• Tankless Water Heater expert reviews and recommendations for gas and electric Rheem, Ariston, Powerstar Stiebel Eltron and Bosch Tankless Water Heaters


Gas Tankless
Natural Gas (NG)
Propane (LP)
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Electric Tankless
PowerStar
Stiebel
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Electric Tank
Ariston
Stiebel
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Vent & Accessories
3" Venting-Bosch
3" Venting-HeatFab
4" Venting-Bosch
4" Venting-HeatFab
Covers & Valves
Miscellaneous
Thermostats
Water Filters
Water Pumps
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Gas Line Sizing For Gas Tankless Water Heaters

Check to make sure your gas 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 gas line is of the proper size and the distance the gas line is run is not too long, so the unit will function properly.  Below are tables that show the maximum gas line run by diameter for natural gas, 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 Natural Gas

Model

Nominal Iron Pipe Size (diameter)
3/8" 1/2" 3/4" 1"
Bosch 38B 20 ft 80 ft
Bosch 1000P 5 ft 20 ft 100 ft

Bosch 1600P/125B,
Bosch 1600H/125HX

 

10 ft

40 ft

150 ft

Bosch 1600F/125FX

 

10 ft

40 ft

125 ft

Bosch 2400E, 2400EO/250SX Not recommended 20 ft 70 ft

Important Factors to Consider

Gas Venting Requirements
Gas Line Sizing Requirements
Gas Combustion Air Requirements

 

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