No water only air

[Petnut]

That is fairly common with fifth wheel trailers. The waste tanks will play no part in the problems that you are experiencing. Just as a test, why not get a 5 gallon bucket full of water and then select the antifreeze suction, put that into the bucket and turn on the pump to see if it sucks up water. If it does keep supplying water that way to see if the air problems stop.

Are we safe to assume that you know that your fresh water tank is full?

Yes, it is full. I'll try the test.

 

[Petnut]

Yes, it is. I'll try the test.