Black Tank issues

I am having an issue whith the black tank and I cannot seem to find the cause. We never have an issue with any type of odors until we start to drain the tank. While the tank drains and during the flushing process it seems that the odors do not leave they come inside the bighorn. I have checked behind the wall and see no problems. Has anyone had this issue or have any ideas as to what may be the cause?

A couple thoughts:

Get on the roof and pull the caps off all the vent pipes, they could be plugged by mud-daubers or bird nest stuff.

We are getting sewer odors brought back into the trailer through grey tanks, since we are full time, we had been leaving the grey tanks open all the time to allow showers and washing machine to run without worrying about filling the tank. For the last 2 weeks we have closed all the valves and let the tanks fill, even closed the flush king valve. we are now odor FREE. This is the first campground that has caused us this issue.

One other thing to check is the air admittance valve. Known as a Studor Valve. There should be one under the kitchen sink and one under the bathroom sink.
Their purpose is to allow air to enter the drain plumbing when you run water. This will prevent gurgling and allow a faster, smoother flow of water to the tanks. Sometimes they fail to seal correctly and allow odors to enter the coach.

Peace
Dave

cookie said:

One other thing to check is the air admittance valve. Known as a Studor Valve. There should be one under the kitchen sink and one under the bathroom sink.
Their purpose is to allow air to enter the drain plumbing when you run water. This will prevent gurgling and allow a faster, smoother flow of water to the tanks. Sometimes they fail to seal correctly and allow odors to enter the coach.

Peace
Dave

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Agree. Un screw those valves and go to ACE or some other place of your choosing and get ones that are spring loaded. The ones in our old Bighorn just had a diaphram with no spring. The spring makes sure the rubber seal seats. Probably cost less than $5 a piece.

This gets my vote as well. If you notice the smell when dumping or releasing a sink full of water down the drain, it is probably the air admittance valve.