Forum Discussion
Old-Biscuit
Jan 12, 2015Explorer III
salem wrote:
Do all models have an Air Admittance Valve under the sink? I don't recall ever seeing one under mine, either kitchen or bathroom.
All.......No
Most....Yes (very common)
They are used to keep 'P' traps on sinks from getting sucked dry when draining grey tanks.
They are downstream of sink 'P' traps on a short stub pipe.

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