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jarvo807 06-11-2009 09:10 AM

Heating detached garage - gas supply line question
I've been asked to give quote for heating a detached garage (and bonus room above).

It appears that the person who constructed the garage layed black pipe underneath the sidewalk & driveway before the pour, housed in PVC (Electical is run this way in conduit & a separage PVC run to the garage). The line has never been hooked up nor used.

This sounds like an easy hookup, other than the fact that the end near the house (under a porch) has been exposed for a couple years, so I'm assuming moisture has entered the inside of the black pipe.

Can I flush the pipe and just use it or should I be concerned about rust on the inside and the integrity of the pipe? Should a pressure test be performed? Do you think a new gas pipe line will be required? Please help! Thanks.

SelfContract 06-11-2009 09:17 AM

Borrow your plumper's snake camera.. and runs to see it through (for rust or corosion issues also) if you care.

naptown CR 06-11-2009 09:19 AM

I would pull the black iron out and replace with the flexible stainless gas tubing that you can pull in with a fish tape. I wouldn't trust the black iron unless it is in one piece with no couplings and the conduit was graded to not allow water to sit in it. Definately clean out both pipes and set so water cannot get into ends.

jarvo807 06-11-2009 09:20 AM

Problem is it's "U" shaped and not a straight run...sorry I shoud have been more descriptive earlier.

There is about 3' vertical by the house, a 90 degree angle underground, 15' horizontal underground, a 90 degree angle underground, and 3' up into the garage.

neolitic 06-11-2009 09:27 AM

It's a problem for your
plumber or HVAC guy to
worry about.
He does the hook up, he
takes the responsibility.
Besides, he knows
what he's doing. :thumbsup:

jarvo807 06-11-2009 12:57 PM

I just need to give the homeowner an idea of the impact. If we need to lay a new gas line, concrete will need to be pulled up & it will be much more involved.

Any experience with using a gas pressure tester? I've heard 15lbs for 10 minutes is the defacto standard for inspectors when they test.

flashheatingand 06-13-2009 08:20 PM

It's highly possible, that the gas-line is good, and new piping is not necessary. It would be wise to call a local hvac guy to give you the rundown.

Remco Air 06-13-2009 10:37 PM

More than likely their is corosion inside the pipe from exposure, I would just play it safe and run a new gas line.

flashheatingand 06-14-2009 09:55 AM

Obviously we are not there. But, I would dig out the the portion of the gas run that is exposed to make sure the underground line was coated and sealed. If it was, and the section in question will hold pressure, just replace that section or pipe that you are weary of, and coat it with a little Rust-o-leum. Again, a good local guy could help determine weather it's good or not.

A new line sounds like a decent sized project that surely you and the homeowner would like to avoid if possible.

Pressure test is 30lbs, and should hold "forever".

beenthere 06-14-2009 10:30 AM

Rustoleum isn't an approved coating for underground gas lines.

Double-A 06-14-2009 10:41 AM

Are you sure its all steel all the way? From your description, it could be polyethylene with steel risers at each end.

In our area, that PVC sleeve will have to be sealed on both ends and vented.

flashheatingand 06-14-2009 11:10 AM


Originally Posted by beenthere (Post 700432)
Rustoleum isn't an approved coating for underground gas lines.

I wasn't suggesting to spray paint the underground section. Just inspect one end to make sure that it's kosher. If the exposed section is suspect, then replace and paint it. Odds are that the work was done according to code in the first place.

No need to put the homeowner through the expense if it isn't necessary.

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