Kitchen Sink Drain

[Travelin' Texans]

Originally Posted by wrapped

I think the air admittance valve needs to be higher than sink drain and I also replaced mine with a good quality valve from big box store. With sink faucet running full on and sink draining slowly unscrew th air admittance valve, if sink starts draining quickly that's the problem.

Exactly! That diagram is hopefully not the way Thor plumbed that valve? If the sink is full with that valve that low it could be leaking. It does have a check type ball in it to prevent leaking & if it's gotten stuck the sink will drain slowly.
As others have recommended change the air admittance valve to start with then work from there if not corrected.

[BuzzDoc]

Originally Posted by MLP

First check if the pipe vent is clear. Air must be behind water. The vent pipe on the roof needs to be open. Second if the pipe is horizontal and not sloping down, then it is an assembly/design error. All drain pipes need to slope 1/4 inch minimum up to three inches maximum per foot. So if there isn't at least 1/4 inch per foot, it was a assembly or design error.

Agreed. Unscrew the collar to the drain and see if you can lower the trap so the horizontal downsloping drain pipe is below the bottom of the sink drain.

[txc2936@yahoo.com]

My sink drain was backing up, slow to drain main sink.,... I just replaced with new vent valve, from e trailer parts. All good. I didn't even try to repair original vent, just replace.

I could hear the check valve moving in the original part, but i didn't want to start spraying with WD-40.