Black tank smell in coach

Bikeboy57 wrote:
Doug,

You always give good and experienced commentary, but in this one case I have to respectfully disagree with you. In my own coach, we would experience black tank odors in the coach if the potty were flushed while driving. I stopped up and blocked all the air admittance valves, and then on to blocking all vent fans. Still we would get the smell from time to time. It did seem to be related to windy conditions. A little more research and design understanding on my part showed that flushing the potty left an open path to the waste tank. If the pressure inside the coach was less than waste tank, then the odor would migrate into the coach.

I spent the 50 bucks to install two of the wind vane ventilators on the two roof vent pipes. No more smell.

You are correct. But the OP was NOT flushing the toilet in transit. I never stated that there would be NO odor if flushing in transit. There is no way that a gray tank odor could migrate thru the toilet when flushing it if EACH tank had its own separate vent pipe to the roof. Maybe possible IF they combined the 2 roof vent pipes to 1 vent on the roof. Not all RV's have a separate vent pipe for each tank on the roof. You do indeed have a natural lower pressure in the motorhome while in transit and can easily pull in outside smells. Doug