CHECK VALVE ISSUE?

[RWjSIM2003]

I have small amounts of water under the bathroom sink checked all connections and drain pipes. could not find any leaks cleaned and dried area. next morning I see what looks like condensation on the drain pipe from the vent check valve down and bottom of cabinet is damp. Anyone had this issue? I have no sewer gas smell like the valve is bad. I am stumped

[Old-Biscuit]

Black tank flush anti-siphon valve (some are clear or brass)



Air Admittance Valve on sink drain line (can be white/different style)



Neither should be dripping.....

[RWjSIM2003]

Found the issue after sitting and watching for 30 mins I could see that the hot water line would drip every so offen and it was right above the Vent Check valve. Cleaned added Teflon tape to connector and no more leak. Life is good until the next issue !!!!

[Bill___Kate]

If it a a vent valve on the sink drain line, it is possible that the little diaphram sometimes doesn't seat properly. It is easy to unscrew it, take it out and inspect it.

If you have a built in black tank flush, there is often a check valve - vacuum breaker installed on the water inlet under the bathroom sink. These are notoriously troublesome - cheaply made, and prone to leakage. If you have one of those, it can be replaced with a similar valve, better valve, or eliminated.