Replacing Toilet Seal

It is a Thetford specific part. Easy to find on Ebay or at any RV Dealer that has a decent parts department.

Ordered mine from one of the RV Parts guys on Ebay.

Easy fix, takes less than an hour if you are handy.

As far as the smell, I drained and flushed the tank, reloaded with a couple gallons of water and a treatment of Aqua-Kem then stopped up the pipe at the flange with an old towel when I pulled the toilet.

You can do it. Just use the correct part or you won't fix the smell problem.

The rubber gasket is readily available from most RV dealers, Amazon, and I recall even seeing them in a Walmart. Many RV toilets use the same gasket.

http://www.amazon.com/Thetford-33239-Closet-Flange-Seal/dp/B000BGM7QS

Check to make sure your vacuum breaker is good underneath your sink. If the flapper inside it is dry, worn, stuck open, etc. you will also get sewer odor. Just open the cabinet under the sink and stick your nose down there. It will be evident if that's what it is.

Like others have said, replacing the rubber seal under the toilet is a simple fix but I wouldn't think a home store would have them in stock but might be worth a try.

It is an RV specific item. It is a flange seal.

It took me almost a year to track down my black tank smells to that very seal. Easy fix. Took the nut off of 2 bolts, toilet lifted off, took off old seal, put on new seal, replaced toilet, bolted down. Done.

Of course, for that year I had cleaned out vents, replaced AAVs, filled traps, etc.

You should be able to pick up a rubber toilet seal at any Home Depot, Lowes, or any large hardware store. There are several different styles that will all fit.

I would check the venting first. Are you sure you are not smelling gray water coming for the sinks , they give of a sewer smell after ages days of not dumping in warm weather. I don't really see how that seal can go bad. It is possible I guess if it was cut some how. I have had my toilet out three times over the years and have inspected the seal and it still looks good and is 20 years old.

If the toilet holds water, then you do not need a seal. Before you start on any trip on your coach fill up the traps on your sinks, kitchen and bath and run some water through the shower drain, also your washer. It will stop your smell that is venting through the traps.

I would also recommend Happy Camper to eliminate all odors even when dumping. Best thing I have ever used. Do not use the blue stuff they sell at Wal-Marts and some RV stores. That just camouflages the smell. Happy Camper dissolves the solids and turns it back into water. It is an enzyme that eats it up.

RayChez wrote:
If the toilet holds water, then you do not need a seal. Before you start on any trip on your coach fill up the traps on your sinks, kitchen and bath and run some water through the shower drain, also your washer. It will stop your smell that is venting through the traps.

I would also recommend Happy Camper to eliminate all odors even when dumping. Best thing I have ever used. Do not use the blue stuff they sell at Wal-Marts and some RV stores. That just camouflages the smell. Happy Camper dissolves the solids and turns it back into water. It is an enzyme that eats it up.

At this point I've narrowed it down enough that the seal at the toilet flange is the leading culprit. Even though the bowl holds water, I think the sewer gas is either coming through the point where the toilet meets the floor, or where the "seat" part of the toilet attaches to the base...there is a lip there that may not be air tight.

It is definitely coming from the black tank, and it definitely seemed to be coming from somewhere very close to the toilet not the drains or from under the sinks. I had leaky air admittance valves at one point and I am very familiar with the grey tank odor. This was definitely black tank odor.

zach477 wrote:

RayChez wrote:
If the toilet holds water, then you do not need a seal. Before you start on any trip on your coach fill up the traps on your sinks, kitchen and bath and run some water through the shower drain, also your washer. It will stop your smell that is venting through the traps.

I would also recommend Happy Camper to eliminate all odors even when dumping. Best thing I have ever used. Do not use the blue stuff they sell at Wal-Marts and some RV stores. That just camouflages the smell. Happy Camper dissolves the solids and turns it back into water. It is an enzyme that eats it up.

At this point I've narrowed it down enough that the seal at the toilet flange is the leading culprit. Even though the bowl holds water, I think the sewer gas is either coming through the point where the toilet meets the floor, or where the "seat" part of the toilet attaches to the base...there is a lip there that may not be air tight.

It is definitely coming from the black tank, and it definitely seemed to be coming from somewhere very close to the toilet not the drains or from under the sinks. I had leaky air admittance valves at one point and I am very familiar with the grey tank odor. This was definitely black tank odor.

Floor gasket seals the floor flange to the toilet base 'tube' (that goes from bottom of base up to bowl seal)

Black tank odors can only come up thru bowl seal (not holding water) or from around floor flange gasket

Turn off water supply, disconnect water line to toilet, remove hold down bolt nuts and lift toilet off flange.
R/R gasket
Reinstall toilet....only tighten hold down bolt nuts enough that toilet is firm/stable....no not over tighten.

Check tightness of nuts after couple days of use and for any water drips from fittings on water supply

RayChez wrote:
If the toilet holds water, then you do not need a seal.

Not true.

The flange seal on the bottom of the toilet compresses with age and and can leak, fluid and gases. I know because I had the same issue as the OP. Old gasket was completely flat compared to the new one. I removed the toilet and the platform it sits on and found where it had also leak fluid at some point as well.

Put it all back together with a new gasket and that solve my ordor issues when driving.