Testing Gas Lines

[EvilGriff]

I am planning an install of a Mr. Heater 45K btu garage heater. Will be using 3/4 black pipe for the gas line. I have read here that you test the line with compressed air. If you put compressed air into the end of the line, how would you test the final hookup to the heater? Or do you test the majority of the line, then use a soap test on the final connection of the black pipe to the heater??

 

[MXtras]

Fill the pipe with 100PSI compressed air and a gauge. Shut it off completely and you should have no pressure loss after 24 hours. There might be slight difference in pressure due to temperature changes and there are ways to calculate that by determining the volume of the pipe and the temp difference.

Ooops - I missed part of your question. Yes - test the run and then hook up the appliance.

Make sure your air is dry, by the way.

Scott

 

[scottr]

I am planning an install of a Mr. Heater 45K btu garage heater. Will be using 3/4 black pipe for the gas line. I have read here that you test the line with compressed air. If you put compressed air into the end of the line, how would you test the final hookup to the heater? Or do you test the majority of the line, then use a soap test on the final connection of the black pipe to the heater??

EvilGriff:

Here in Mpls./St. Paul the inspectors require you to pressurize the line to 25 lbs. and hold that pressure for 1/2 hour. My inspector stood there for a half hour and watched for any drop. (I passed.)

I also used black pipe. The inspector wanted the new line run right up to the connection with the furnace, and right up to the connection to the main line (in basement) from where I would tap, and then the line capped off at each end. I actually jerry-rigged a pressure gauge/shutoff/shrader air hose fitting at the furnace end. Remember: no final connections to either the main gas line or furnace at this point!! Once the pressure test is passed, I installed union fittings at either end and made final permanent connections. At the second (last) inspection the inspector checked for these final connections as well as full operation of the furnace (as well as proper venting runs, etc.).

Scott

 

[HoosierBuddy]

While the pressure test methods will work to find most leaks, and certainly all "dangerous" leaks, unless required by code I wouldn't do that. I'd use leek-seek or another leak detection fluid on all the threads and fittings once they are under gas pressure. You'll find any "fizzer" leaks with soap that will never show up in a pressure test.

That's what I'd do. I'm not telling you what you should do.

One thing I will tell you to do is check any appliance connectors documentation to make sure they'll take your test pressure before you put 100 psi on one. Standard service pressure for natural gas is 0.25 psi. Putting 400 times that pressure on it might be a problem.

My experience is if it leaks at 25 psi...it will still leak at 0.25 psi....just not as much. In any case, you can find leaks with soap that are undetectible by any other means short of a flame ionization detector.

Phil

 

[Franz©]

Lets just hold the phone a second.
Gas valves are built to handle inches of water pressure, and hitting a gas valve with even 10 psi is an invitation to replace the valve.

Pressure testing is fine, BUT the pressure should never reach the gas valve. The line should be isolated from the apliance before testing.