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Author:
DIYer-Ric (WA)
I hope I can describe this one.
In my new home (under construction), the plumber who put in the discharge pipe for my kitchen island sink ran it with no vent. It's a two inch pipe, and he says it doesn't need one, that's why he used a 2" rather than a 1-1/2.
Now is time to hook it up to the sink. It will need an S-Trap because the drain comes vertically up from the floor, nearly underneath the sink. There simply isn't room under there (small cabinet, and a small prep sink) to put an S-Trap made from 2" pipe.
So . . .
What I was planning was to use 1-1/2 pipe for the S-Trap, and put a screw-in type vent into the system. I thought I could put a piece in to allow the vent to go right a the top of the leg after the top of the S-Trap (if that makes any sense to anyone). The piece looks like a straight through, with a rounded Y coming in from one side, so the vent would either be at an angle, or I could put a 22.5 angle to straighten it up.
What occurred to me is that the vent will be fully under the sink, and will be no matter what I do.
The vent I bought has a rubber "valve" in it to prevent anything from coming "out" of it.
Will this work?
Do I really NEED the vent?
I know S-Traps can be problematic, and thought that without a vent, it could (would) create a siphon, and pull the water out of the trap. I was hoping a vent would eliminate that.
Am I all wet here?
Thanks!
-Ric
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Author:
dlh (TX)
the problem is is the trap will still be siphoned even if it is 2".
you need some type of vent and an aav (air admittance valve) which is what you described would be ok if your area allows them although i and others would prefer a loop vent for your situation but is about impossible without major demolition
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PLUMBERS "Protecting The Health Of The Nation"
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Author:
LemonPlumber (FL)
Roll the drain configuration from the bottom of the cabinet before the tee or wye for the vent to allow for both the trap and the air admittance valve to preform as required.
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Good Luck. Insulate your hot piping, although costly, it will pay you back every day.
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Author:
dlh (TX)
dont need to do all that
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PLUMBERS "Protecting The Health Of The Nation"
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Author:
LemonPlumber (FL)
Think he does .He seems to state that the sanitary tee will not allow him straight up area for the aav to set .which means he moves the drain before the san tee to allow for aav to work.
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Good Luck. Insulate your hot piping, although costly, it will pay you back every day.
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Author:
DIYer-Ric (WA)
Actually, I was putting a wye that exits about 22.5 degrees off vertical. I can correct for that with another adapter to get the AAV straight up. The AAV would be above the trap, but below the sink (has to be inside the cabinet).
I don't see any opportunity to put in a loop vent, and I don't know what you were referencing with the "roll . . ." statement.
I think the AAV is my only choice, short of dragging the rough-in plumber back & forcing him to put the vent in like he should have to begin with. In my mind, simply going to a 2" pipe will not solve the siphon problem.
FWIW: The sink is about 3-4' from the main drain line that is ties into. That line is vented. I'm not certain of the distance, as I'd have to crawl under the house to measure it. But it's roughly 3-4'
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Author:
LemonPlumber (FL)
You will want the aav as high in the cabinet as it will go nearer the top the better.but above the drain outlet at the minimum or it will fail.
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Good Luck. Insulate your hot piping, although costly, it will pay you back every day.
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Author:
kdog1 (OH)
could be a combination drain and vent system,you could use a 2" by 1 1/2" 90 elbow and a 1 1/2 p-trap to catch sink drain.a dry vent has to be installed somewhere in the branch line to make this acceptible,also no disposal can be hooked to it. this is legal according to IPC.without being there not sure what you have.
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Author:
PlumberManDan (IA)
Your plumber is correct KIND OF. You DO NOT NEED to use a 2" anything other than a 2 x 1.5 coupling and a 1.5" trap adapter then you can use a REAL trap NOT an S-Trap. Plus since it was a "plumber" that put it in call the local inspection official and have them look at it before it gets rocked in that way the "plumber" can cut it out and do it correctly
 PlumbCat TM 2003
Plumbermandan
Edited 1 times.
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Author:
dlh (TX)
without a vent wont it be an s-trap? i think so and unless the whole system was set up as a combination waste vent just making the one sink a 2" line does not make it a combination waste vent. not to mention that you can not install a food waste disposer with that type of system. not that most on here like them other than for revenue
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PLUMBERS "Protecting The Health Of The Nation"
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Author:
PlumerDan (CA)
what's the problum? is this work permited? if so call the local athority and get the scoop. if it's legal,no prob...if not he'll be making it so.maybe talk with the inspector who does your area....we used to be able to run 3 in over and up then a 3x1 1/2 tee for the sink with a clean out on the top(now days this could be a auto vent i supposed)anyway the 3 in was your combo waste and vent.
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Author:
dlh (TX)
now ill go with a 3" pipe as long as the rest of the system is also over sized as that is what a combo waste and vent system requires
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PLUMBERS "Protecting The Health Of The Nation"
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