My son's 2001 CC Allure has a persistent gray tank odor that permeates the coach interior within a few minutes of each departure. We have tried rinsing/washing/flooding/etc., the sink traps, washing machine trap/standpipe, shower trap and the black & gray holding tanks numerous times and are pretty sure that most, if not all debris, has been purged and all of the traps hold water. Yet the odor persists....The plumbing on this coach looks in real good shape and probably rivals that found in an upscale home. There are four roof vents and we can detect the scent of bleach [which we used to identify which holding tank was causing the odor]in all of them. This would lead me to think there is a crossover vent between the black & gray tanks especially since we only put bleach into the gray tank. From what we can reach and/or inspect there appears to be no loose, cracked or broken pipes in the drain/vent system. There are also no [water] leaks under the MH either.Any suggestions from our audience?

I got these 'tablet' deodorant things that you dissolve in the sink that goes to the grey tank. I put one of these down the drain after I dump.By the next time I need to dump with a full grey tank, it's not near as foul smelling as it was before...The first time I treated my tank this way, I filled the tank with about 10 gallons of water (30 gallon tank) before I left home. The guy at the RV store where I got the deodorizer suggested this to kinda 'stir up' the tank and it'll get rid of the crud build up on the walls of the tank and whatnot..That was a couple of years ago and my grey tank does not smell as bad as it did before, and the tank sensors actually work better too! :)Good luck!Mitch

Look under bathroom sink and/or kitchen sink areas for an Air Admittance Valve.They are installed on a stub pipe just after the sink 'P' traps.They allow air to be pulled into drain pipe when dumping so that vacuum is not created in drain pipe and suck the water out of 'P' traps.If they stay open, smells from grey tank will come back into inside of rig.New ones (inexpensive) can be purchased at most any hardware store.They just screw onto end of stub pipe.

Exactly! Find, remove, and replace the AAV. Adding chemicals to "mask" the odor does nothing to fix the problem, it only puts a temporary bandaid that will need to be replaced.....money down the drain (no pun intended).Ron

May also want to give Cyclone Vents a try.Cyclone Sewer Vents

Old Biscuit has the correct fix.

Holding tank odor... | Good Sam Community

MitchF150
Explorer III
Jul 12, 2013
I got these 'tablet' deodorant things that you dissolve in the sink that goes to the grey tank. I put one of these down the drain after I dump.

By the next time I need to dump with a full grey tank, it's not near as foul smelling as it was before...

The first time I treated my tank this way, I filled the tank with about 10 gallons of water (30 gallon tank) before I left home. The guy at the RV store where I got the deodorizer suggested this to kinda 'stir up' the tank and it'll get rid of the crud build up on the walls of the tank and whatnot..

That was a couple of years ago and my grey tank does not smell as bad as it did before, and the tank sensors actually work better too! :)

Good luck!

Mitch
Old-Biscuit
Explorer III
Jul 12, 2013
Look under bathroom sink and/or kitchen sink areas for an Air Admittance Valve.

They are installed on a stub pipe just after the sink 'P' traps.
They allow air to be pulled into drain pipe when dumping so that vacuum is not created in drain pipe and suck the water out of 'P' traps.

If they stay open, smells from grey tank will come back into inside of rig.
New ones (inexpensive) can be purchased at most any hardware store.
They just screw onto end of stub pipe.
lanerd
Explorer II
Jul 12, 2013
Exactly! Find, remove, and replace the AAV. Adding chemicals to "mask" the odor does nothing to fix the problem, it only puts a temporary bandaid that will need to be replaced.....money down the drain (no pun intended).

Ron
FrankoToo
Explorer II
Jul 12, 2013
May also want to give Cyclone Vents a try.

Cyclone Sewer Vents
imgoin4it
Explorer
Jul 13, 2013
Old Biscuit has the correct fix.
MitchF150
Explorer III
Jul 13, 2013
Oh... I don't have the bad smell IN the rig.. It was just when dumping.. The grey tank smelled worse than the black tank...

If it's INSIDE the rig that smells... (don't know why I missed that part) it's what the guys said above more than likely..

Good luck!

Mitch
kennethwooster
Explorer
Jul 13, 2013
Ive had problems with oder. A deaker gave me unique rv digest. It definitely cleaned my black tank, so would do same for gray. It is advertised for gray as well as black. I also agree it could be the valve mentioned above.
Ron3rd
Explorer III
Jul 13, 2013
Old-Biscuit wrote:
Look under bathroom sink and/or kitchen sink areas for an Air Admittance Valve.

They are installed on a stub pipe just after the sink 'P' traps.
They allow air to be pulled into drain pipe when dumping so that vacuum is not created in drain pipe and suck the water out of 'P' traps.

If they stay open, smells from grey tank will come back into inside of rig.
New ones (inexpensive) can be purchased at most any hardware store.
They just screw onto end of stub pipe.

That would be my first move too just to rule it out as the cause. They also refer to these by the slang name "cheater vent". Any Lowes or Home Depot has them. Just replaced mine. Cheap.
studies01
Explorer
Jul 13, 2013
Thanks for your advice & suggestions. We will replace all 3 of those "leaking" AAV's with solid plugs & see if it makes any difference....
Bobbo
Explorer II
Jul 13, 2013
studies01 wrote:
Thanks for your advice & suggestions. We will replace all 3 of those "leaking" AAV's with solid plugs & see if it makes any difference....

DO NOT DO THAT!!!! What you will do is cause a vacuum in the drain line to the sink, pulling the water out of the trap. That is guaranteed to let tank odor in.

Replace the AAV with a new AAV. Do not plug it! YOU WILL BE SORRY!

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