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Nominal Iron Pipe Length of Pipe, Feet
Size, in.
1/2
3/4
1
1-1/4
1-1/2
132
278
520
1050
1600
92
190
350
730
1100
73
152
285
590
890
63
130
245
500
760
56
115
215
440
670
50
105
195
400
610
46
96
180
370
560
43
90
170
350
530
40
84
160
320
490
38
79
150
305
460
34
72
130
275
410
31
64
120
250
380
28
59
110
225
350
26
55
100
210
320
10 20 30 40 50 60 70 80 90 100 125 150 175 200
TABLE 1
NATURAL GAS PIPE CAPACITY TABLE (CU. FT./HR)
Capacity of gas pipe of different diameters and lengths in cu. ft. per hr. with pressure drop of 0.3 in. and specific gravity
of 0.60 (natural gas).
After the length of pipe has been determined, select the pipe size which will provide the minimum cubit feet per hour required for the
gas input rating of the water heater. By formula:
Gas Input of Water Heater (BTU/HR)
Heating Value of Gas (BTU/FT³)
The gas input of the water heater is marked on the water heater data plate. The heating value of the gas (BTU/FT3) may be determined
by consulting the local natural gas utility.
Cu. Ft. Per Hr. Required =
Nominal Iron Pipe Length of Pipe, Feet
Size, in.
1/2
3/4
1
1-1/4
275
576
1071
2205
189
393
732
1496
152
315
590
1212
129
267
504
1039
114
237
448
913
103
217
409
834
96
196
378
771
89
185
346
724
83
173
322
677
78
162
307
630
69
146
275
567
63
132
252
511
10 20 30 40 50 60 70 80 90 100 125 150
TABLE 2
LP GAS CAPACITY TABLE
Maximum capacity of pipe in thousands of BTU per hour of undiluted liquefied petroleum gases (at 11 inches water column pressure).
Based on a Pressure Drop of 0.5 Inch Water Column.
Example: Input BTU requirement of the water heater, 100,000 BTUH
Total pipe length, 80 feet = 3/4" IPS required.
Additional tables are available in the latest edition of the "National Fuel Gas Code", ANSI Z223.1
Gas Pressure Testing
Important: This water heater and its gas connection
must be leak tested before placing the appliance in
operation.
· If the code requires the gas lines to be tested at
a pressure exceeding 14 W.C., the water heater
and its manual shutoff valve must be disconnected
from the gas supply piping system and the line
capped.
· If the gas lines are to be tested at a pressure less
than 14 W.C., the water heater must be isolated
from the gas supply piping system by closing its
manual shutoff valve.
U.L. recognized fuel gas and carbon monoxide (CO)
detectors are recommended in all applications and
should be installed using the manufacturers instructions
and local codes, rules, or regulations.
Note: Air may be present in the gas lines and could
prevent the pilot from lighting on initial start-up. The gas
lines should be purged of air by a qualified service
technician after installation of the gas piping system.
Explosion Hazard
Have a qualified person make sure L.P.
gas pressure does not exceed 13 water
column.
Failure to do so can result in death,
explosion, or fire.