Water in underground gas line?

[scrapmetal57]

Anyone ever run into this issue?
I installed an underground gas PE line to my garage but hit it with a trencher when I was digging for my french drain I went a little too deep. Before I spliced in a new section I think some water go in the line.
When my garage furnace is running the pressure fluctuates from 0.1 to 2.5 inH2O, static pressure is 6.0 inH20. Its an old furnace but it is definitely from the supply line into the garage. I replaced the thermocouple, gas valve, and it didn't fix anything.

My theory is that water got in the gas line and is causing a constriction so when gas flows the pressure decreases. I have a hose that I am going to try to run through the line and see if anything comes out with my shop vac.

I can post a video of the furnace in operation once I get 5 posts.

 

[OccupantRJ]

Do you have compressed air to blow the line out with? I think this would extract moisture on the tube walls better.

 

[scrapmetal57]

Do you have compressed air to blow the line out with? I think this would extract moisture on the tube walls better.

I do, but the gas line is 1 1/2" in diameter and I don't think I can get enough volume through it to do anything with the way its set up right now. My garage is a huge mess while I'm redoing it.

 

[BD1]

I do, but the gas line is 1 1/2" in diameter and I don't think I can get enough volume through it to do anything with the way its set up right now. My garage is a huge mess while I'm redoing it.

Best bet is get DRY NITROGEN . Rent a tank and high pressure regulator from welding supplier. Piping will need to be disconnected completely .

 

[OccupantRJ]

At 1-1/2”, put the vacuum on it and let it roll then. I thought it might be a much smaller line. Enough air flow will dry it out eventually. Let the vacuum blow through it first to purge it.

 

[biggziff]

I'd want to run a swab thru it sort of like cleaning a rifle bore. Since water will sit on the bottom of the pipe, you should be able to weight the cloth and pull it through anything in there.

 

[scrapmetal57]

Best bet is get DRY NITROGEN . Rent a tank and high pressure regulator from welding supplier. Piping will need to be disconnected completely .

I agree this is probably the best bet. I wasn't sure of the correct way to hook it up and I didn't want to spend money on it until I was sure that is the issue.

At 1-1/2”, put the vacuum on it and let it roll then. I thought it might be a much smaller line. Enough air flow will dry it out eventually. Let the vacuum blow through it first to purge it.

I can probably hook up my air compressor to at least flow air through it. Just not enough to blow the water out.

I'd want to run a swab thru it sort of like cleaning a rifle bore. Since water will sit on the bottom of the pipe, you should be able to weight the cloth and pull it through anything in there.

Only problem with this is that its about 50 ft of pipe and I wouldn't to risk getting anything stuck!

 

[biggziff]

I can't see removing water any other way. 80' of rope with a rag tied to it would work and would be my choice. Good luck with it.

Maybe ask a local gas company what they'd suggest?

 

[HoosierBuddy]

I have seen this many times.

When underground gas lines that only have inches on them develop small leaks, they fill with water as the ground water pressure is higher than the internal pressure.

Does that make sense?

If you have 7 inches water column of pressure in a line and 8 inches of groundwater (or more) above it....the line doesn't really leak gas out, it leaks water in.

The line fills with water and you can't get any flow.

I would tend to suspect your line is completely full of water based on your pressure readings and the fact you have a HUGE gas pipe there. 1 1/2" pipe for 50 feet? That would flow a tremendous amount of BTU's if it wasn't blocked.

So...perhaps you had a faulty repair.

How did you fix it after you cut it?

Phil

 

[scrapmetal57]

HoosierBuddy, makes total sense.
I checked the gas line with leak solution when I repaired it, but I will probably pressure test it after I am done with this. I used two couplers to splice in a new length of hose (which actually may only be 1" I dont remember). (These ones from HD.)

I'll be opening up the union at the meter to stick a hose down it later today so I'll find out whats in it.

 

[HoosierBuddy]

HoosierBuddy, makes total sense.
I checked the gas line with leak solution when I repaired it, but I will probably pressure test it after I am done with this. I used two couplers to splice in a new length of hose (which actually may only be 1" I dont remember). (These ones from HD.)

I'll be opening up the union at the meter to stick a hose down it later today so I'll find out whats in it.

I am impressed that you actually used a proper coupling for gas. I have no experience with those particular couplings though.

I have quite a bit of experience with these and they work pretty well as long as you use the right one (size) for the job. Somewhat more expensive though.

https://www.plumbersstock.com/elpcup1-1in-ips-sdr11-1-permasert-mechanical-coupling.html

 

[scrapmetal57]

I try not to do it wrong. These were just what I could get quickly. I dont expect them to be leaking. I think its just rain that got in before I could fix it.

 

[tinysparky]

If you can open the lines on both ends, you could do the bore dry method but use a electrical wire fish line and old rags.


Count how many rags you put on....then when you pull it out.

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[scrapmetal57]

If you can open the lines on both ends, you could do the bore dry method but use a electrical wire fish line and old rags.


Count how many rags you put on....then when you pull it out.

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I unfortunately didnt put a union in at the garage, just at the furnace inside the garage. I would have to fish a line up and over my garage door. One of the reasons I only want to go in one side. Lift and learn, unions are the best.

 

[Jim greengo]

I'd try a shop vac with a piece of vinyl tubing that would fit inside the line to bow it out,or **** it out.
Which ever you prefer,then I'd cap it off and pressure test it.

 

[D45]

Could pressure, volume and that huge diameter be the issue?

Did the heater run and work before you had to install a coupler?

I ran a 3/4" line almost 70 feet, 1-1/2 is crazy

 

[scrapmetal57]

Fixed it! I must have had a good bit of water in the gas line from when I hit it when the trencher.
I blew some air through the line and ended up covering the side of my house with water where the line exits the meter.
Used the shop vac with a 1/2" OD vinyl tube to **** up some more water.
Rigged up some fittings so I could hook up my compressor directly to the gas line and blew it out for 15 min (maybe 12 cfm).
Hooked up my gauge and pressure tested. Started at 20 psi and ended around 17 psi (I think the gas cooled since it's below 20F here).
Put it all back together and my garage is a nice 50F and furnace is running normally.
Thanks everyone for your help!
Be careful trenching!

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[OccupantRJ]

Good going!

 

[bullnerd]

Congrats!

Is that an old mobile home heater? Had an oil burning one in my first garage.

 

[scrapmetal57]

Congrats!

Is that an old mobile home heater? Had an oil burning one in my first garage.

Thanks! I think it's just an old home furnace. It's an AirEase from the late 80s. But it works and the heat exchanger is in good enough condition to pass inspection. If I were going to do it again I would have found a hanging garage heater. I had this, so that's what's I'm using.

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[pauls340]

I have the same problem here in Rochester Hills with moisture in line. I hooked up the shop vac and it sucked enough water out of the line, from the basement, for the furnace to run a couple of days. Tomorrow i'm replacing a 90 with a T and i'll put a blowout port where i'll hookup the compressor line....note to all, unhook line at the furnace to catch water and safe furnace.

 

[scrapmetal57]

I have the same problem here in Rochester Hills with moisture in line. I hooked up the shop vac and it sucked enough water out of the line, from the basement, for the furnace to run a couple of days. Tomorrow i'm replacing a 90 with a T and i'll put a blowout port where i'll hookup the compressor line....note to all, unhook line at the furnace to catch water and safe furnace.

Is this a one time thing? If it happens often I'd make sure the line is not leaking. I pressure tested mine so I didnt have to do this again. I think I'll come back in the Spring with a tank of dry nitrogen to make sure the line is completely dry.

 

[HoosierBuddy]

To the OP...I would not have called a 20 PSI start 17 PSI end test successful.

Yes, cooling air can cause pressure to drop immediately, but if that is the case, you would allow the line to stabilize and then monitor the pressure. Not saying you have a leak...but if the water returns...THEN you have a leak for sure.

Phil

 

[larry4406]

Post 17 picture shows galvanized fittings at the gas meter as well as black pipe.

I was off the impression that galvanized was prohibited for natural gas. Galvanized for water only.

Thoughts?

 

[scrapmetal57]

To the OP...I would not have called a 20 PSI start 17 PSI end test successful.

Yes, cooling air can cause pressure to drop immediately, but if that is the case, you would allow the line to stabilize and then monitor the pressure. Not saying you have a leak...but if the water returns...THEN you have a leak for sure.

Phil

Thanks for the insight. I'll keep an eye on it. Since its winter here I'm going to wait until it warms up to check again. If the furnace acts up then we know its a leak. So far so good.

Post 17 picture shows galvanized fittings at the gas meter as well as black pipe.

I was off the impression that galvanized was prohibited for natural gas. Galvanized for water only.

Thoughts?

I did some googling and that doesn't seem to be an older rule of thumb or local code dependent. Sometimes plumbers keep iron pipe and galvanized separate for water and gas respectively. I had it all inspected, so it is allowed by my local code.