Odor on the road

[snags1962]

When I start to head down the road the black tank fumes permeate the cab and coach. The tank is not full but the gauge lights as full.
Lexington 2008 255gts. Help

[timfromma]

Do you use tank chemicals?

How's the seal on the toilet valve?

Do you rinse your tank when you dump?

[Teaman]

Teaman here. - Newbe on forum, just bought 2013 Sunseeker 2300 and delivered in August. Noticed odor problem after first use. Have been looking for answers on forum too. I am suspicious of poor design and or installation of holding tanks vent pipes. I still need to get on roof, pull off caps and try to measure gap from pipe to bottom of tank.

I found I could only use Gray water tank for three days before odors would invade coach/rig (about 1/3 full). That indicates a 'dropped' down vent pipe into the tank. Nearly confirmed after I started leaving graywater drain open to the park sewer line. No more sudden surges of odor into coach rig. Blackwater tank not as bad. I think that vent pipe is installed correctly.

Also possible, unlevel setup or travel motion could slosh the drain traps clear of trapwater. Especially the trap under the shower or bathtub. This would allow gases from the waste tanks to back up thru the traps and enter the coach/rig. I have found that running some water into the sinks and shower after travel can refil the traps and stop the odors. Note: this did not work on my new rig's odor problem. So I suspect a dropped pipe.

I have owned several TTs over the years, nearly every one had or developed waste tank odor problems. most turned out to be improperly installed vent pipes. So I was very surprised to find this 'preventable' problem still existed in 2013 motorhomes. At least 20 years these things have been happening. ???

[ToniandSal]

We keep the grey and black valves closed when hooked up, then open once a day to drain, then close again. No more odors coming up from the grey tank through the sink.

[timfromma]

Originally Posted by ToniandSal

We keep the grey and black valves closed when hooked up, then open once a day to drain, then close again. No more odors coming up from the grey tank through the sink.

If you put a dip in your sewer line it will work like a trap and you can keep your grey valve open.

[ToniandSal]

I have no idea what that means, but I will look it up! Thank you!

[Teaman]

Teaman here. ............. Another idea for original poster to try. Sounds like the sink or drain traps are sloshing open during travel. I have had that happen on rigs I have owned before. I found a solution for that by buying several of those flat rubber drain stoppers for kitchen sinks (about 3 to 4 inches in diameter). Place those flat rubber stoppers over the sink and tub/shower drains while traveling. Weight them down with something heavy if required.

Seems some RV sink and tub/shower drains have very shallow traps and it is too easy to slosh water out of them during travel motion. A dry sink trap allows odors to enter the coach/rig.

[snags1962]

Great ideas to try. Has anyone tried the "Cyclone" vent pipe cover? Thanks again

[Flybob]

If you have a vent open, it will create a vacuum in the unit and if there is a defective seal or vent, it will suck in bad air. Another possibility is that your black tank roof vent is near an open vent drawing in fumes. Try driving will vents closed and see if that helps. Make sure all your drain traps have water in them.

[Hoffwmn]

We had the same problem with our Leprechaun 220QB. We had the Cyclone Sewer vent topper installed and the problem was solved. Well worth the cost.

[ben31]

To find the cause, you'll need to crawl around and sniff. I know, not real fun, but it will let you know from where the smells are emanating. We had a toilet with a bad seal on the backside of it. It took almost two days to finally figure that out, and that was only by crawling around and sniffing. I called Thetford and they walked me through some things, gave me an incident number, and said to take ti to the dealer to be replaced.

I also installed the 360 siphon vent caps and I now have absolutely no smells coming into the camper from anywhere, even when I leave the vent open in the bathroom while flushing.

[Cypressloser]

Not the most likely culprit according to your description but still a possibility is the seal between the toilet bowl and the pedestal - not the valve in the bowl. It's an easy fix but not very pleasant as you can imagine.

[HerveVR]

We also had this issue with our 2012 Lexington265DS 4 years ago.

Like Hoffwmn did on his Leprechaun, I replaced the vent cap with the Cyclone cap; problem fixed.

I would believe that ben31 solution, using the static 360° siphon vent cap is also a good solution.

In both cases, air passing by is dragging bad odors out.