What To Consider Before Purchasing A Propane Tankless Water Heater - Propane Line Sizing

Check to make sure your propane line is sized properly.  Tankless water heaters draw many more BTU's than a tank water heater, so you will want to make sure your propane line is of the proper size and the distance the propane line is run is not too long, so the unit will function properly.  Below are tables that show the maximum propane line run by diameter for natural propane, propane (LP) with black iron pipe and propane (LP) with copper tubing.  If any other applications are sharing the line or for more specific information, please consult the National Code Fuel Chart.

Maximum length of black iron pipe run for Liquid Propane (LP)

Model	Nominal Iron Pipe Size (diameter)
	3/8"	1/2"	3/4"	1"
38B	10 ft	160 ft
1000P		100 ft	160 ft
1600P/125B, 1600H/125HX		40 ft	150 ft	150 ft
125FX		35 ft	150 ft	150 ft
RTG-53		30 ft	125 ft	150 ft
2400E, 2400EO/250SX		20 ft	80 ft	150 ft
RTG-74, GT-199		15 ft	65 ft	150 ft

 

Propane Venting Requirements
Propane Line Sizing Requirements
Propane Combustion Air Requirements