Any suggestions to kill bad odor from black tank when toilet is used while underway?

[donnariley53]

Our coach is two years old and recently we have noticed a very strong odor from the black tank if the toilet is used while underway. Prior to about 6 months ago, this never happened. The tank is not full, we drain often. We are currently using Tank Techs Rx to deodorize our black and grey tanks

[mel s]

Originally Posted by donnariley53

Our coach is two years old and recently we have noticed a very strong odor from the black tank if the toilet is used while underway. Prior to about 6 months ago, this never happened. The tank is not full, we drain often. We are currently using Tank Techs Rx to deodorize our black and grey tanks

donnariley53
Keeping the windows and roof vents closed, not running a vent fan and always running the dash/heat blower, (not set to max/recirculate), when underway may be the solution.

If not try some of the suggestions that are sure to come.

Mel
'96 Safari

[tnteacherguy]

I know on my Tour the 1/2 bath sink flows into the black tank. While we drive and use our toilet after I flush I'll wash my hands for 10 seconds to add some water to the P trap so the odors smell more like soap than bad gas.
Don't know if yours is the same.

[NYBobbo]

Happy Camper in the black tank.... shark fin vents on the roof.... all mentioned above

[Mike Thomas]

Probably need to rebuild the toilet. Don't forget the seal at the floor. While you have it up, check for cracks and fittings that are no longer glued together in the piping.

If you have a clothes washer, run some water through it before you leave home, as it also has a trap that dries out.

Chased my smell for months before I got serious about rebuilding all of the seals on the toilet.

[AFChap]

No need to rebuild anything from your description. No smell normally, just when it is flushed while driving.


When driving, if you have any windows or vents open when you flush, air is drawn out of the black tank, through the coach, and out the open window or vent. The same would be true when parked if you have the bathroom ceiling vent drawing air out of the rig and you open the flush valve. If all windows and vents are closed, and especially if the ac is running, there will be no reverse vacuum sucking the air from the black tank.


We use no chemicals. Just water. No smells unless we leave the rear most ceiling vent open when driving ...it apparently brings in odors from the nearby tank vent stack.

[powderman]

No open windows or ceiling fan. Close lid before flushing. No need for chermicals in tank.

[Peter27C]

We had the same issue and fitted one of the Venturi type caps on the vent pipe. Made a big difference for a few dollars

Pete

[Easyrider]

As mentioned, I'd make sure your p traps are filled with water, the smell from your grey water tanks is just as bad as the black water tanks, and that may actually be what your are smelling. We've noticed that sometimes our p traps will drain, not sure how, maybe if turning while going up hill or down at just the right angle? Anyway we make sure the traps are filled with water.

[mtnmike]

I think AFChap covered most of the issue(s). We have had the same problem from time to time. Once negative pressure builds up in the coach, flushing the toilet opens a direct path to the black tank vent which creates air flow thru the black tank to provide balancing air up through the toilet. WHOOOOOEE.

The other thing that we have found, that in summer heat, the tank needs dumped, and, for sure flushed out, at least once per week, full or not.

We are full timers, and have owned an RV for 25 years and I'm personally not comfortable with not using chemical to break down waste and toilet paper. Since we wash the tanks out often, there is no bacteria that remains in the tank to help with that breakdown unless we introduce the same.

Here's to sweet smells and happy travels. Mike

[Ramzfan]

I would listen to Peter27C and his advice. I would also start using a toilet tank chemical that smells nice and also hides odors in your tank. I have been motorhoming for over 40 years and the best thing you can do is use the tank chemicals EACH TIME you empty your tanks and install a vent-mounted diffuser on your coach.

[ezdavie]

OK, I'm a know-it-all -- but I really don't know-it-at-all!! What exactly is a vent-mounted diffuser?

[Jim_HiTek]

There's likely a 'dome' over the plastic vent pipe on the roof for both the grey and black tanks, (and sometimes a 3rd vent for a secondary grey tank). Those domes don't really help venting while you're driving. Thing to do is go to Home Depot or similar and buy a plastic 'T' from the bathroom section.

Remove the dome and toss it, place the T in their place on the top of the vent pipe with the open ends of the T pointing fore and aft on the RV. The cost for this solution is around $8. Plus some rope caulking or Eternabond. So, $12.

OR, you could buy a couple of those fancy vent caps made for RVs for $30 each.

[mtnmike]

Originally Posted by ezdavie

OK, I'm a know-it-all -- but I really don't know-it-at-all!! What exactly is a vent-mounted diffuser?

It's a vent cap that replaces the original. Many of them pivot in the wind (weathervane) to keep the wind from pressurizing the tank and also to draw the odors away from your rig.

[sask66]

With our first motorhome I learned real quick to shut off the ceiling fan in the bathroom before flushing the toilet. As mentioned before, that pulls the odor up from the black tank into the motorhome.

[mngrant]

My suggestion would be oxyclean (sp?). Used this both on our sailboat and now ERA. No bad smell. And as others have states check the seals. There should be no odors.
My 2 cents

[RTegarini]

I solved our tank-smell issue with the 360 Siphon Plumbing Vent Cap, available in black or white, from Camping World and others. It was easy to remove the OEM cap, cut down the black pipe by just a little bit, and seal/install the new cap.

[donnariley53]

Thanks for the photo!

[Jim_HiTek]

$34 each retail for that 360 Siphon Plumbing Vent Cap? You can accomplish the same thing with a plastic 'T' from the bathroom section of Home Depot at $4 each.

[mtnmike]

Jim HiTek, How does the "T" rotate to accommodate changing wind direction?