services must be retained by the user.
If cold/warm water is discharged from the cylinder via the tundish, call your installer.
If extremely hot water is discharged, immediately switch off ALL heat sources (which may
include boilers, heat pumps, solar thermal systems and immersion heaters), isolate their
electrical supplies and call your installer.
This appliance is not intended for use by persons (including children) with reduced physical,
sensory or mental capabilities, or lack of experience and knowledge, unless they have beengiven
supervision or instruction concerning use ofthe appliance by aperson responsible fortheir safety.
Children should be supervised to ensure that they do not play with the appliance.
The recommended storage temperature for both direct and indirect cylinders is 60-65°C. In hard
water areas consideration should be given to reducing this to 50-55°C. In some applications
guidance on Legionella control and safe water delivery temperatures can require a storage
temperature of 60 - 65°C, distributing to outlets at 50 - 55°C, using thermostatic mixing valves to
control the final outlet temperature. For details consult local regulations applicable to the
installation.
When a hot tap is turned on there may be a short surge of water –this is quite normal with
unvented systems and does not mean there is a fault. When you first fill a basin, the water may
sometimes appear milky. This is due to air bubbles in the water which will clear very quickly.
1.2 Cylinder Thermostat
All cylinders (except Direct models) are fitted with one or more
cylinder thermostats to control the heat input to the cylinder from a
remote heat source, such as a boiler, heat pump or solar thermal
installation. The temperature of each cylinder thermostat is
adjustable between nominally 40°C and 70°C. Turn the control
knob clockwise to increase temperature, and anticlockwise to
decrease.
Each cylinder thermostat has a built-in manually reset safety
thermostat which will ‘lock out’ in the event of the cylinder
overheating and which will need to be reset in order to restore
operation.
In the event of a lockout situation occurring, it is vital to contact the
installer of the appliance to determine and rectify the cause of lock
out.
All electrical supplies to the appliance must be isolated before attempting to reset the thermostat.
Control dial
Reset button

Page 3of 34
1.3 Immersion Thermostat
Direct Models only
Direct model cylinders may be supplied with SMART Thermostats. SMART thermostats learn the
routine of hot water use, and adjust their operation to suit this, increasing energy efficiency.
The immersion heater with SMART thermostat must be fitted to the lowest immersion heater
position in the cylinder.
Please refer to documentation supplied with the SMART thermostat for operation and reset
information.

Page 4of 34
2 INSTALLATION REQUIREMENTS
Prior to installing this unvented hot water cylinder, please confirm that:
a) The mains water supply is capable of achieving a minimum flow rate of 20 litres per minute
at a minimum dynamic pressure of 1.5 bar at all times. If this performance cannot be
achieved the installation of an unvented cylinder may not be suitable.
b) The maximum mains supply pressure at any time does not exceed 16 bar. If this is the
case an additional ‘special’ pressure reducing valve (not supplied) may be required.
c) The mains water supply is from a public source (i.e. not from a private borehole) and that
the hardness of the water is less than 200 mg/litre. Where hardness in excess of 200
mg/litre is experienced, a suitable and effective hard water treatment must be installed.
The device should be rated for a flow rate of 50 litres per minute in order to maintain
maximum performance.
d) All circuits supplying heat to the heat exchanger coils of any cylinder (not applicable to
direct cylinders) are fully pumped (gravity circulation is NOT suitable).
e) The pipework supplying the hot water taps is capable of withstanding a maximum pressure
of 7 bar at a temperature of 90°C.
f) The mains water supply does not consistently contain a high proportion of suspended
matter that could block the strainer.
g) The mains water supply does not contain chloride levels that exceed 250mg/l.
h) This appliance must be installed vertically (not on its side) in a frost-free indoor location.
i) The cylinder will be placed on a floor area that is level and capable of supporting the
appliance when full of water.
j) All serviceable components must be accessible after installation.
k) The connection of additional pumps
The installation of this appliance is subject to the Building Regulations:
England & Wales Building Regulation G3
Scotland The Building Regulations (Scotland)
Northern Ireland Building Regulations (Northern Ireland)
Republic of Ireland Technical Guidance Document Part L
IEE Electrical Regulations
Local Water Regulations
Note: Other regulations may apply for other territories
The appliance and installation must be commissioned as described herein and the Guarantee
Registration completed and returned to the manufacturer.
FAILURE TO COMMISSION, REGISTER AND ANNUALLY SERVICE THIS
PRODUCT WILL INVALIDATE ALL GUARANTEES
Under no circumstances must the factory fitted temperature & pressure relief valve be
removed. Removal of the valve would create an extremely dangerous situation and
would invalidate all guarantees.

Page 5of 34
3 HANDLING AND STORAGE
Prior to installation this product should be handled with care and stored upright in a dry location
and in its original packaging.
4 STANDARD EQUIPMENT
Before commencing installation check that all the listed components have been supplied:
1. Temperature & pressure relief valve (factory-fitted)
2. Unvented kit including:
a. Inlet group
b. Expansion vessel
c. Tundish
d. Control thermostats and pockets
e. Immersion heater (s)
Heat pump models also include:
a. Potable water circulating pump
b. Plate Heat Exchanger arrangement
One 2-port motorised zone valve is supplied with Indirect and Twin Coil models only, for use on
the primary circuit.
Note: This stainless-steel cylinder requires no corrosion protection device e.g. anode.
5 TECHNICAL DATA
5.1 General
Direct
Indirect
Twin Coil
Heat Pump
OPERATING DATA
Operating pressure (bar)
3.0
3.0
3.0
3.0
Maximum operating / working pressure (bar)
5.5
5.5
5.5
5.5
Maximum design pressure (bar)
6.0
6.0
6.0
6.0
Maximum supply pressure to inlet group (bar)
16.0
16.0
16.0
16.0
Expansion vessel bladder pre-charge pressure (bar)
3.0
3.0
3.0
3.0
SAFETY DEVICE SETTINGS
Pressure reducing valve (bar)
3.0
3.0
3.0
3.0
Expansion valve (bar)
6.0
6.0
6.0
6.0
Cylinder thermostat limit temperature (°C)
N/A
80
80
80
Immersion thermostat limit temperature (°C)
80
80
80
80
Temperature & pressure relief (T&P) valve (°C / bar)
90/7.0
90/7.0
90/7.0
90/7.0
HEAT TRANSFER COILS
Maximum circuit temperature (renewable coil) (°C)
N/A
N/A
95
N/A
Maximum circuit temperature (other coils) (°C)
N/A
85
85
85
Maximum circuit pressure (all coils) (bar)
N/A
6.0
6.0
6.0
Table 1: General data

Page 6of 34
5.2 Direct Cylinders
Figure 1: Direct cylinders components & dimensions
DI110UV
DI140UV
DI170UV
DI200UV
DI240UV
DI290UV
DIMENSIONS
(A) Height (mm)
830
1005
1205
1380
1655
1940
(B) Secondary return connection / T&P (mm)
N/A / 530
N/A / 705
N/A / 905
1080 / 1080
1355 / 1355
1640 / 1640
(C) Upper immersion (mm)
393
481
581
668
806
948
(D) Cold inlet connection / Lower immersion (mm)
228 / 239
228 / 239
228 / 239
228 / 239
228 / 239
228 / 239
OPERATING DATA
Rated volume (litres)
107
136
165
194
233
281
Weight when full (kg)
140
180
210
240
290
350
Standing heat loss (kWh/24h)
1.43
1.41
1.68
1.78
2.08
2.15
V40 Hot water volume (litres)
138
181
230
267
345
432
PERFORMANCE
Heat up time by lower immersion only (mins)
121
154
198
237
287
345
FICHE DATA
Supplier Name
Warmflow
Supplier Model Identifier
DI110UV
DI140UV
DI170UV
DI200UV
DI240UV
DI290UV
Declared Load Profile
M
M
L
L
XL
XL
Energy Efficiency Class
C
C
C
C
C
C
Water Heating Energy Efficiency, ηwh (%)
38
38
38
38
38
38
Annual Electrical Consumption, AEC (kWh)
1339
1702
2295
2698
3609
4352
Thermostat Setting (°C)
65
65
65
65
65
65
Sound Power Level (dB)
15
15
15
15
15
15
Table 2: Direct cylinder data
Data listed with SMART Immersion thermostat fitted to lower position.

Page 7of 34
5.3 Indirect Cylinders
Figure 2: Indirect cylinders components & dimensions
IN110UV
IN140UV
IN170UV
IN200UV
IN240UV
IN290UV
DIMENSIONS
(A) Height (mm)
830
1005
1205
1380
1655
1940
(B) Secondary return connection / T&P (mm)
N/A / 558
N/A / 705
N/A / 905
1080 / 1080
1355 / 1355
1640 / 1640
(C) Primary coil upper connection (mm)
451
511
605
605
657
728
(D) Primary coil lower connection (mm)
168
228
228
228
279
351
(E) Cold inlet connection (mm)
168
228
228
228
228
228
OPERATING DATA
Rated volume (litres)
107
135
165
194
233
281
Weight when full (kg)
140
180
210
240
290
350
Standing heat loss (kWh/24h)
1.43
1.41
1.68
1.78
2.08
2.15
V40 Hot water volume (litres)
157
164
209
263
320
366
COIL PERFORMANCE (EN12897)
Primary coil rating @ 15L/min (kW)
10.15
12.91
17.51
16.81
15.72
14.66
Primary coil pressure drop @ 15L/min (mbar)
63
63
60
60
60
60
Heat up time by primary coil (mins)
23
26
25
33
42
49
FICHE DATA
Supplier Name
Warmflow
Supplier Model Identifier
IN110UV
IN140UV
IN170UV
IN200UV
IN240UV
IN290UV
Energy Efficiency Class
C
C
C
C
C
C
Standing Loss (W)
60
59
70
74
87
90
Storage Volume (litres)
107
136
165
194
233
281
Table 3: Indirect cylinder data

Page 8of 34
5.4 Twin Coil Cylinders
Figure 3: Twin Coil cylinders components & dimensions
TW170UV
TW200UV
TW240UV
TW290UV
DIMENSIONS
(A) Height (mm)
1205
1380
1655
1940
(B) Secondary return connection (mm)
N/A
1080
1355
1640
(C) Primary coil upper connection (mm)
883
988
1088
1231
(D) Primary coil lower connection (mm)
601
705
806
948
(E) Renewable coil upper connection (mm)
511
605
605
605
(F) Cold inlet connection / Renewable coil lower connection (mm)
228
228
228
228
OPERATING DATA
Cold water capacity (litres)
165
194
233
281
Weight when full (kg)
210
240
290
350
Standing heat loss (kWh/24h)
1.66
1.97
2.12
2.26
V40 Hot water volume (litres)
245
253
341
434
COIL PERFORMANCE (EN12897)
Primary coil rating @ 15L/min (kW)
14.27
14.35
14.28
14.64
Primary coil pressure drop @ 15L/min (mbar)
63
63
63
63
Heat up time by primary coil @ 15L/min (mins)
19
22
29
35
Renewable coil rating @ 15L/min (kW)
12.33
16.62
16.47
15.82
Renewable coil pressure drop @ 15L/min (mbar)
63
60
60
60
Dedicated renewable volume (litres)
83
97
117
141
FICHE DATA
Supplier Name
Warmflow
Supplier Model Identifier
TW170UV
TW200UV
TW240UV
TW290UV
Energy Efficiency Class
C
C
C
C
Standing Loss (W)
69
82
88
94
Storage Volume (litres)
165
194
233
281
Table 4: Twin Coil cylinder data

Page 9of 34
5.5 Heat Pump Cylinders
Figure 4: Heat Pump cylinders components & dimensions
HP170UV
HP200UV
HP240UV
HP290UV
DIMENSIONS
(A) Height (mm)
1205
1380
1655
1940
(B) Heat Exchanger / Secondary return connection (mm)
905
1080
1355
1640
(C) Heat Exchanger / Cold Inlet connection (mm)
228
228
228
228
OPERATING DATA
Cold water capacity (litres)
165
194
233
281
Weight when full (kg)
210
240
290
350
Standing heat loss (kWh/24h)
1.68
1.78
2.08
2.15
V40 Hot water volume (litres)
229
259
312
401
COIL PERFORMANCE (EN12897)
Primary coil rating @ 15L/min (kW)
17.08
25.85
29.38
21.92
Primary coil pressure drop @ 15L/min (mbar)
35
30
30
30
Heat up time by primary coil (mins)
25
21
22
34
FICHE DATA
Supplier Name
Warmflow
Supplier Model Identifier
HP170UV
HP200UV
HP240UV
HP290UV
Energy Efficiency Class
C
C
C
C
Standing Loss (W)
70
74
87
90
Storage Volume (litres)
165
194
233
281
Table 5: Heat Pump cylinder data

Page 10 of 34
6 INSTALLATION
6.1 Cylinder Location
The unit must be located in a frost-free, indoor location.
The unit can be fitted into a conventional airing cupboard and does not require any additional
ventilation. To maximise efficiency of the installation, surfaces of potential heat loss must be
insulated. Valves and manifolds can be insulated using manufacturer approved covers.
When selecting a location, consideration should be given to the routing of all discharge pipework
and to the relative location of the heat sources (solar panels, heat pumps or boilers) as well as to
the domestic hot water outlets –pipe runs should be kept as short as possible for maximum
efficiency of the installation.
Ensure the cylinder is positioned such that future servicing and part replacement if necessary is
possible. The installation must not prevent items such as thermostats, immersion heaters,
temperature & pressure relief valve, inlet group, pumps, heat exchangers or expansion vessel
from being removed for service or replacement.
6.2 Hot & Cold Water Connections
The factory-fitted temperature and pressure relief valve must NOT be removed from the
cylinder or tampered with in any way. The valve is pre-calibrated to operate at 7 bar or
90°C and any attempt to adjust or remove it will invalidate the guarantee and will adversely
affect the safety of the appliance.
All connections to the cylinder must be made using compression fittings. Mains supply pipework
must be a minimum of 22mm diameter to provide adequate flow rate.
Inlet group
The supplied inlet group must be fitted to the cold water mains before connection to the cold inlet
of the cylinder. When connecting the inlet group, ensure the arrow on the body is pointing in the
direction of flow (towards the cylinder).
The maximum supply pressure to the inlet group is 16 bar. If the mains supply pressure is likely
to exceed 16 bar at any time, an additional suitable pressure reducing valve (not supplied) will
be required.
A balanced cold connection is provided on the inlet group, from which the cold water supply to
the rest of theproperty can be connected in order to provide balanced supplypressure throughout
the property. If this facility is not required, the connection should be capped / stop-ended.

Page 11 of 34
Stop cock & drain
Install a full bore stop cock or ball valve (not supplied) before the inlet group assembly on the
incoming mains water supply so the unit can be isolated when required. A full bore drain cock
(not supplied) must be fitted to the supply pipework, between the cylinder and the inlet group, at
as low a level as possible. An air break must be provided at the point of drainage. (see Figure 5a
/ 5b).
Distribution pipework
Pipework supplying the hot water taps must be capable of withstanding a maximum pressure of
7 bar at a temperature of 90°C and should be run in 22mm throughout the property. Only short
lengths (max 1 metre) of 15mm should be used to connect baths, showers and basin taps etc. If
using a secondary / pumped return circuit, all pipework must be well insulated. The circulator
(bronze pump) should be time and/or temperature controlled to reduce energy consumption.
Taps & fittings pressure rating
All taps and fittings incorporated into the unvented system should have a rated operating pressure
of 7 bar or above.

Page 12 of 34
6.3 Primary & Renewable Circuits
The working pressure and temperature for all heat exchanger coils is given in Table 1. All
connections to the cylinder must be made using compression fittings.
Ensure that the correct concentration and type of corrosion inhibitor is used for the system circuits
heating the coils / heat exchanger. This must be checked concentrations adjusted as required
during annual service.
Safety thermostat
Each heat exchanger coil has an associated combined control & safety thermostat. The system
controls must be wired in such a manner as to cut off the flow of heat to the cylinder in the event
of overheating in order to comply with Building Regulations and to ensure a safe installation. This
is typically achieved using a motorised valve wired in series with the thermostat. Refer to Section
6.11 for suggested wiring schematics.
Motorised valve
A motorised valve is supplied with Indirect and Twin Coil models. This must be fitted to the
pipework supplying the primary coil (usually the coil connected to the heat source) and wired in
series with the combined control & safety thermostat in order to comply with Building Regulations
and to ensure a safe installation. In this manner, if the heat source malfunctions and produces
excess heat, the motorised valve will close preventing the cylinder from overheating. Refer to
Section 6.11 for suggested wiring schematics.
Uncontrolled solid fuel boilers and gravity circulation systems must not be used with an
unvented hot water system. For guidance on connecting a controllable solid fuel appliance (such
as a wood pellet stove or boiler) to an unvented cylinder, reference should be made to the
appliance manufacturer’s instructions and to Building Control.
Solar installations
If connecting a solar thermal installation, for example, to the renewable coilof a Twin Coil cylinder,
the controls must be wired in series with the combined control & safety thermostat.
Refer to the solar appliance manufacturer’s instructions and to Building Control for further
guidance.
Heat Pump Cylinder installations
Heat Pump cylinders can be used with a circulating pump designed for potable water installations
in conjunction with a plate heat exchanger.
The power supplyto the circulating pump is tobe controlled by the thermostat fitted to the cylinder,
refer to section 6.11.5 for details.

Page 13 of 34
6.4 Tundish
The tundish supplied must be fitted so it is visible to the occupier, away from electrical equipment,
and must be connected with copper pipe (not plastic). Guidance on the Building Regulations
requirements for the discharge pipework is provided in Section 6.10.
6.5 Expansion Vessel
An expansion vessel issupplied as part of theunvented kit and must be connected to the pipework
between the inlet group and the cylinder in order to accommodate expansion of the stored water
due to heating. For ease of installation a dedicated expansion vessel port is provided on the body
of the inlet group itself.
Ensure the expansion vessel is mounted with the connection at the bottom and that access is left
available for future servicing and removal.
Expansion vessel connections must be piped in copper.
The Expansion vessel must be mounted securely enough to support the weight of the vessel
when full.
Where a secondary return circuit is used, increased expansion capacity may be required.

Page 14 of 34
6.6 Pipework Configurations –Excluding Heat Pump models
Figure 5a: Typical pipework configuration, excluding Heat Pump models
HOT OUTLET
COLD INLET
Balanced Supply to cold taps
Discharge
M
1
2
3
4
5
Primary
Flow / Return
6
7
Mains stopcock (not supplied)
Inlet group
Temperature & pressure relief valve
Tundish
Motorised zone valve
Expansion vessel
Drain cock (not supplied)
1
2
3
4
5
6
7

Page 15 of 34
6.7 Pipework Configurations –Heat Pump models
Figure 5b: Typical pipework configuration, Heat Pump models
Pipe work accessory kits can be used to complete the installation comprising of flanged
connections, sealing washers and other fittings. Ensure the connections are clean and tight.
Additional details are included with the accessory kit, see document Q12-084.
HOT OUTLET
COLD INLET
Balanced Supply
to cold taps
Discharge
1
2
3
4
Plate Heat
Exchanger,
see Figure 5c
6
7
Mains stopcock (not supplied)
Inlet group
Temperature & pressure relief valve
Tundish
Plate Heat Exchanger
Expansion vessel
Drain cock (not supplied)
Potable water circulating pump
1
2
3
4
5
6
7
8
5
8

Page 16 of 34
6.8 Plate heat exchanger installation
The plate heat exchanger is of asymmetric design and must be fitted respecting the flow of both
potable and system (Heat Pump) water. See separate assembly document provided with the
HP cylinder kit.
There are orientation marks on the plate heat exchanger, these are to be connected to the
system water circuit.
Figure 5c: Heat Pump model plate heat exchanger connections
Potable water circulating pump installation
The circulating pump must always be installed with horizontal motor shaft. At start-up, the rotor
can must be vented by removing the plug in the top of the motor. Within a short time, the rotor
forces the remaining air out into the system via the shaft.
The circulating pump must be installed with the flow direction as marked on the pump housing
from the lower connection on the cylinder towards the plate heat exchanger, see Figure 5b for
reference.
The circulating pump must be installed with the terminal box above, or to the left or right side of
the pump.
Orientation
Marks
Potable Water
Flow
Heat Pump
Water Flow

Page 17 of 34
6.9 Inlet Group connections –All models
Figure 6: Inlet group connections
To drain
via tundish
To cylinder
‘COLD INLET’
From mains
stop cock
To cold taps
To expansion vessel

Page 18 of 34
6.10 Discharge Pipework
The following is an extract from Section G3 of the Building Regulations for England and Wales
and provides guidance on the requirements for discharge pipework. Refer also to Diagram 1.
This information is correct at time of publication of this manual. For other regions, please refer to
local guidance.
Discharge pipe D1
3.50 Safety devices such as temperature relief valves or combined temperature and pressure
relief valves (see paragraphs 3.13 or 3.18) should discharge either directly or by way of a
manifold via a short length of metal pipe (D1) to a tundish.
3.51 The diameter of discharge pipe (D1) should be not less than the nominal outlet size of the
safety device, e.g. temperature relief valve.
3.52 Where a manifold is used it should be sized to accept and discharge the total discharge from
the discharge pipes connected to it.
3.53 Where valves other than a temperature and pressure relief valve from a single unvented
hot water system discharge by way of the same manifold that is used by the safety devices, the
manifold should be factory fitted as part of the hot water storage system unit or package.
Tundish
3.54 The tundish should be vertical, located in the same space as the unvented hot water
storage system and be fitted as close as possible to, and lower than, the safety device, with no
more than 600mm of pipe between the valve outlet and the tundish (see Diagram 1).
Note: To comply with the Water Supply (Water Fittings) Regulations, the tundish should
incorporate a suitable air gap.
3.55 Any discharge should be visible at the tundish. In addition, where discharges from safety
devices may not be apparent, e.g. in dwellings occupied by people with impaired vision or mobility,
consideration should be given to the installation of a suitable safety device to warn when
discharge takes place, e.g. electronically operated.
Discharge pipe D2
3.56 The discharge pipe (D2) from the tundish should:
a. have a vertical section of pipe at least 300mm long below the tundish before any elbows or
bends in the pipework (see Diagram 1); and
b. be installed with a continuous fall of at least 1 in 200 thereafter.