Suds lock? in kitchen sink drain plumbing
Our fiver, like most, has a separate gray tank for the kitchen sink. The vent going up to the roof is 8 or 9 feet away from the sink. The P trap is a couple of feet to the right of the left hand bow...
Forum Discussion
Snowman9000 wrote:
Maybe it is. I was looking at it the other way. Air needs to get out, not in, for the drain line to flow. That is what the main vent is supposed to do. But maybe the lateral needs air going in at the valve.
Wrong. The air admittance valve (AAV) is venting the "line", not the "tank". While the main tank vent (through the roof) allows air out of the tank, the AAV allows air into the drain line, to prevent a vacuum in the drain line.
I would also suggest that the same thing is likely happening without the suds; the suds sitting on top of the trapped water just makes it more obvious.
