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Old 12-08-2012, 03:18 PM   #1
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ABS in concrete slab - wet vent


My neighbor convinced me that his plumber friend is the best. The two of them installed abs pipes in a concrete slab before a pour. No way to change things now because the pipes are in the slab. They created a wet vent. A 2" abs pipe is shared by both the vent and the water runoff from a shower. I am worried because the slope is not very steep and water stays in the pipe. Are there any ways to test if air is getting through to the vent? I'm thinking of like connecting a vacuum cleaner up to the pipe and sealing it with duct tape and checking if air is getting out of the vent up on the roof. Even if air is getting out I'm worried that maybe the opening might not be big enough. Roughly 2/3 of the 2" abs pipe is filled constantly with water that just sits there and won't drain due to the slope. It eventually leads to a 4" x 2" wye at a junction down the line that then goes out to the septic tank.

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Old 12-08-2012, 03:24 PM   #2
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ABS in concrete slab - wet vent


No pipe should have standing water in it except a trap. Better put some grade on it

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Old 12-08-2012, 03:32 PM   #3
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ABS in concrete slab - wet vent


Going to have to cut the concrete out and start over.
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Old 12-08-2012, 03:50 PM   #4
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ABS in concrete slab - wet vent


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Going to have to cut the concrete out and start over.
There is no way to start over.
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Old 12-08-2012, 04:39 PM   #5
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No pipe should have standing water in it except a trap. Better put some grade on it
Can't. It's hardwired in concrete. I made a mistake to trust someone who came across as a know-it-all experienced plumber. Then the mistake was compounded when the vent pipe was built into the concrete block wall. Now there really is no clearly apparent easy work around possible.

Anyway, what are the implications of having standing water in a 2" abs pipe from a shower? What's the worst that can happen. Also, if 2/3 of the pipe roughly is standing water that means that less of it is accessible as vent. What can be the implications of that?
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Old 12-08-2012, 04:46 PM   #6
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ABS in concrete slab - wet vent


How do you know there is water standing in the pipe? If you can see it it means you do not have a trap for the shower. You better to go tho the gym to tone up for that jackhammer.
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Old 12-08-2012, 04:55 PM   #7
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ABS in concrete slab - wet vent


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How do you know there is water standing in the pipe?
I know because between the shower and the toilet there was originally supposed to be a sink. A tee for the sink was installed in the concrete. I plugged it off with a clamped rubber end cap. When I pour water into the shower all is well. It propagates down the line in the direction of the toilet then down and out the 4" abs to the septic tank. But when I take the end cap off and look down there I can see that the water is not all draining. Roughly 2/3 remains in the pipe.
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Old 12-08-2012, 05:06 PM   #8
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ABS in concrete slab - wet vent


Diagram to help you picture what's going on...

http://tj.jjt.partyconnect.me/constr...ge/badvent.jpg
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Old 12-08-2012, 05:28 PM   #9
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ABS in concrete slab - wet vent


Your toilet is vent vented through the 2" line back to the shower. My understanding (an I am not a plumber), is that it can not exceed 5' and the horizontal section must be the same size as the toilet drain.

There is no way to fix what you have without busting concrete. And while you are in there you an fix the slope on the shower.
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Old 12-08-2012, 06:20 PM   #10
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There is no way to fix what you have without busting concrete.
Well not exactly. Below is the diagram of my plan to fix things.

http://tj.jjt.partyconnect.me/constr.../fixedvent.jpg

I'm going to reserve the pipe that is in the concrete only for air/venting. No water will flow down it. I'm going to stick a wet/dry vac in there to suck up whatever water is in there now. That pipe will then be capped off and shut.

I need to install 2x6 joists and a raised floor in the place. I'm going to run a 2" pipe from the shower to the 4" abs. This will be done above-ground.

Lesson learned: don't hardwire abs pipes in concrete slabs.
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Old 12-08-2012, 07:27 PM   #11
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ABS in concrete slab - wet vent


Have you checked the line its dumping into to make sure its not clogged?
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Old 12-08-2012, 08:03 PM   #12
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ABS in concrete slab - wet vent


Personally I think it would be easier to demo the conrete and do it right. Will you maintan code required minimum ceiling height?
Even after you drain the pipe it will not stay dry. The 2" vent still does not meet code.

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