My house is 20 years old and built on a concrete slab. Recently water started slowly leaking from the PVC conduit that carries the gas line under the slab and to the stove in the kitchen island. After removing the seal on the interior and vacuuming the water out, it is slowly building up again. I can not determine for certain where the PVC vents on the outside but it seems to be hooked up to the plumbing vent on the roof. Never had this issue before, but did need to have the kitchen sink drain roto-rootered by a plumbing company a few weeks before this happened (sink is 4 feet away and against the wall and not in the island). Any ideas on the cause and possible fix? Condensation on the gas line from warm water vapor in the drains? Rain coming in the vent pipe? Any advice is greatly appreciated.

the pvc is not a vent.
it is a sleeve.
the gas line enters it somewhere and exits under the sink.
you or someone else has to find the beginning of this sleeve to make sure the water isn't coming in from that end.

It definitely sounds like ground water seeping through the conduit
I would assume the the gas/ conduit piping may run directly from the meter / propane tank

Leak searches are never fun, sometimes it’s better to just spend the money for a pro

It's my understanding that the end of the conduit with the gas line under the island needs to be sealed (which it is) and the other needs to vent to the outside, incase there is ever a gas leak. A plumber tried to run a camera but could not advance more than a foot after the conduit turned up from the ground into the wall. I can't imagine ground water leaking into the conduit would make it's way up and out the pipe 2 inches above the floor without any evidence of water coming up elsewhere. Do you if code permits the conduit to be tied into the plumbing vents? Could slow flow in a pipe be backing up and reaching where they connect?

if you have a plumber with a sewer camera, why not go into the attic, cut the suspected vent and send the camera down ?

Vent for island gas line should not be tied into sewer vent.

Should look something like this -

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/[www.placerair.org]

Can you post a picture of your gas line ?

ditto curly

a gas pipe 'sleeve' MUST, repeat MUST, be sealed to gas pipe inside the structure but vented or open somewhere OUTSIDE of structure so that a gas (or water) leak will vent OUTSIDE


OP, if you truly have water coming from the gas pipe sleeve then you 'could' also have gas from a broken gas line entering - your home is now unsafe until you shut down the gas service and have the sleeve fixed

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

So the sleeve/conduit is definitely tied into the vent for the kitchen sink drain (which is against the wall 5 feet away). Some pictures are attached showing where the gas line comes up from the floor, and images from the vent. I ran a camera down the vent from the roof and the place where the plumbing vent attaches, and it had residue at the spot, likely from when the sink backed up. About 2 feet lower it makes a 90 degree bend and then hooks up to the sleeve with the gas line in it. I could not turn that corner but did get a photo from the side port of the camera showing the gas line. I have also attach a drawing of what the layout seems to be. Finally I dumped about a cup of water with red dye down the vent on the roof and it promptly collected at the bottom of the sleeve with the gas line in it. I am waiting for the sleeve to dry out (using a fan directly into it) then will try running the camera from the inside at the island and up the vent. Could this simply be from sink overflow and then rain coming down the vent?

[postimg.cc]

NFG

the sleeve for the gas line should NOT, repeat NOT, repeat NOT, be tied in to ANY part of the plumbing system


it must be SEALED to the gas pipe inside the structure and open to atmossphere 'somewhere/somehow' on the OUTSIDE





your layout is a ticking time bomb

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Natural gas or propane? Since natural gas is lighter than air, it should rise and vent to atmosphere, and if no other fixtures are tied into the vent stack except the kitchen sink, gas should not be able to accumulate in anywhere in the plumbing. Propane on the other hand is heavier than air and will not vent up a roof stack.

It is natural gas. It is sealed where the gas line comes up out of the sleeve to the island (seal is removed in the picture for inspection). The only communication is with the vent coming from the kitchen sink, which then vents to the atmosphere on the roof. I am assuming this was built to code 20 years ago when this was done since it passed all inspections.

It is STILL a ticking time bomb.

Even if 'code compliant'.



eg. Twin Towers - built to code - toppled in 45 minutes - 1/2 hour fireproofed steel (i helped build same, i know)


Empire State building - built to best practice - 4 hr fireproofed steel - fire from a B-27 direct hit circa the '40s (yes, the fully fueled plane itself on the way to land @ Maguire AFB in dense fog) self extinguished in under 3 hours with minimal LOCAL damage

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Quote

It is natural gas. It is sealed where the gas line comes up out of the sleeve to the island (seal is removed in the picture for inspection). The only communication is with the vent coming from the kitchen sink, which then vents to the atmosphere on the roof. I am assuming this was built to code 20 years ago when this was done since it passed all inspections.

It was/is not, repeat not, sealed since it leaked water alerting you to the issue.

IF there had been a significant gas leak it would / could have leaked gas into your closed island cabinetry.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Have to admit that's a unique setup. You can only assume it passed inspection if it was like that when the house was built and wasn't modified since. Gas notwithstanding, the real question is what to do about water coming down the roof vent? I would suggest a roof vent cap (google same) similar to a chimney cap, that keeps out the water. You are still subject to leaks when the kitchen sink backs up though.

Safety aside, this is certainly not best practice as Bern points out. I am not a plumber but Bern has 40+ years as a professional in the trade so we respect his (mostly right ) opinion around here.

... not mostly right ... i am 1/2 left ... but thank you



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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Bern
B-25 Mitchell Bomber I believe.

[rarehistoricalphotos.com]



Edited 1 times.

correct ....... again

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

So...been thinking about this one. What if the house is on a slab and the line is buried coming in under the slab so that the other end of the sleeve is not exposed to atmosphere. Is it possible that venting it thru the kitchen sink as described actually fulfills the code requirement for atmospheric venting as long as no other fixtures are attached? The gas can't go into the trap if it vents up....

no ... the sleeve must be vented outside the structure

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

This is from Scottsdale, AZ and shows that the sleeve for the gas pipe must be vented outdoors as Bern describes. I have not found anything that says that using the roof stack for the kitchen sink is an acceptable vent for a gas sleeve.
[www.scottsdaleaz.gov]

8, 9. and 10 are OUTSIDE the structure

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Exactly, and why I was posting. The question is: how did this pass inspection?



Edited 1 times.

? Because the local department of code enforcement was run by retired General Incompetence ?

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638