Drazice OKC 300 NTR/1 MPa Specification sheet

OPERATION AND
INSTALLATION MANUAL
STORAGE TANKS
OKC 300 NTR/1 MPa OKC 300 NTRR/1 MPa
OKC 400 NTR/1 MPa OKC 400 NTRR/1 MPa
OKC 500 NTR/1 MPa OKC 500 NTRR/1 MPa
OKC 750 NTR/1 MPa OKC 750 NTRR/1 MPa
OKC 1000 NTR/1 MPa OKC 1000 NTRR/1 MPa
Družstevní závody Dražice - strojírna s.r.o.
Dražice 69, 294 71 Benátky nad Jizerou
tel.: +420 / 326 370 990
fax: +420 / 326 370 980
e-mail: [email protected]

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CONTENT
1 TECHNICAL SPECIFICATION OF PRODUCT ................................................................................................. 4
1.1 FUNCTION DESCRIPTION ................................................................................................................... 4
1.2 PRODUCT DESCRIPTION .................................................................................................................... 4
1.3 TECHNICAL PARAMETERS.................................................................................................................. 5
1.3.1 TECHNICAL PARAMETERS OF STORAGE TANKS WITH ONE EXCHANGER.................................. 5
1.3.2 TECHNICAL PARAMETERS OF STORAGE TANKS WITH TWO EXCHANGERS............................... 6
1.3.3 PERFORMANCE DATA................................................................................................................ 7
1.3.4 PRESSURE LOSSES...................................................................................................................... 9
1.4 CONSTRUCTION AND GENERAL STORAGE TANK DIMENSIONS ...................................................... 10
2 OPERATION AND FITTING INSTRUCTION................................................................................................. 15
2.1 OPERATING CONDITIONS ................................................................................................................ 15
2.2 CONNECTING A STORAGE TANK TO A HOT WATER DISTRIBUTION ................................................ 15
2.3 PLUMBING FIXTURE......................................................................................................................... 16
2.4 CONNECTING A STORAGE TANK TO A HEATING SYSTEM................................................................ 17
2.5 PUTTING THE STORAGE TANK INTO OPERATION............................................................................ 18
2.6 PUTTING OUT OF SERVICE, DISCHARGE .......................................................................................... 19
2.7 INSPECTION, MAINTENANCE & CARE FOR THE APPLIANCE ............................................................ 20
2.8 SPARE PARTS.................................................................................................................................... 21
3 IMPORTANT NOTICES .............................................................................................................................. 21
3.1 INSTALLATION REGULATIONS.......................................................................................................... 21
3.2 DISPOSAL OF PACKAGING MATERIAL AND FUNCTIONLESS PRODUCT ........................................... 22
4 ASSEMBLY GUIDE FOR ZIP-FASTENER INSULATION (FOR 750 AND 1000 LITRES)................................... 23

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Meaning of pictograms used in Manual
Important information for storage tank users.
Recommendations of manufacturer, observance of which will ensure trouble-free
operation and long service life of the product.
CAUTION!
Important notice to be observed.
READ CAREFULLY THE BELOW INSTRUCTIONS PRIOR TO THE INSTALLATION
OF THE STORAGE TANK!
Dear Customer,
The Works Cooperative of Dražice – Machine Plant, Ltd., would
like to thank you for your decision to use a product of our
brand. With this guide, we will introduce you to the use,
construction, maintenance and other information on electrical
storage tanks.
The manufacturer reserves the right for engineering modification of the product. The product is designed
for permanent contact with drinkable water.
It is recommended to use the product in indoor environment with air temperatures from +2°C to 45°C
and a relative humidity up to 80%.
Product’s reliability and safety is proven by tests implemented by the Engineering Test Institute in Brno.

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1TECHNICAL SPECIFICATION OF PRODUCT
1.1 FUNCTION DESCRIPTION
Indirect stationary storage tanks lines NTR and NTRR are used for water heating in conjunction with
another source of heating water, most often a gas boiler. The NTRR types combine two sources of heating
water (gas boiler + a solar system or a heat pump). Their nominal performance provides sufficient amount
of hot water for large flat units, premises, restaurants, and similar establishments.
In case of increased hot water consumption, these storage tanks heat water continuously, operating
similarly to flow heaters.
1.2 PRODUCT DESCRIPTION
The tank is welded from a steel sheet; it is entirely coated with hot water resistant enamel. Magnesium
anode is added in the vessel as an additional protection against corrosion, which regulates the electric
potential of the inside of the vessel and thus reduces the effects of corrosion. Inside the tank, hot and cold
water and circulation pipes; a thermostat well; and either one or two spiral steel pipe heat exchangers
(enamelled on the outside) are all welded on.
The pipe heat exchanger is only intended for the heating circuit.
On the heater side, there is a cleaning and revision opening ending with a 110 mm flange; the clearance
including eight M8 bolts is 150 mm - 300 to 500 litres, for 180 mm clearance the spacing of ten bolts is 225
mm - 750 to 1000 litres. A heating unit with various outputs containing an operating and safety thermostat
can be mounted in the opening. The NTR series storage tanks are equipped with a G 1 1/2“ aperture for in-
screwing an additional heating element. Such version is used when the storage tank is connected to either
a solar system or a system with a heat pump, to heat water in the upper part of the storage tank to the
temperature required. The tank is insulated with 50-80 mm of polyurethane freon-free foam. The tank shell
is made of a steel sheet painted with a powder coating (the 400-500 l types only, other are in plastic), and
the connecting parts are metal-coated.

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1.3 TECHNICAL PARAMETERS
1.3.1 TECHNICAL PARAMETERS OF STORAGE TANKS WITH ONE EXCHANGER
TYPE
OKC 300
NTR/1 MPa
OKC 400
NTR/1 MPa
OKC 500
NTR/1 MPa
OKC 750
NTR/1 MPa
OKC 1000
NTR/1 MPa
Tank capacity
l
300
385
485
750
975
Diameter
mm
670
700
700
910
1010
Weight
kg
108
123
173
253
337
Operating hot service
water pressure
MPa
1
1
1
1
1
Operating heating
water pressure
MPa
1,6
1,6
1,6
1,6
1,6
Max temperature of
heating water
°C
110
110
110
110
110
Max temperature of
hot service water
°C
95
95
95
95
95
Exchanger heat
surface
m2
1,5
1,8
1,9
3,7
4,5
Exchanger
performance at
temperature drop
80/60 °C
kW
35
57
65
99
110
Performance number
according to DIN 4708
NL
8
15,2
19,1
30,5
38,8
Permanent HSW*
performance
l/h
1100
1395
1590
2440
2715
HSW* heating time
by exchanger at
temperature drop
80/60 °C
min
24
20
23
24
26
Standing loss
W
83
114
127
* HSW - Hot service water 45 °C
Table 1

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1.3.2 TECHNICAL PARAMETERS OF STORAGE TANKS WITH TWO EXCHANGERS
TYPE
OKC 300
NTRR/1
MPa
OKC 400
NTRR/1
MPa
OKC 500
NTRR/1
MPa
OKC 750
NTRR/1
MPa
OKC 1000
NTRR/1
MPa
Tank capacity
l
295
380
470
750
995
Diameter
mm
670
700
700
910
1010
Weight
kg
124
144
183
245
315
Operating hot service
water pressure
MPa
1
1
1
1
1
Operating heating
water pressure
MPa
1,6
1,6
1,6
1,6
1,6
Max temperature of
heating water
°C
110
110
110
110
110
Max temperature of
hot service water
°C
95
95
95
95
95
Upper exchanger
heat surface
m2
1
1,05
1,3
1,17
1,12
Lower exchanger
heat surface
m2
1,5
1,8
1,9
1,93
2,45
Lower/upper
exchanger
performance at
temperature drop
80/60 °C
kW
35/27
57/31
65/40
60/33
76/32
Performance number
according to DIN
4708 upper
exchanger
NL
2,9
3,4
5,9
6,2
7,1
Performance number
according to DIN
4708 lower
exchanger
NL
4,2
15,2
19,1
21
26
Permanent HSW
performance* of
lower exchanger
l/h
1100
1395
1590
1460
1490
Permanent HSW
performance* of
upper exchanger
l/h
670
740
970
815
780
HSW* heating time by
exchanger at
temperature drop
80/60 °C (lower/upper)
min
24/16
20/14
23/16
37/28
43/37
Standing loss
W
83
113
137
*HSW - Hot service water 45 °C

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cwt = 10°C cwt =10°C hwt = 45°C
mth= 50°C mth = 60°C mth = 50°C mth = 60°C
UE LE UE LE
°C - - - - l/h kW l/h kW l/h kW l/h kW l/10min l/10min m3/h
50 1,1 1,8 - - 431 17,1 259 10,4 - - - - 111 -
60 1,3 2,2 1,6 2,6 594 24 348 14,1 446 18 261 10,6 127 152
70 1,7 2,7 2 3,3 818 33,6 468 19,1 614 25,2 351 14,3 145 174
80 2,1 3,4 2,5 4,1 1086 44,2 629 25,9 815 33,2 472 19,4 166 199
90 2,7 4,4 3,2 5,3 1299 52,6 757 30,6 974 39,5 568 23 161 217
50 3,2 5,3 - - 493 19,6 305 12,2 - - - - 221 -
60 3,7 6 4,4 7,2 679 27,4 410 16,6 509 20,6 308 12,4 243 292
70 4,2 6,9 5 8,2 935 38,4 551 22,5 701 28,8 413 16,9 268 321
80 4,8 7,8 5,7 9,4 1241 50,5 740 30,5 931 37,9 555 22,9 294 353
90 5,8 9,6 7 11,5 1485 60,1 891 26 1114 45,1 668 19,5 316 379
50 3,8 6,2 - - 583 23,5 395 15,9 - - - - 332 -
60 4,7 7,8 5,7 9,3 790 32 531 21,5 593 24 399 16,1 360 432
70 5,9 9,7 7,1 11,7 1070 43,5 715 29,2 803 32,6 536 21,9 390 468
80 7,4 12,2 8,9 14,7 1430 58 962 39,6 1073 43,5 722 29,7 423 507
90 9 14,8 10,8 17,8 1720 70 1157 46,8 1290 52,5 868 35,1 450 540
2,7/2,7
3,0/3,0
3,0/3,0
Heating
water flow
Flow in 10 minutes
NL Power Factor
at
Permanent hot water output
Inlet
heating
water
temperatu
re
Type
LE
UE
OKC 300 NTRR/1MPa
OKC 400 NTRR/1MPa
OKC 500 NTRR/1MPa
cwt = 10°C
hwt = 45°C
hwt = 60°C
LE
UE
hwt = 45°C
Table 2
1.3.3 PERFORMANCE DATA
Table 3
UE –upper exchanger
LE–lower exchanger
cwt –cold water temperature
hwt –hot water temperature
mth –medium temperature of the
storage tank

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cwt = 10°C hwt = 45°C cwt =10°C hwt = 45°C
mth = 50°C mth = 60°C mth = 50°C mth = 60°C
°C - - l/h kW l/h kW l/10min l/10min m3/h
60 4,3 - 617 25,1 - - 290 -
70 5,3 8,4 888 36,1 622 26,8 322 403
80 5,3 8,4 1100 47,4 816 39,8 358 448
90 5,3 8,4 1451 59 1015 52,5 398 497
60 6,8 - 738 29,9 - - 399 -
70 10,1 12,8 990 43,2 745 32,1 443 554
80 10,1 15,2 1394 56,7 976 47,6 492 615
90 10,1 15,2 1733 70,4 1212 62,7 547 684
60 11,3 - 842 34,2 - - 500 -
70 15,2 15,8 1210 49,2 847 36,7 556 694
80 15,2 19,1 1584 64,4 1109 54,2 617 771
90 15,2 19,1 1965 79,9 1376 71,2 686 858
60 12,9 - 1279 52 - - 817 -
70 15,4 25,6 1828 74 1364 56 848 1060
80 18,3 30,5 2437 99 2065 84 880 1100
90 21 35 3046 124 2719 111 928 1160
60 16,6 - 1424 58 - - 862 -
70 19,7 32,8 2034 83 1518 62 908 1135
80 23,3 38,8 2712 110 2298 94 957 1197
90 27 45 3390 138 3026 123 1003 1254
OKC 400 NTR/1MPa
OKC 500 NTR/1MPa
OKC 750 NTR/1MPa
OKC 1000 NTR/1MPa
Type
OKC 300 NTR/1MPa
Inlet
heating
water
temperatur
e
NL Power Factor
at
Permanent hot water output
Flow in 10 minutes
Heating
water flow
hwt = 45°C
hwt = 60°C
cwt = 10°C
3
5
6
2,7
3
Table 4
UE –upper exchanger
LE –lower exchanger
cwt –cold water temperature
hwt –hot water temperature
mth –medium temperature of the
storage tank
NL Power Factor
Based on DIN, the expression of a normal flat is introduced for apartment houses in the FRG. Such a flat has
four rooms; it is occupied by 3.5 people; it has a bathtub, a hand basin, and a sink. Flats of other sizes,
number of occupants and different equipment are converted to normal flats using the relations given in the
standard (NL). The situation in our apartment houses, massively built until the recent past, is similar.
Flats intended for 3 to 4 people are equipped identically with normal German flats. Smaller flats tend to
have smaller bathtub or a shower; larger, so-called two-generation flats tend to have an extra hand basin.
Apartment buildings with luxury flats and high standard equipment, with higher number of fittings, or
fittings equipped with high standard drain armatures, both hot water and heat energy needs must be
adjusted.

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1.3.4 PRESSURE LOSSES

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1.4 CONSTRUCTION AND GENERAL STORAGE TANK DIMENSIONS
OKC 300 NTR/1 MPa
Figure 1
OKC 300 NTRR/1 MPa
Figure 2

- 11 -
OKC 400 NTR/1 MPa, OKC 500 NTR/1 MPa
Figure 3
OKC 400 NTR/1MPa OKC 500 NTR/1MPa
A1591 1921
B1523 1853
C1111 1264
D1 597 597
D2 700 700
E909 965
F684 695
G957 1040
H369 388

- 12 -
OKC 400 NTRR/1 MPa, OKC 500 NTRR/1 MPa
Figure 4
OKC 400 NTRR/1MPa OKC 500 NTRR/1MPa
A1631 1961
B957 1040
C275 275
D1 597 597
D2 700 700
E1523 1853
F1354 1604
G1223 1409
H1111 1264
I1006 1114
J909 965
K369 380
L220 220
M55 55
N25 25

- 13 -
OKC 750 NTR/1 MPa, OKC 1000 NTR/1 MPa
Figure 5
OKC 750 NTR/1MPa OKC 1000 NTR/1MPa
A1998 2025
B1887 1905
C1417 1490
D1 750 850
D2 910 1010
E1314 1324
F1079 1087
G288 295
H99 103
I1643 1672
J1005 1025
K375 385

- 14 -
OKC 750 NTRR/1 MPa, OKC 1000 NTRR/1 MPa
Figure 6
OKC 750 NTRR/1MPa OKC 1000 NTRR/1MPa
A1998 2025
B1005 1025
C378 387
D1 750 850
D2 910 1010
E1887 1905
F1467 1423
G1375 1375
H1242 1243
I1151 1153
J830 884
K402 411
L297 297
M99 103
N55 45
O1643 1672

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Hot water outlet
Circulation
Heating water inlet
Thermostat chamber
Heating water outlet
Cold water inlet
Hot water outlet
Heating water inlet
Thermostat chamber
Circulation
Heating water outlet
Heating water inlet
Thermostat chamber
Heating water outlet
Cold water inlet
2OPERATION AND FITTING INSTRUCTION
2.1 OPERATING CONDITIONS
The tank shall only be used in accordance with the conditions specified on the power plate
and in instructions for electric wiring. Besides legally acknowledged national regulations and
standards, also conditions for connection defined in local electric and water works have to
be adhered to, as well as the installation and operation manual.
The temperature at the place of storage tank installation must be higher than +2°C; and the
room must not freeze. The appliance has to be mounted at a convenient place; it means
that the appliance must be easily available for potential necessary maintenance, repair or
replacement, as the case may be.
2.2 CONNECTING A STORAGE TANK TO A HOT WATER
DISTRIBUTION
Scheme of storage tank´s water inputs and outputs
OKC 300 NTR/1 MPa, OKC 400 NTR/1 MPa, OKC 300 NTRR/1 MPa, OKC 400 NTRR/1 MPa,
OKC 500 NTR/1 MPa OKC 500 NTRR/1 MPa,
OKC 750 NTR/1 MPa, OKC 1000 NTR/1 MPa OKC 750 NTRR/1 MPa, OKC 1000 NTRR/1 MPa
Figure 7
The storage tank’s cold water inlet must be fitted with T-fittings with a discharge valve
for any discharge of water from the storage tank.
On the hot water input, each individually closable storage tank must have a test cock,
backflow valve, safety valve, and a manometer.

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2.3 PLUMBING FIXTURE
Each pressure hot water storage tank must have a safety valve with membrane loaded by a
spring. Nominal clearance of safety valves is defined by standard. The safety valve must be
easily accessible, as close to the storage tank as possible. The inlet pipes must have at least
the same clearance as the safety valve. The safety valve is placed high enough to secure
dripping water drain by gravity. We recommend mounting the safety valve onto a branch
pipe. This allows easier exchange without having to drain the water from the storage tank.
Safety valves with fixed pressure settings from the manufacturer are used for the assembly.
Starting pressure of a safety valve must be identical to the maximum allowed storage tank
pressure and at least 20 % higher than the maximum pressure in the water main (Table 5). If
the water main pressure exceeds such value, a reduction valve must be added to the system.
No stop valves can be put between the storage tank and the safety valve. During the
assembly, follow the guide provided by the safety equipment manufacturer.
It is necessary to check the safety valve each time before putting it into operation. It is
checked by manual moving of the membrane from the seat, turning the make-and-break
device button always in the direction of the arrow. After being turned, the button must click
back into a notch. Proper function of the make-and-break device results in water draining
through the safety valve outlet pipe. In common operation, such a check needs to be
implemented at least once a month, and after each storage tank shutdown for more than 5
days. Water may be dripping off the drain pipe of the safety valve; the pipe must be open
into the air, pointed down; environment temperatures must not drop below zero. When
draining the storage tank, use the recommended drain valve. First, close the water supply
into the storage tank.
Please find necessary pressure values in the below Table 5. For proper safety valve operation, a backflow
valve must be mounted on the inlets pipes, preventing spontaneous storage tank draining and hot water
penetrating back into the water main. We recommend that the hot water distribution from the storage
tank was as short as possible to minimise heat losses. At least one demountable joint must be mounted
between the tank and every supply pipe. Adequate piping and fittings with sufficiently dimensioned
maximum temperature and pressure values must be used.
SAFETY VALVE
OPERATING
PRESSURE
[MPa]
ADMISSIBLE
OPERATING
STORAGE
TANK
PRESSURE
[MPa]
MAX
PRESSURE IN
THE COLD
WATER PIPE
[MPa]
0,6
0,6
up to 0,48
0,7
0,7
up to 0,56
1
1
up to 0,8
Table 5

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2.4 CONNECTING A STORAGE TANK TO A HEATING SYSTEM
The storage tank is placed on the ground, next to the heating source, or in its vicinity. The heating circuit is
connected to marked inputs and outputs of the storage tank exchanger; deaerating valve is mounted in the
highest place. It is necessary to install a filter into the circuit in order to protect the pumps, the three-way
valve, and backflow flaps, and the exchanger from sedimentation. It is recommended to flush the heating
circuit before the assembly. All wiring connections must be properly insulated from heat. Should the
system work with priority heating of hot service water using a three-way valve, always follow the
installation instructions of the three-way valve’s manufacturer.
OKC 300-1000 NTR OKC 300-1000 NTRR
heated by a gas boiler with two pumps heated by a gas boiler and solar collectors
controlled by a three-way valve
Figure 8 Figure 9

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An example of a group storage tank connection for steady hot service water consumption from
all tanks using Tichelmann´s method
Figure 10
2.5 PUTTING THE STORAGE TANK INTO OPERATION
Before opening the power supply, the tank must be filled with water. The process of first
heating must be executed by licensed professional who has to check it. Both the hot water
outlet pipe and safety armature parts may be hot.
During the heating process the pressurised connection water that increases its volume due
to heating must drip off the safety valve. In non-pressurised connection water drips off the
overflow combination faucet. When heating is finished, the set temperature and the actual
temperature of consumed water should be roughly equal. After connecting the storage tank
to the water main and electrical power system, and after checking the safety valve (following
the instructions attached to the valve), the storage tank can be put into operation.
Before fist putting into service or after a longer shutdown the appliance has to be rinsed out
and flushed yet before heating is activated. Before heating starts, the tank must be
completely filled with water and the system properly flushed and vented. First heating of the
tank has to be watched.
C - Circulation
1 –Back-pressure valve
2 - Pump

- 19 -
Procedure:
1. Check both water and electric installation; for combined storage tanks, check the installation to a
hot water heating system. Check proper placement of operating and safety thermostat sensors.
The sensors must be inserted all the way in; first the operating and then the safety thermostat.
2. Open the hot water valve on the combination faucet.
3. Open the cold water inlet valve to the storage tank.
4. As soon as the water starts running through the hot water valve, the storage tank is filled and the
valve closes.
5. In case of a leakage (flange lid), we recommend fastening the flange lid bolts.
6. Fasten the electric installation cover.
7. In case of service water heating by electric energy, turn on the electricity (for combined storage
tanks, the heating water valve at the heating water entry to heating insert must be closed).
8. When heating service water with electric energy from the hot water heating system, turn the
electricity off and open the valves of heating water input and output, possibly de-aerate the
exchanger.
9. When commencing operation, flush the storage tank until the cloudiness in the water is gone.
10. Make sure to fill in properly the warranty certificate.
2.6 PUTTING OUT OF SERVICE, DISCHARGE
If the storage tank is put out of service for a longer time, or if it is not going to be used it has
to be drained and disconnected from the electric supply network on all poles. The switch for
the supply lead or the fuse cut-outs have to be shut off.
At places with permanent risk of frost the storage tank must be drained before the cold
season starts if the appliance remains out of service for several days and if the power supply
is disconnected.
Drainage of service water shall be performed after closing the shut-off valve in the cold
water supply piping (through the discharge valve for safety valve combination), and with
simultaneous opening of all hot water valves of connected fittings (water can be also drained
through safety valve; for that purpose, the safety valve is turned to the "Check" position).
Hot water may outflow during the drainage! If there is a risk of frost it has to be considered
that not only the water in the storage tank and in the hot water piping may get frozen but
also the water in the entire cold water supply piping. It is therefore advisable to drain all
fittings and piping that carry water, up to the part where the house water meter is installed
(connection of the house to water main) which is not jeopardised by frost. When the tank is
put in service again, it has to be ensured that it is filled with water and the water flowing
out at the hot water valves is free of bubbles.

- 20 -
2.7 INSPECTION, MAINTENANCE & CARE FOR THE APPLIANCE
During the heating process the water that increases its volume during the heating must
visibly drip off the safety valve outlet (in non-pressurised connection this water drips off the
combination faucet valve). In full heating (about 74°C) the volumetric water gain is approx.
3.5 % of the tank capacity. The function of the safety valve has to be checked regularly. If the
safety valve control knob is lifted or turned to the “Control” position, the water must flow
out easily, without any obstacles, from the safety valve element to the outfall line. In
common operation, such a check needs to be carried out at least once a month, and after
each storage tank shutdown that exceeds 5 days.
Caution! In doing so, the cold water supply pipe and the connection fitting of the tank may
get heated! If the storage tank does not work, or if hot water is not withdrawn, no water
shall drip off the safety valve. If water drips, then the water pressure in the supply piping is
either too high (if higher than 5.5 bars, a pressure control valve has to be fitted), or the
safety valve is defective. Please call a specialised plumber immediately!
If water contains too many minerals, an expert has to come to remove the scale that forms
inside the tank, as well as free sediments. This has to be performed after one or two years of
operation. The cleaning is carried out through the hole in the flange - dismantle the flange lid
and clean the tank. A new sealing has to be used for re-fitting. Since the inside of the storage
tank has special enamel, which must not get in contact with the scale removing agent - do
not work with a lime pump. Remove the lime layer with a timber and suck it off, or wipe it off
with a clout. After that, the appliance must be rinsed thoroughly and the heating process is
checked the same as during the initial putting in operation. Do not use any abrasive cleaning
agents (such as liquid sand, chemicals - acid, alkaline) or dye thinners (such as cellulose
thinner, trichlor, and the like) to clean the outer shell of the storage tank. For cleaning use a
wet clout and add a few drops of liquid cleaning agent for household applications. Repetitive
water heating causes limestone sediment on both the tank walls and chiefly the flange lid.
The sedimentation depends on the hardness of water heated, its temperature, and amount
of hot water consumed.
We recommend checking and cleaning the tank from scale and eventual replacement of
the anode rod after two years of operation. The anode life is theoretically calculated for two
years of operation; however, it changes with water hardness and chemical composition in
the place of use. Based on such an inspection, the next term of anode rod exchange may be
determined. If the anode is only blocked with sediments clean its surface and, if used up,
mount a new one. Have the company in charge of service affairs clean and exchange the
anode. When draining water from the storage tank, the combination faucet valve for hot
water must be open, preventing occurrence of under-pressure in the tank which would stop
water from draining.