Dutch_12078 wrote:
The black and grey tanks often share a roof vent, but you could also have air admittance valves under the kitchen and/or bathroom counter tops. Those valves sometime stick closed. They usually unscrew from the pipe fairly easily, and only cost a few dollars at home improvement stores.
Those AAVs can be garbage. Replaced the KZ OEM one under our kitchen sink at under a year old because it failed. Bought a replacement at Lowes (under $3) and lo and behold, it too has failed a year later. Pffft...
There are quality ones available (Oatey & Studor) but cost around $30. I know 'cuz that's what we just paid Lowes for a good one. Had to as we are on a long camping trip and DW wanted it fixed like NOW... P You can get a Studor one like in the photo on ebay for under $16.
They fail open (I think you meant to say open?) and that lets the odor from the black tank escape into your kitchen area or bathroom. They're a common failure item. Should be 1 1/2" size. Grey tank odor is just awful - sorta like a dead cat or something rotting under the floor.
