When kitchen sink - at least half full, is drained, the water backs up in to
a sink in the basement. There is no problem if I run the kitchen faucet
without stopping the drain. The kitchen sink is vented but the sink in the
basement is not. Is there any way to resolve this problem? Venting the
sink in the basement is not practical. The basement sink seems to drain
well. I was wondering if there is such a thing as one way valve that I can
install in the basement sink drain.
To prevent siphoning of the trap, an air admittance valve (mechanical vent) lets
air into the drain line. In addition to admitting air, a conventional vent also
lets air out. Your basement sink is backing up not because air can't get in but
because the air ahead of the draining water can't get out. This means an air
admittance valve won't help. What you need on your basement sink is a vent that
leads all the way through the roof. If you tie it in to an existing vent it
connect no lower than 6" above the flood rim of the highest fixture served by
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