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ultracrystal 11-11-2010 10:54 PM

Venting a kitchen sink
Hey guys,

I'm doing a kitchen remodel and I'm trying to figure out how to vent my sink. It's a window sink and would rather not vent the p-trap through the wall as this would require two perforations of the cabinet.

Anyways, I was thinking of draining the p-trap into a vertical line down under the floor. Down stream of this line is the septic system and up stream is a vent pipe (horizontal along the floor until it reaches a wall and goes up into the attic and out through the roof)

to septic ============================ to vent stack

Does anyone know if this setup would cause an issue? I'm in Ontario as well if that matters at all.


TheEplumber 11-12-2010 12:03 AM

199 Attachment(s)
Sounds like your making an s-trap. Would not be acceptable in my area.

ultracrystal 11-12-2010 06:03 AM

Excellent. Now that I know it's called an s-trap I've verified that I can't do this.

Thanks for the info. Back to the drawing board I go:)

plumber666 11-12-2010 07:01 AM

Crawlspace or unfinished basement? If your main drain below your kitchen is located close enough, and the pipe is high enough, you can have the p-trap below the floor, the pipe from the sink drain can go straight through the bottom of the cabinet and into the trap. Then run your horizontal part of the sink drain and tie into your main septic line.
The rules on this are: the fixture outlet pipe (from the sink to the p-trap) cannot exceed 48". The trap arm (from the trap to the main drain) must not exceed 5' for 1 1/2" pipe or 8' for 2" pipe. These are newish rules in the National Plumbing Code in Canada. Hope this makes sense, and good luck!

ultracrystal 11-12-2010 07:59 AM

My basement is unfinished (for now) and will only ever have a suspended ceiling. I was thinking about what you are proposing as well. Actually, it would be nice because it would minimze the amount of plumbing in the cabinet itself.

What about the vent though? Is it ok that the p-trap would run into a t-fitting to which a horizontal vent pipe would be connected before going up vertical?

Plumber26 11-14-2010 09:33 PM

That would be "okay" but, an even better idea would be to drill a 2'' hole in the cabinet (back corner, opposite the disposal if you have one). Then, you'll attach an end outlet waste assembly to strainers on sink and trap above the cabinet. You'll then go into a sanitary tee and pipe the part going through the cabinet into the existing drain below. On the top side of the tee, you'll run a piece of pipe up and install an air admittance valve at the top.... That will be your vent. Better this way, that way if/when your drain gets clogged, the trap can be easily removed for cleaning.

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