Holding Tank Usage

I dump and never come home with full or partially full black tanks. I use a flush king (you can do the same with a simple 3rd slide valve attachment), and drain the black tank completely until it stops running. Then close off the 3rd flush king valve and let the gray water back-flush into the black tank for about 10 seconds and then close off the gray tank. Now open the flush king valve again and let the black tank empty again. It pulls out a lot more "stuff". I repeat two more times, each time it pulls out more and more. I've found that the 4th time really does not benefit a whole lot as there is usually not enough left in the gray tank to help. So what little bit is left will be enough to clean out the hoses. But I empty and back flush before returning home, every trip! It costs nothing more to do this, and the assurance of having a clean black tank is "peace of mind!"