Bow vent has water in it?
#9
My kitchen sink has been making a gurgling sound recently and in looking at the DWV is see that it is a bow vent under the sink. I think when we had the kitchen remodelled the contractor may have cut down the height of the bow vent as the top elbows are just below the sink bottom which to me seems incorrect. The vent does y off to the drain but it's barely pitched to do so I suspect a little water over time has made it's way in to the vent horizontal run which is why I have this issue 5 years later.

I took the p traps off and they are clean and no visible gunk in the drain pipe so I dont think it's a partial clog causing the issue.

I cant replace the elbow where the vent goes vertical but could cut the pipe close by, drain the suspected water and add a fernco clamp to put it back together.

My second thought would be to tap a 1/4" draincock to the pipe near the elbow in the event water gets in the vent again I can drain the water like the tank on a compressor. I have tapped pvc to build my vacuum veneer press, am I asking for trouble with this approach?

I have a drop ceiling in the basement but there is a lot of hvac ductwork in the way so access is limited.



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#10
First, the elbows should be above the flood level of the sink, or if that's not possible as in an island, as high as possible (I.E touching the bottom of the countertop). In your situation the vent could be flooded by just pulling the stopper when the sink is near flood level. Isn some cases an "emergency drain" is installed connecting the bottom of the bow vent (under the floor) to a drain. This would prevent the sink from overflowing, but in your case if there was a stoppage in the sink drain, it would drain thru the vent and then siphon the water seal out of the trap which could also cause a gurgling sound while doing so. Does your kitchen sink smell like your bathroom shouldn't?
Sign at N.E. Vocational School Cabinetmaking Shop 1976, "Free knowledge given daily... Bring your own container"
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#11
I ended up cutting the pipe open and sure enough, it had water and ungodly smelling sludge. I hooked my wet dry vac to the vent pipe and sucked out about 3 gallons of water and muck.

I will need to redo the DWV under the sink as it's not high enough and I cant just cut the vent area to raise it up.

The vent does tie back in to the drain underneath but I think a good flow could allow some water to get past the Y and into the horizontal vent.

This is just one more issue of how did this pass inspection?  Sigh.


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#12
If the horizontal portion (below the floor) of the bow vent does have an "emergency drain", and it still held 3 gallons of water, then it is pitched the wrong way. There is no part of any D.W.V. system that should have standing water except for traps which are specifically designed for that reason to create a water seal of sewer gases.. Vents are installed to maintain that seal and to allow air displaced by drain water to escape.

From your photo, it looks like you will be trashing 8-10 fittings if you cut off both risers below the couplings. Re-installation may need a few less with a more intelligent approach. An easy out would be to cut the top loop free and use Fernco's to re-connect higher up. (They are available, and will seal, on the outside of a fitting hub.)
Sign at N.E. Vocational School Cabinetmaking Shop 1976, "Free knowledge given daily... Bring your own container"
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#13
Thanks for the feedback I did not know they made fernco that fit on the outside of the fitting. I would prefer go the fernco route to avoid having to redo the whole drain assembly since it's the bow vent that needs to be adjusted. Plus sink and dishwasher will be out of commission for a shorter time frame.

The horizontal vent elbow going to the vertical pipe is up in the framing and the 90 is touching the bottom of the subflooring. If anything the run near the sink needs to be lowered a little to make sure the vent is pitched better to the eye that ties in to the drain piping.
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#14
(03-20-2022, 09:59 AM)WoodworkerTom Wrote: Thanks for the feedback I did not know they made fernco that fit on the outside of the fitting. I would prefer go the fernco route to avoid having to redo the whole drain assembly since it's the bow vent that needs to be adjusted.  Plus sink and dishwasher will be out of commission for a shorter time frame.

The horizontal vent elbow going to the vertical pipe is up in the framing and the 90 is touching the bottom of the subflooring.  If anything  the run near the sink needs to be lowered a little to make sure the vent is pitched better to the eye that ties in to the drain piping.

They don't really make one to fit the hub, but it's less than 1/8" larger than 2" pipe, so a 2" x 1-1/2" fernco will fit. GE silicone first works as a lubricant, then dries to make a semi-permanent seal. There are also "fitting savers" designed to drill the pipe out of a hub. The expensive ones work exceptionally well but one to do what you need is less than $15. I don't use them often because I have another trick to save the fittings. I won't share it now because flammable fumes are not good in enclosed spaces with fire. You can Google it, but i would use the tool or hot air with an aluminum disk inside to keep the heat on the hub vs blowing down the pipe.

I'm not following you here. Looking at your picture, are you saying on the pipe on the right, there's an elbow just below the sub-floor and a wye close to it that ties back into the drain?  If that's the case, why would you suggest adding a petcock to the horizontal portion of the bow vent? And why would there be almost 3 gallons of standing water? That's about 30' of 1-1/2" pipe totally full!

Re-reading and thinking a little more, my brain now hears that the horizontal run needs to be lowered near the sink (end). That's so the horizontal run will pitch back towards the drain. Right? If I was presented with the same situation, I'd raise the bow vent inside the sink cabinet, fix the pitch, and if it ever became a problem again it would get a Studor Vent.
Sign at N.E. Vocational School Cabinetmaking Shop 1976, "Free knowledge given daily... Bring your own container"
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#15
So I bought online a fernco p1059-22 which is a 2" socket to pipe fitting.  It just arrived so I will redo the bow vent to raise it up higher.

You are correct, the pitch on the horizontal vent is at most 1" over a 14 ft run.  I am guessing the previous homeowner had issues because there is a fernco coupling on the drain and ot looks like they may have moved the vent connection to the drain, hard to say what's going on.

I just hope I never have to do that ever again, it was beyond nasty.


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#16
I ended up with a fernco on both sides so I could push the bow vent all the way up against the bottom of the counter.  All in, about 11"s higher than it previously was.


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