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RNuzzolo

Sewer Smell While Traveling

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I am having problems with a sewer smell while traveling down the road. The smell goes away when I park. I've put water down the black and gray vent pipes and replaced the cover on each. I've checked that the sinks and shower traps have water in them. It does not appear the vent pipes have dropped into the tank. I recently read something about making sure the check/vent valves are working OK. Can someone tell me where they are. I do not see anything under my sinks that looks like a check valve.

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Welcome to the FMCA Forum.

Your sinks COULD be vented to the roof, or they could be vented to a check valve. Just look under the sinks.

Next step (sounds like you have already verified water in all the P traps (including shower) is to minimize the vacuum inside the coach when you drive. Driving with side or roof vents open DOES create a vacuum inside and the tanks are one place that tries to "equalize the pressure". Driving with the dash HVAC to vent (vs recirculate) also helps, as it "pressurizes" the interior.

Also, there are several brands of venturi style roof vent covers that create a vacuum in the tanks. A good idea of this problem persists.

Brett

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We did notice that the smell was much worse when a window was open or when I opened the vents on the engine system. I'll try what you suggested. I have roof vent covers on both roof vents and we have tried to keep them closed when driving. Are the venturi covers different from a regular roof vent cover? Thanks for the s\help.

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You asked about the check valve location.

They are often called air admittance valves or vacuum breakers.

They will be on a stub from the output side of a sink drain.

They are supposed to open and let some air in if a vacuum forms when you are dumping. This is to keep the water in the trap from being sucked out.

This is what one looks like. It is the upright cylinder on the upper right side of the picture behind the white tube. It can be removed by unscrewing it.

vacuumbreaker.jpg

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Guest BillAdams

You likely don't really need the vents that swing around in the wind so if your vents are too close together they also make a fixed venturi unit (found on most of the Prevost units we have seen) that accomplishes the same thing while driving. It's slightly possible that the swingy thingy might work better when parked but we have never had an issue with odors when parked. It's a simple T unit that you just point forward and it has the same kind of venturi opening. I am not sure where to find one but possibly someone like Marathon Coach in OR could tell you what they use.

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This is the one I am using HERE

It works well but on one occasion when we stopped for gas in UT, we had a 40 mph wind coming from the rear of the coach and it forced some tank air into the coach.

A rotating version would have eliminated that issue. However once in 7 years is not much of a problem.

If you get one like the above note there is an arrow molded into the side that must point forward.

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Guest BillAdams
This is the one I am using HERE

It works well but on one occasion when we stopped for gas in UT, we had a 40 mph wind coming from the rear of the coach and it forced some tank air into the coach.

A rotating version would have eliminated that issue. However once in 7 years is not much of a problem.

If you get one like the above note there is an arrow molded into the side that must point forward.

Those are the same ones that I was talking about, I just couldn't find the information on them. We have had these on our coach that we have owned since '99 and that do a very good job. Thanks for getting the link.

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Unfortunately I have been unable to get on the internet for a few days. I did find a check valve under the counter next to the sink in the bathroom. Can you tell me how I check it to see if it is operating OK?

Thank you for all your help.

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The "smell" test is the quickest.

Is the smell coming from this under-counter area?

If you temporarily wrap the top with plastic and a rubber band, does the smell stop?

Depending on how your coach maker installed it, it is likely that you can unscrew it and clean it.

Brett

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Unfortunately I have been unable to get on the internet for a few days. I did find a check valve under the counter next to the sink in the bathroom. Can you tell me how I check it to see if it is operating OK?

Thank you for all your help.

I would unscrew it and see if it seals on pressure and opens on suction.

You should be able to blow into it to check the seal under pressure.

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I finally located both check valves and they seem to be working OK. Also, the smell is not coming from the area of the check valves. I will try one of the venturi vents. Hopefully I will find one tomorrow and test it out. Thanks to all for the assistance. I would have been lost without you advice.

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In addition to the excellent above suggestions, I put a flat stopper on top of my shower drain. I am not sure if there is a "P" trap in the drain, but the flat "stopper" (just a flat heavy piece of rubber that fits the drain grid) cured my gray tank smell when traveling.

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I've installed a venturi type cover on the black water vent and it seems to have solved the problem. I bought a rotating cover due to the fact that I could not find a stationary cover. Thank you all for your help!

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I have a 2004 Coachman Rendevous.

What does a check valve look like, while driving down south on our first trip we kept getting odor and couldn't figure out why. Under my sink after the trap the plumbing goes down and another piece goes up and is open and I believe that's where my smell problem is coming from. I'm very new at this and very confused. We were nervous to even use the bathroom thinking the odor would get worse which made the trip hard since I have four children plus my wife.

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It sounds like the valve may be missing or broken. There should not be an open pipe. If the pipe has coupling on top with female thread, that is likely where the valve goes. It's considered a mechanical vent and available at Lowe's. You can cover the pipe with a baggie taped or rubber banded tight to stop the odor until you get a new.

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Just a FYI If you have a washing machine and it has not been used for an extended period the P trap in its drain may be empty. I bought a used Pace Arrow that had been sitting for almost a year. The first few months the stench drove us crazy, we thought it was from the black tank. I found the info on a old forum. All it took was one cycle of the washer and NO more smell.

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