We had a 1978 821F. We sold it and now have a 1979 bunkhouse model with the rear tub/shower. There was never any noticible problem with odor in the old unit but it is very noticible in the newer unit. We've checked out plumbing and all seems good. Has anyone else had this kind of problem or have any suggestions. The previous owner mentioned something about it being an issue.

Many RVers have complained, over the years, of sewer smells in their rigs.  The biggest culprit seems to be driving with roof vents or windows open.  Those openings draw air out of a rig.  The air is then replaced by air drawn in through the roof top outlet from the black water tank, bubbled through your blackwater and released into the living area of the rig.  Solution:  don't drive with open roof vents or windows.

I'll second Brown Wheel's observation - as I had the same problem. Only happened when black water tank was "ripe", if you will, and I drove with driver's or passenger's window open. Was always worse in hot weather.
I do not drive with any of the roof vents open ever - so can't comment on that.

If my tank is empty and clean - there is no problem with driving with the window open - other than wind noise, etc.

I have a RK 21 and the odor was coming from the black water holding tank.  It was coming thru the shower drain and by adding about a cup of water to fill the trap, the odor was eliminated.  If you haven't used the shower for a while, you might try this method.  

I appreciate the information. The rest of the story is we've only used this unit a couple of times and the problem arose on the way back from a trip that was just a couple of hundred miles. driving with the windows closed and we had used shower, bathroom sink, and kitchen sink so there should have been water in all the traps. The odor was noticeable even while parked. We checked for leaks and found none. The input to the waste tanks should just be the two sink drains, shower drain, and toilet. The output should just be the dump valves and the vent that is on the roof. the previous owner had added a T to the top of the vent to try to get it to pull the sewer odor out.
The shower drains barely so we were going to try something to clear that. Other than that Everything appears to work well except for the odor. There is probably something we are overlooking and hope know a solution.
Thanks for the info

I know this is a stuped question but you do know that the toliet only goes into the black water tank and everthing else goes to the gray water tank if you have sewer smell coming from those items your in trouble check around the toilet gasket thats the only other sorse of a leak other than it coming from the vents hope this helps sometimes a very small leak around the base of the toilet can really stink up the place and if it's in to the carpet it stays there

Jim
I had not considered a leak in that area so we will check it out. Thanks for the hint.

I have driven my 1977 Clipper many miles with the cab windows open or the coach side windows cracked as my A/C doesn't work and I've never had a problems with holding tank odors.  So I'm not sold on the vacuum theory as the sole source of the odor.  First of all make sure the roof vent is not plugged with an old wasp nest, toilet paper, etc. It vents the tank while parked and underway.   Run a wire then a hose down the vent to be sure it is open.  Is the sliding dump valve in the toilet completely sealing when closed? Does it hold water indefinitely?   If it slowly leaks down, place a large glob of heavy grease around the circumference of the seal and then drive around and see if you still get an odor.  If the odor is gone, change the dump valve seal.  I really suspect your problem is in the toilet to holding tank connection.  After 25 years the flange gasket has probably dried out and lost the seal.  The lip on the tank could also be cracked.  Holding tank odors or worse yet black water could be leaking out around the flange and in the worst case soaking into the sub flooring under the toilet.  Is the odor any less after you have emptied and flushed the holding tank? I suggest you remove the toilet (2 bolts) and check that area out.  Pull up the false floor (the carpeted piece) which will expose the sub floor.  I think you will find your problem.  Please give the forum a follow up on what you find .  Bob Mollerus, ACOC 3197

Holding tank deoderant.  Thetford Aquachem is what we use.  It makes the traveling expierience more pleasant until you can dump.  I put in about a couple of ounces after dumping and add some water to the holding tank (black water tank).  

We were at Gros Vente campground between Jackson Hole and Yellowstone a few years back.  While at the dump station a fellow traveller came in to dump.  What a noxious odor.  Like the raw sewage that it was.  I can just imagine what it must have been like for others on the road following them.  Ewwwwww!

Bob
Checked seal in toilet. Poured in about 1/4 inch of water and that has held for days. Tried to find the false floor and not much luck. It has the rear bath with tub and has been recarpeted.

There is an aftermarket "T" type fitting that is available to cement onto the toilet vent above the roof. This has a venturi inside, so that the forward motion of the coach creates a slight vacuum, causing air to rise through the vent. It solved our problem. Try Camping World.

Harold, #886

EKS Bob and i were talking about the floor gasket where the toilet mounts to the floor  

Last weekend I removed my toilet in order to replace the carpet with vinyl tile. Non- removable carpet at the base of a toilet for us guys is not my idea of cleanliness.  At any rate I found several points of interest regarding possible odor problems.  The gasket between the toilet and the mounting base was cracked in multiple places although intact.  The mounting plate outlet inserts into a tubular extension from the holding tank and is sealed with a butyl caulk.  EKS indicates his carpet was replaced which required that the mounting plate be removed so it is possible that new sealant was not used or an insufficient amount used and odors could certainly leak out here.  Finally the orrignal Thetford toilet is poorly designed in that there is no formal conduit between the dump valve at the bottom of the bowel and the mounting plate opening!  The toilet contents are contained only by the huge space inside the walls of the base of the toilet. The inner side walls of the base are sprayed with sewage with each dump and unless it is frequently sprayed off well it just has to be a potential source of odor.  I've always rinsed this area off well when I dump the tank but even with that the plastic on the inner surface of my toilet has lots of old ominous stains.  As a result I'm replacing it with a Sea-Land toilet that has a solid PVC tube between the dump valve and the mounting plate, eliminating this potential problem.  So those of you with holding tank odors may want to look into these areas too.

The Bathroom sink drains into the Black tank originaly. Be sure to order all back issues
of The Clipper Journal and read them through.

Without reviewing the past issues, I remember President Bob, the Founder of the club, discussing converting his rear bath so that the bathroom sink dumped into the gray water tank.  Previously went into the black tank.  I think he said the rear baths were the only ones affected.  Rear kitchens were O.K.  You older members, please correct me if I'm wrong.  This was at a tech. session at Morgan Hill sometime in the later eighties.  I think it's written up in one of the tech. journals.  I have a rear kitchen with the black water tank dedicated to the toilet only.