American Water Heater 6510238 Gas Pressure Testing, Natural GAS Pipe Capacity Table CU. FT./HR

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 manufacturer’s 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.

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).

Nominal Iron Pipe							Length of Pipe, Feet
Size, in.	10	20	30	40	50	60	70		80	90	100	125	150	175	200
1/2	132	92	73	63	56	50		46	43	40	38	34	31	28	26
3/4	278	190	152	130	115	105		96	90	84	79	72	64	59	55
1	520	350	285	245	215	195		180	170	160	150	130	120	110	100
1-1/4	1050	730	590	500	440	400		370	350	320	305	275	250	225	210
1-1/2	1600	1100	890	760	670	610		560	530	490	460	410	380	350	320

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:

Cu. Ft. Per Hr. Required =	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.

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.

Nominal Iron Pipe						Length of Pipe, Feet
Size, in.	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	576	393	315	267	237		217	196	185	173	162	146	132
1	1071	732	590	504	448		409	378	346	322	307	275	252
1-1/4	2205	1496	1212	1039	913		834	771	724	677	630	567	511

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

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