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Gas Supply
Table 3 - Pipe-Sizing - Natural Gas
Schedule 40 Metallic Pipe (Black Iron)
Inlet System Pressure: Less than 2 PSI (55 inches W.C.)
Allowable Pressure Drop: 0.5 inches W.C.
Specific Gravity : 0.60
(Capacity in cubic feet per hour)
Length
Pipe Size (Inches)
½
¾
1
1¼
1½
10
172
360
678
1390
2090
20
118
247
466
957
1430
30
95
199
374
768
1150
40
81
170
320
657
985
50
72
151
284
583
873
60
65
137
257
528
791
70
60
126
237
486
728
80
56
117
220
452
677
90
52
110
207
424
635
100
50
104
195
400
600
Information in this chart obtained from NFPA 54, ANSI Z223.1 - 2012 Table 6.2(b)
Table 4 - Pipe-Sizing - Natural Gas
Schedule 40 Metallic Pipe (Black Iron)
Inlet System Pressure: 8.0 inches W.C. or greater, but Less than 2 PSI (55
inches W.C.)
Allowable Pressure Drop: 3.0 inches W.C.
Specific Gravity : 0.60
(Capacity in cubic feet per hour)
Length
Pipe Size (Inches)
½
¾
1
1¼
1½
10
454
949
1,787
3,669
5,497
20
312
652
1,228
2,522
3,778
30
250
524
986
2,025
3,778
40
214
448
844
1,733
2,597
50
190
387
748
1,536
2,302
60
172
360
678
1,392
2,085
70
158
331
624
1,280
1,919
80
147
308
580
1,191
1,785
90
138
289
544
1,118
1,675
100
131
273
514
1,056
1,582
Information in this chart obtained from NFPA 54, ANSI Z223.1 - 2012 Table 6.2(c)
Table 5 - Pipe-Sizing - Undiluted Propane
Schedule 40 Metallic Pipe (Black Iron)
Inlet System Pressure: 11 inches W.C.
Allowable Pressure Drop: 0.5 inches W.C.
Specific Gravity : 1.5
(Capacity in cubic feet per hour)
Length
Pipe Size (Inches)
½
¾
1
1¼
1½
10
291
608
1150
2350
3520
20
200
418
787
1620
2420
30
160
336
632
1300
1940
40
137
287
541
1110
1660
50
122
255
480
985
1480
60
110
231
434
892
1340
80
101
212
400
821
1230
100
94
197
372
763
1140
125
89
185
349
716
1070
150
84
175
330
677
1010
Information in this chart obtained from NFPA 54, ANSI Z223.1 - 2012 Table 6.3(d)
Table 2 - Pipe-Sizing - Natural Gas
Schedule 40 Metallic Pipe (Black Iron)
Inlet System Pressure: Less than 2 PSI (55 inches W.C.)
Allowable Pressure Drop: 0.3 inches W.C.
Specific Gravity : 0.60
(Capacity in cubic feet per hour)
Length
Pipe Size (Inches)
½
¾
1
1¼
1½
10
131
273
514
1,060
1,580
20
90
188
355
726
1,090
30
72
151
284
583
873
40
62
129
243
499
747
50
55
114
215
442
662
60
50
104
195
400
600
70
46
95
179
368
552
80
42
89
167
343
514
90
40
83
157
322
482
100
38
79
148
304
455
Information in this chart obtained from NFPA 54, ANSI Z223.1 - 2012 Table 6.2(a)
If this water heater is replacing an existing water heater, it
is important to verify the capacity of the gas system. Check
the capacity of the meter/regulator, and verify the pipe
lengths and sizes.
An improperly sized gas system will cause operational
issues with this water heater. Other appliances on the gas
system may be affected as well.
Flexible Gas Connectors may be used however the BTU
capacity of the connector must be checked. Each connec-
tor has a capacity label on it, verify that the connector has
a BTU capacity greater than that of the water heater. An
undersized flexible gas connector will cause operational
issues with this water heater.
Half-inch gas lines are permissible provided the gas sys-
tem meets certain requirements. First, the gas pressure
on the system must be 8.0 inch W.C. or greater. Second
the capacity of the pipe as outlined in Table 4 is followed. If
the existing pipes are too small it could cause a pressure
drop greater than 3.0 inch W.C. and will cause operational
issues with this water heater as well as other gas appli-
ances on the system.
This is an example, in US, refer to current National Fuel
Gas Code, NFPA 54 for correct pipe sizing chart, and
in Canada, refer to current Natural Gas and Propane
Installation Code CAN/CSA B149.1.
Final Considerations
