Originally Posted by rockport
Any plumbers out there care to explain how the air admittance valve works, should it be tightened down, why is it needed ??
Not a plumber, but in your house you have a vent stack (pipe) that goes up through the roof to allow air into the sewer pipes when you flush the toilet or use the sink.
This allows water in the P-trap to stay there and not be sucked out by the vacuum created when another sink or toilet is sending water into the sewer. Without a way for air to get in, the pipes will try to get it from what ever is easiest and it will suck water out of the closest trap to get it.
In the camper there is only one gray water vent (normally), so they install a rubber sealed check valve that prevents water from coming out of the valve, but when there is a suction on the sink, lets air (easier to move than water) into the pipes.
When not in use, the rubber seal keeps putrid gases from the gray water tank from leaking into the camper. If the seal gets hard (heat is the usual suspect), it will not close properly and allow those smells into the camper.
Replacing the valve is easy as the just unscrew; put Teflon tape on the new one and screw it right in.
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