Check your holding tanks

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.

Moved from Technology Corner

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.

I wouldn't want to leave the caps off my drains and the valves open. Although it is probably unlikely, but I just don't want any mice crawling up into my tanks, or bug, or any other critter.

I suppose raising one side of the camper to help it drain better won't hurt anything, but you really do need to put some liquid back in when finished. As stated above, there is always some residue remaining, no matter how hard you try to clean it out. Let it dry out and, now you have concrete residue forming on the side of your tanks. That don't come off very easy.

I would never leave valves open to dry out. That also dries out the valve gaskets and shortens their life. In the summer some water is left in the tank. In the winter some RV anti-freeze is left in the tank. I do realize that some RVs have a very shallow tanks which takes a little more care in dumping. I think one thing that is most important. The more water you use when you flush the less problems you will have when you dump. I will have to admit the idiot engineer that came up with the shallow tank design probably never RV'd a day in his entire life.

Just a thank you for all your time on my post. Of course I flushed the black tank at the park did add water to the 2 grey tanks like we all do right? I just did not mention, waste of message space. I guess I have been spoiled on my other two R V s never seen this before. But finished winterizing today. I back washed each tank separately while on the 2x8s till they ran clear. I do agree , but no way getting all the crud out, well I do believe its done, But your right if I would have put the cap back on I would never known I was hauling around a bunch of waste all the time. Now I have clean tanks 1 gal anti freeze each tank and everything closed up air tight down below. Least last year the waste tanks had a gallon of anti freeze for company. Thanks again everyone for your time

I keep no less than 5 gal of water in my black tank at all times.

any rd but main rd wrote:
But your right if I would have put the cap back on I would never known I was hauling around a bunch of waste all the time.

I guess I don't really care that I'm hauling a bit of waste around, whether it's a gallon or 10. I use the toilet in the RV on occasion when it's sitting at home. When it's time to camp, if it's at 1/4 tank or less, I'll haul it to the campsite with me. If it's more, I'll drain and flush before camping because of the extra weight.