New black tank odors

[JoeandJane]

This is our fifth season with the motorhome and until this year we?ve had good luck with smells but this year the black tank is terrible. I am draining and adding water and packets of stuff just like I always have but something seems different.  When we flush, a lot of gas comes up into the motorhome. Is there a chance that maybe the vent is plugged with bugs or something?

 

[lynnmor]

This is our fifth season with the motorhome and until this year we?ve had good luck with smells but this year the black tank is terrible. I am draining and adding water and packets of stuff just like I always have but something seems different.  When we flush, a lot of gas comes up into the motorhome. Is there a chance that maybe the vent is plugged with bugs or something?

Are you now running a vent fan?  Any fan that exhausts air will cause a negative pressure and the tank air will come up.  If you have a reversible fan, run it so that it blows in.

 

[Hammster]

Are you now running a vent fan?  Any fan that exhausts air will cause a negative pressure and the tank air will come up.  If you have a reversible fan, run it so that it blows in.

If the black tank vent line is anywhere near the bathroom vent fan there on the roof DO NOT run the fan so it blows in. You don't want to take the chance that you will push sewer gasses into the rig from the tank vent.

Be aware that the gray tank can develop some nasty odors too. You might double check the air admittance valve that is probably in the bathroom sink vanity to ensure it is ok.

Definitely could be worth climbing up onto the roof and checking the status of the vent pipe.

 

[Gary RV_Wizard]

There's a fair chance the air admittance valve in the bathroom is sticking open and that sewer gas smell is actually coming from the gray tank. The AAV is under the bathroom sink and easily replaceable, and its a standard plumbing part available wherever plumbing fixtures are sold. It just sits on top of a black plastic pipe and is usually in the cabinet under the sink.

Yes, it's possible critters have blocked your black tank vent on the roof.  You can take the vent cap off (if there is one) and run a snake down it or stick a hose in and squirt it (the black tank dump valve needs to be opened to prevent an overflow).

Are you getting gas bubble burps into the bowl when you flush the toilet? That's a sure sign that the tank isn't venting properly.