STINK IN BATHROOM

Several mentioned the anti siphon valve under the sink, that is a good source for odor from the gray tank, (which can smell worse than the black). A source of odor from the black tank can be the stool, there may be a built in vent that has a trap. Fill the stool to the very top this will fill the trap if there is one.

Don

Air admittance valves can be purchased as most major home repair places like Lowe's, Menards, Home Depot. They are inexpensive. We had to replace the 3 we have.

OK then. If it were me, I would be looking at the Vent on top by taking the cap off.
Visual inspection down the tube and maybe run some water down it while making sure the dump is open so you don't flood the RV.

Of course the other suggestions about the under sink valves are good also.

that looks like it is only used when you cant vent outside....

Old MH I've had since November. Been on a trip for 8 weeks. Dumped twice in last week. 8-10 times overall. Generally on the road with longest stay at 6 days. Only been at park with sewage twice for 2 days each. Have been keeping stuff in tank, than dumping it.
Went on the roof and checked the vent tube but saw nothing weird, but didn't really know what to look for.
Seldom run the fan before or after the odor problem.
Forgot to mention that dump gauge started registering full all the time at about the same time this started. However, since I filled with water yesterday and drained, gauge seems back to normal.

The air admittance valves in question will be under each sink in your rv and can be seen at the following link. They are available at most big box stores.
http://www.lowes.com/pd_24372-143-85539K_0__?productId=1069119&Ntt=plumbing+vents&pl=1¤tURL=%2Fpl__0__s%3FNtt%3Dplumbing%2Bvents&facetInfo=

Do you have a black tank flush valve on your tank? If not, I would have one installed and use it regularly to help keep the tank clean. Be sure and buy a separate 25ft yard type hose to hook up for this purpose only and "not" the fresh water hose hooked to your rv.

http://www.campingworld.com/shopping/item/no-fuss-flush/3495

Gene&Ginny wrote:

oldmattb wrote:
.... I guess they are called an air admittance valve:

http://www.google.com/imgres?imgurl=http://www.nachi.org/forum/attachments/f13/57929d1345301159-plumbing-vent-under-kitchen-sink-p11.jpg&imgrefurl=http://www.nachi.org/forum/f13/plumbing-vent-under-kitchen-sink-74263/&h=600&w=800&sz=59&tbnid=o8DyaANt6v25OM:&tbnh=89&tbnw=119&zoom=1&usg=__bwX6B8ccYKs8KbXb-M3-WP1ygTg=&docid=wbqrEtImhCk9pM&sa=X&ei=S17bUa_yN8T_ygG-7IHwBA&ved=0CGIQ9QEwEQ&dur=1580

Matt B

CLICK HERE to see this picture:

TOMMY47 wrote:
DAN--Not sure what other details I can provide.

Tommy, something like this:
1. How long have you owned the RV as you say it has been dumped 'twice'. Is that since you have owned it?
2. Is is a new RV and you have only dumped twice?
3. Have you been in one place for a while?
4. Have you been keeping the dump valve open while parked?
5. Have you checked anything, like maybe the vent tube?
6. Is the fan on in the bathroom?

Those kind of things may help people assist you with diagnosis.
Just trying to help....

Add a good glug of PineSol (maybe even the whole bottle) fill with water, drive aggressively, then let sit. PineSol is a disinfectant cleaner and works really well in the black tank. Dunno why more folks don't use it.

another trick to help a gunky tank is drop in 20 or so lbs of ice cubes into the black tank and drive.

when you get to your destination, dump. the ice sure helps it all break up. and be sure to use odor eliminator.

DAN--Not sure what other details I can provide.
Gene --I do have a setup similar to the diagram under the sink. Can't see but I can feel a movable top that seems to tighten and loosen. It was very loose and I tightened a little.
I filled with water and dumped the water alone. Seems better but will have to wait and see.