dumping gray water, apparently no vent?

The grey water vent on my rig is under the kitchen sink.

Pull the black tank handle and allow it to drain. Leave it open and pull the grey tank handle. The gray water will help flush the bottom of the black tank and your grey tank will drain just fine. My 08 HR had the grey vent plumbed in to the piping not the tank and it was a little slow unless the black tank was left open.
Randy

I'll look at the trailer next time pick it up. I only remember one roof vent.

Great idea on the black water tank partial open.

This trailer is brand new to me, and I'm brand new to camping and TT, so still learning, but no stranger to plumbing.

philh wrote:
Black water dumps fine.

Gray water tank is obviously not vented. Should it be? What can I do to overcome the vacuum issue while dumping?

What you can do is leave your black water valve partially open to vent it.

Sometimes a vent pipe "stack" will drop from its proper position (height) at the rooftop. If it drops enough to submerge the tank end into the tank contents (liquid) it is no longer a vent. Can you get up there and look? Would probably have to remove a vent cap/cover to see.

how long have you had the camper and did it always do that?

IF the Air Admittance Valves failed grey tank would still drain properly unless vent line is obstructed.

Reason for the AAVs is to keep 'P' traps from getting sucked dry when drain grey tank.

Grey tank vent is plugged.
Need to go up on roof, locate vent and clear the vent pipe

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.

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.

philh wrote:
Black water dumps fine.

Gray water tank is obviously not vented. Should it be? What can I do to overcome the vacuum issue while dumping?

Both your black and grey tanks should have stink pipes running up to the roof, just for the purpose of venting those tanks. Yours doesn't? :h