After owning 3 RVs this was a fist. Last trip ready for winter, had drained tanks at park rig was level came home parked on pad which is level. Always remove termination cap and open all 3 valves to air out. about a week I smelled sewer bad. Ok closed valves drove rig up on 2 2x8sfor better drainage. I put 5 gallons water in each tank then open 1 valve at a time They all over filled the bucket and lots of bad things also. My Keystone Avalanche is two years old and have traveled about6,000 miles never completely drained looks like. So you might want to check it out. I guess the tanks are high on the drain side Thanks Keystone so now I guess its 2x8 time if I want it drained completely. Something you might check might just be a breading ground for who knows what?

Don't make dumping waste tanks complicated.Waste tanks are holding tanks. There will always be some liquid left after dumping.Fact is after dumping and flushing you should close drain valve and then add a few gallons of water back into tank so that the bottom stays wet and anything left behind doesn't dry out, stick/turn hard and STINK.

The last thing I would want to do is air out my tanks. That is like drying out all the water in your septic tank. All you have left is a bunch of hard s###.Dave

Since the tank is wide and shallow the trailer needs to be leveled by the frame, not a refrigerator shelf. Also, tanks develop a belly that retains some liquid. I think that most folks would find the same results if they checked like you did. My tank flusher leaves much behind, so I add water for my trip home and dump again into my sewer connection.

All waste tanks I have seen are tapered on the bottom towards the drain. Tanks will bulge in the middle when full as the previous poster said. A common problem is for the parking apron at the dump station to be sloped the wrong way.

Check your holding tanks | Good Sam Community

mosseater
Explorer II
Oct 12, 2015
I frequently use my Lynx blocks to raise the other side of the trailer when I dump, but I always put at least four flushes back in with my chemicals, too. Today I flushed for maybe the last time for the season, and if so, will put the remaining anti-freeze down both tanks to protect the exterior valving.
BigSur2
Explorer
Oct 13, 2015
Keep 'em wet. ALWAYS keep water in the bottom. I dump thoroughly...then add water back to the tanks for the next trip. NOT FUN LESS ITS WET!!!!! :)
pasusan
Explorer
Oct 13, 2015
We find lots of dump stations that are sloping in the wrong direction. When we pull up we check the level, and if it isn't we put a leveler block under a wheel.

We also clean off all dishes and pans with paper towels before they go in the sink.
4X4Dodger
Explorer II
Oct 13, 2015
First of all my tanks drain from the center (longitudinally) at the bottom/side. and the tank is formed so that it slopes in all directions to that point.

You should get underneath and figure out where your tank drain really is. Dont assume it's at one end of the tank and that raising one side of yout MH will empty it.

I agree with all of those that have written that this is an answer in search of a problem...you really dont have a problem. Leave it alone.

The way I handle the tanks is that I do not even hook my drain hose up at sites. I keep all the valves shut and let the tanks fill completely. Then, and only then do I dump them. This means that you always have more than enough liquid and far more pressure to dump those tanks clean.

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