# Pressure testing a gas line for min and max PSI



## groga01 (Jan 29, 2008)

I am exprienced DIY, but I have new project to install a tankless water heater. The mfg requires the pressure in the gas line to be with 4. to 10.5 w.c. (aprox 1/8 to 1/2 PSI). What is the procedure for testing the gas w.c.? I know I need to disconnect the tankless water heater to do this. 

By the way, I did test the line for leaks.


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## glennjanie (Jan 29, 2008)

Welcome Groga:
A pressure guage can be bougtht or a U-tube manometer can be bought or made. Either one would need to be sealed into the pressure inside the pipe using fittings that end with an air valve like on a tire. The heater does not have to be disconnected, the pressure should remain the same with or without the heater running. That's why there is a regulator in the line. You may have a regulator and guage point inside the heater. Take the cover off and look for that before you go out to buy materials.  
Glenn


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## groga01 (Jan 29, 2008)

Hi Glen, thank you for your response. The heater does not have a perssure guage, but I do own one already. 

When I test the line for leaks I used the air value like fitting to pump pressure into the line and it did not leak. 

I needed to verify the pressure from the gas input. So tonight I attached my pressure value at the end of the line and turn the gas on. It is holding right around .25 PSI, which is what I need it to be.

I was just asking if there any specail procedures in measuring the gas volume or pressure.

Thank you again for your input.


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## triple D (Jan 31, 2008)

It sounds like you did something right.  I think your pressure and w.c. setting are set by regulator attached to side or inside of heater. No gas appliances are hooked up direct to line, and regulators are typically provided with unit. all regulators are set to work on your nat gas pressure in your home, or l.p. if thats what you have. So everything should be fine, if it is not working properly please post the exact nature of your problem, maybe we can help more. By the way, you should check your new gas line by isolating it from existing system and charging with exactly 15 p.s.i. no more no less. If it holds this for 10 hrs. or more your line is safe.


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