Water drip from overflow valve under bathroom sink

STBRetired wrote:
The only thing like that under my bathroom sink is the siphon break / backflow preventer for my black tank flush line. Or are you referring to the air admittance valve (about 1 1/2" in diameter) on the drain line?

Black waste tank flush system.....
Anti-siphon vacuum breaker backflow device
Installed at least 2' above top of tank
Flush water comes up/in bottom of valve----pressure pushes a disc up closing off the top section which is open to atmosphere.
Flush water then goes out the side and down to flush nozzle in tank

If it leaks....replace it
Black ones are CHEAP (ie: JUNK)
Better ones are available

Clear plastic and Brass ones


Junk...

The only thing like that under my bathroom sink is the siphon break / backflow preventer for my black tank flush line. Or are you referring to the air admittance valve (about 1 1/2" in diameter) on the drain line?

golf_bears wrote:
Never heard of an over flow valve on water lines. So will watch this post and hope to learn more. Never can have too much knowledge about RV. Thanks for posting.

I’m with you. Pictures would help.

Never heard of an over flow valve on water lines. So will watch this post and hope to learn more. Never can have too much knowledge about RV. Thanks for posting.