Gray Tank Smell Issue

[Cougar25]

I have a 4 month old 2021 Cougar RDS. Only one problem to date, and I really can't figure it out.

We have two gray tanks, one for the kitchen and one for the bathroom. I typically leave the valves CLOSED, and only open to drain into the sewer connection every couple of days. Sometimes - but not always - after a day or two, a smell emanates from under the bathroom sink, the sink drain, and the shower drain that frankly would knock a buzzard off a manure wagon. I put chemicals in all 3 tanks, but it doesn't seem to stop it. And the only water in that tank is from the shower and the sink. We have to keep a stopper in the sink and put something to block the shower drain.

I would think we have a stuck vent valve, except for the fact that there is nothing going down those drains that should create this smell.

Anybody got any ideas?

Thanks in advance.

[jxnbbl]

In house plumping, traps collect water from the last use and block off the gases from the septic (in this case tanks). The vent allows air to enter the system so among other things it does not siphon out that water. Additionally I've read that some trailers share the black tank with some 'gray water source'.



I'd check if that last statement is true for your trailer and if yes, make sure there is a functioning trap on that.

[JRTJH]

It's possible that the "Studor mini-vent" is not completely tightened under one of the sinks or even missing or malfunctioning....

Look under your sinks and you'll find a "contraption" that looks like this photo. Make sure they are tightly screwed onto the plumbing stand... If they are, then cover them with a plastic bag (TEMPORARILY) to see if the odor subsides. If it does, the valves are leaking and need to be replaced. If in warranty, the dealer will/can do it. If your trailer is not in warranty, it's a "owner expense". They cost about $20 each at Lowe's or Home Depot. Take the old one with you to get the correct size.....

[travelin texans]

Some RVs are equipped with Hepvo traps (pictured) rather than conventional p traps, if the rubber sleeve gets damaged or is defective it will allow sewer smells to come in the rv.

[lcarver02]

You may want to do a high pressure, high volume flush and see what comes out. I would say a 10 gallon shot with a hose from the inside should flush what should not be there. Might have some kind of vent trouble or confusion of black and grey. I don't put any kind of food leftovers down the drain, not a good idea. Plenty of liquids and packs to put in there with about 10G of water.