Problems with sewer gas being sucked into the trailer from the AC

Hi, we have a new Elkmont. We are camping at an RV park in the heat of Southern CA. Whenever we use the AC, it seems to suck the sewer gas from the toilet roof vent into the trailer. We have cleaned the toilet tank and refrained from using it. Also, we are hooked up at an RV park and there is no sewer gas coming out of the in-ground hook up. The only thing we can do to eliminate the odor is to fill the holding tank with water so that there is no space in the tank for gas to be vented to the roof. The fundamental problem is that the roof vent is located immediately behind the AC. In houses, there is a building code to prevent this problem by requiring that air intakes be located substantially distant from such bathroom vents. Has anyone else experienced this problem? And if so, how did you fix the issue? Thanks so much.

Are you sure the AC is pulling the odor in? Most AC's for travel trailers recycle 100% of the air and do not bring any fresh air in from outside. Check that odor is not coming from inside somewhere.

Here is a comparison of vent caps that might offer some options:

Vent Cap Comparison

[Wavery]

Originally Posted by RogerR

Are you sure the AC is pulling the odor in? Most AC's for travel trailers recycle 100% of the air and do not bring any fresh air in from outside. Check that odor is not coming from inside somewhere.

This is correct. The outside unit for the A/C only intakes air into the condensing unit on the roof, then exhausts it back out again. The inside part of the A/C brings all of the air into the A/C unit from inside the camper, recirculates it and puts that same air back into the camper.

You may want to open up the inside unit and check it for mold or possible dead mouse or something.

We (the dealership that I worked for) once had a new car come from the factory with a dead possum in the A/C unit under the dash. They had to disassemble the entire dash to get it out and clean out the odor.

Is it possible that there could be a leak in the ducting that is allowing some outside air in? Just wondering as from having worked on a leaky AC I noticed that some of the ductwork was not sealed as well as it could have been. Not enough to notice when the AC was on but then again my 2720 does not have any vents atop the roof.

Toilet roof vent on the Elkmont? Didn't know that there was one. How is it routed?

I see grey water vents on the sides of the trailer ...