I have a kitchen sink that is on a peninsula cabinet. That is, it is not
a complete island, and the plumbing comes to it through the half-wall
behind it. The original construction had a bar level counter behind the
sink, sort of giving it about a foot of back-splash wall. The vent(1
1/2" pipe) for the drain(2") goes up about 14 inches from where the sink
drain joins the vertical drain pipe and then elbows to run horizontally
to the full height wall where it then elbows to the vertical to go to the
roof. The horizontal run (1 1/2" pipe) is just slightly above the top of
I want to lower this horizontal run (3 1/2') about six inches so that I
can lower this wall, so I can make the bar flush with the rest of the
counter and the sink top when I install new counter tops. The horizontal
run will still be about 8 inches above where the sink drain joins the
vertical drain pipe. There is nothing joining this vent pipe between this
sink and the roof.
Is this a problem?
I've seen on the web where a horizontal vent pipe is supposed to be 6
inches above the flood level of the sink, but I want to beleive that this
one does not qualify as horizontal since it really, ultimately, proceeds
un-interupted to the roof.