grey tank stink

[deprived]

Recently the motorhome stinks whenever we run any water to the grey tank: washing dishes, showering, etc.

I couldn't figure out where the smell was coming from. I thought maybe it was coming from the p-traps or perhaps even under the floor. But it was coming from the air conditioning vents.

How on earth can running water to the grey tanks cause it to vent to the A/C duct work?

I'm very, very puzzled.

[Lynnmor]

The vent pipe that goes thru the roof may have dropped down into the tank. Check the top of the pipe on the roof to see if it is still up where it should be.

[deprived]

It’s definitely not coming from the air admittance valves. It was one of the first things I suspected but during the stink episodes, the areas under the sinks smell fine.

I’m not sure how the AC air return can be sucking gas from the vent pipe but clearly that’s what’s happening.

This ought to be fun.

[Old-Biscuit]

Air Admittance Valves under kitchen & bath sinks would really smell inside those cabinets

Stink from A/C Vents...grey tank roof vent leaking vapors into attic space which is being pulled into A/C duct work

Grey tank vent line may have slipped down below roof line which would expose attic area OR vent line is cracked
Running water stirs up grey tank contents and as water goes in air has to vent out so there is an increase in vapor flow

Tape a plastic bag over air admittance valves as a test.
A/C ON..run water down sink drains and see if you still get grey tank odors.
No odors.then AAVs are bad
Still getting odors...grey tank vent line issue

[doxiemom11]

Replace the air admittance valves under the sink. A/C circulates inside air, so if inside air stinks I guess the A/C air will stink too. Those valves under your sinks can be purchased at any store like Lowe's, Home Depot etc and are not expensive. There should be one under the bathroom and kitchen sinks.