Bathroom odor?

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New member
Nov 21, 2006
Ok I have a question for the guru's! I have a 26' wilderness travel trailer and here lately when walking into the bathroom the odor will about knock you down.  This is my first travel trailer so im still learning however ive been doing lots of reading.  I will try to give you some details as to how it is used so you can have a better understanding.  First my girlfriend uses it fulltime while she is out on jobs.  This problem just recently started getting worse.  I have her dump the black tank first and then the gray to flush everything on the way out.  I then have her add water with the toilet to the black tank so she can add the appropriate black tank chemicals.  We have tried several types now.  I have recently told her to keep some water in the toilet bowl to try to keep fumes from coming up.  That seems to have helped but not eliminated it totally.  When the toilet lid is down it helps even more.  We do keep the tank valves closed when not dumping.  She just called me this evening telling me she thinks the gaskets are bad? Im not sure how she figured this out or thinks she figured this out but before I go trying to take out a toilet and repair it I just wanted to ask the experienced.  Any help would greatly be appreciated.

Thank You,


Gary RV_Wizard

Site Team
Feb 2, 2005
West Palm Beach, FL
One likely cause is a lack of water in the overflow p-trap. It's probably a Thetford brand toilet and they usually have a slot opening under the rim which is intended to let water escape through the drain rather than overflowing onto the floor. The drain hose is supposed to have a low spot (just a dip in the routing of the hose) that holds water, forming a P-trap that block tand odors from coming out through the overflow hole. If that water dries up, no more blocking effect. And sometimes the installer doesn't leave enough slack in the overflow hose to form the trap. First, try pouring some water (a few ounces will do) into the overflow opening to replenish the water in the trap. That will likely solve the problem. If not, get some plumber's putty and make a plug for the overflow. If that solves the odor problem, consider taking the toilet apart and correcting the lack of a p-trap in the overflow line. However, an overflow in a Thetford toilet is a very rare problem and many folks simply leave the overflow hole blocked up.

If the smell is more like rotten eggs than sewer, you may have gray tank fumes coming back though the sink OR you may have a bacteria in your hot water tank that generates a strong sulphur-like odor. If that sounds (smells?) like your problem, ask further and we can help with that too.

Hope this helps.


Well-known member
Oct 15, 2006
Also check your vent tubes that run from your holding tank to the roof.  On a trailer I used to own a while back, the pvc vent tube had a loose coupling, allowing air to vent in the trailer.


Dec 15, 2005
We live in ours full time.  It's been parked now since May in the same spot.  Our bathroom has NO oder problems since June.  Before that the funk out of the bathroom would knock you down, especially when you flushed it.  I tried several chemicals and sure fired solutions.  I even installed a fan on the roof vent to pressurize the bathroom to force the funk out.  No luck.  Then a guy told me what to do, and it works great.  Go to the dollar store and buy some $1 dish washing soap and a jug of scented bleach.  Empty the tank and dump a whole bottle of dish soap and about a pint of bleach in the tank and fill it 2/3 or so full of water.  Let it set overnight using it as normal.  The smell should now be gone, if it's not repeat, the soap needs to loosen the oils in the waste that are making the odor and holding the poop as solids, well actually bacteria make the odor, but you get the idea.  Drain it in the morning and shut it off and add 1/2 bottle of dishsoap and flush it down with a bit of water. Now always use it until it's a least 1/2 full before draining, if it starts smelling between dumps add some more soap.  Use plenty of water each flush, even for yellow water.  We flush ours at least 3 seconds.  Use only quilted Northern paper as it is the best IMHO.  With the wife and I we dump our twice a week always adding more soap. NOTE this is only for a parked rigs because the soap will bubble up in transport.  So when traveling drain and use the proper chemicals.  Fred


Jan 9, 2006
We had a smell problem with our 2006 Jayco Jayflite.  I tried different chemicals, then bought a Flush King backflusher.  That helped some.  Then I finally bought the hose attachment that has the spinning water jet on the end.  I use that to get a really good flush and leave the tank clean.  My wife ( who can smell onions two weeks before I eat them ) sonetimes notices a smell so I'm going to check out the p-trap  too !!



Moderator Emeritus
Jan 29, 2005
Home is where we park it
IMHO the biggest cause of excessive black water tank odors it the use of chemicals that kill the bacteria.  Use of any chemicals that contain formaldehyde is not good.  Formaldehyde is one of the best preservatives known.  Now why would anybody want to add something that will preserve the contents of their black water tank? ??? ??? ???  Once Formaldehyde or chlorine has been introduced into the BWT it can take several uses without it to repair the damage.

Several of the members here have learned that NO chemicals are necessary.  Let nature do its thing.  If you feel you must add something then only enzyme type products such as Pure Power.  It has been a very long time since we have used anthing in the BWT.

Things that can make odor inside the coach are: plugged vent pipe, dry p traps in the sinks or shower.  Odor from the gray Water can be just as bad or worse than from the BWT. 
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