We used to get the same smell coming from our closet. At first I didn't even realize the vent pipe for the holding tank was right behind the this paneling wall in the closet.
I added one of the rotating tops to the vent on the roof... the one that looks like a sharks fin... and have not had any odor problems since.
Anytime I'm up on the roof of our RV, if I'm downwind of that sucker you can definitely tell its working.
It was one of the best $25 I've spent on my motorhome so far.
My coach has grey water vent valves under the kitchen and BR sinks that can go bad. I replaced mine and got them at Lowes. Frankly, it didn't fix my problem, but others have reported that replacing them does help. Go on top of your MH and sniff the black and Grey water vents. My black water vent had no odor, but I almost fell over with the grey water tank odor. Problem solved once I got the grey tank squeeky clean. Now I flush the grey tank every time. I realize that even with a dirty tank, the odors should still not enter the coach. It could have been my washing machine P trap too?
Larry, Debbie, Tiki and Tomi
USAF Retired
2003 36' Country Coach Allure #30856
2008 Tacoma Toad
SMI Air Force One toad brake
Is there any way that you can see the tops of the grey and black water tanks? I have seen the vent pipes pull out of the tanks because they were not properly fastened in at the time they were installed. If this is the case, until you get them installed properly, nothing you do will get rid of the odor.
Badeye
"No one can guarantee success, only effort."
Bob & Fran
2005 Coachmen Sportscoach Elite 40 ft DP
2002 Dodge Durango
Ready Brute Tow Bar
Ready Brake Tow Brake
FMCA F324606
I have read on this topic for a while. Replacing all the vent caps in the coach and also installing a shark fin on the only vent on the roof. Will update on how the outcome is. Frankly the smell was overpowering. In other words "it would part your hair".
I've got a Thetford toilet also. Clay L had a suggestion that I don't know if you noticed. There is an "overflow" S trap inside the toilet mechanism. If that trap dries out, there is a direct open line from the black tank to the inside of the coach. I fill the toilet to the brim every month or so to make sure the line has water in it. This is a 1/2 inch flexible plastic line bent in an S shape and hooks to the toilet flange. It's a safety device; in the event of a leaking toilet valve. When the bowl fills, excess water will go through the plastic line and into the black tank instead of onto the floor. It's worth checking in case you haven't already.
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