Proper Line Sizing

July 28 2015,

Written by Frank Erickson

Trac-pipe

It is important when installing a gas line that you size it correctly for the application. When sizing gas piping systems certain factors must be considered. Piping must be sized to supply enough gas for all appliances to operate at the same time. To determine this you must add the BTUs of all of the appliances in the system and take into consideration the type of metal the pipe is made from. As you can see below there is a chart for copper tubing size and a chart for iron pipe size with the BTU ratings for the length and diameter of the line.

Propane pipe fittings

You should also consider that the customer may want to add appliances at a later date. Gas piping should be sized in accordance with the tables in the Standard Gas Code or by other engineering methods approved by local Authority Having Jurisdiction. When sizing the gas line make sure you add 5 feet per elbow to the total length. If the gas line is undersized the appliances will operate inefficiently and could lead to equipment failure and sooting. If you are adding appliances to an existing system and are finding that the line size may be too small, install a 2 PSI regulator with Maxitrol regulators at the appliance.

Remember to pressure and leak test your systems prior to putting into service. BE SAFE!

Approximate BTU Ratings for Appliances
Appliance		Input BTU per Hour (approx.)
Range, free standing oven - Domestic		65,000
Built-in oven or broiler unit - Domestic		25,000
Built-in counter top unit - Domestic		40,000
Water Heater, Automatic instantaneous
Capacity	2 gallons per minute	142,800
	4 gallons per minute	285,000
	6 gallons per minute	428,400
Refrigerator		3,000
Clothes Dryer - Domestic		35,000
Gas Light		2,500
Gas Logs		30,000

Capacity of Pipe (BTU x 1000) at ½ psi Copper
Nominal Pipe Size COPPER (in)	Pipe Length (ft.)
Nominal Pipe Size COPPER (in)	10	20	40	80
1/4 (3/8)	35	25	17	12
3/8 (1/2)	75	50	35	25
1/2 (5/8)	150	105	70	50
5/8 (3/4)	265	180	125	85
3/4 (7/8)	380	260	180	120
1 (1 1/8)	805	555	380	260
1 1/4 (1 3/8)	1450	995	685	470

Capacity of Pipe (BTU x 1000) at ½ psi Iron Pipe
Pipe Size (in)	Pipe Length (ft.)
Pipe Size (in)	10	20	40	80	150	300
1/2	235	160	110	75	55	35
3/4	490	340	230	160	115	80
1	925	640	440	300	215	145
1 1/4	1900	1305	900	620	440	300
1 1/2	2850	1960	1345	925	660	450
2	5490	3770	2590	1780	1270	870
2 1/2	8740	6010	4130	2840	2020	1390
3	15455	10620	7300	5020	3570	2450
4	31525	21670	14890	10230	7280	5010
5	57030	39200	26940	18520	13180	9060
6	92350	63470	43620	29980	21340	14665
8	189750	130410	89630	61600	43840	30135