Went to dump the black and grey tank. Hooked up the flush system and went at it. Sewer from black tank came out pretty fast then stopped. Does this from time to time so thought nothing of it just watched it. Have a clear plastic elbow to watch the stuff move by. Get a build up of water in the tank and it flushes it out. Well didn’t this time. First time this has happened since we went full-timing. I shut the water off once the tank showed full. Got a snake, tried it through the toilet. Could only get the snake in about 4 ft. Tried the snake up the sewer outlet. Would only go up about 6 ft and couldn’t get it any farther. There are so many bends in the piping on this trailer so thought maybe that’s the problem. Larry, the maintenance guy at Harmony said they have had that problem with RVers before. Gave us some stuff to put in the tank overnight. Said to leave it alone for 24 hours and the open the valve. Will clean it out. It didn’t. Some colored poo water came out. JoAnn had an idea. Leave the kitchen tank closed. Close the end valve. It’s located by the sewer hose. I added that later. Leave the shower, bath sink and washer machine grey tank valve open. Do a couple loads of laundry and the water from that will fill the piping and go up into the black tank. That's me in the picture saying, “It will never work!!” But she wanted to try it and to prove to her it won’t work I let her do it. After a couple loads of laundry the black tank and the wash machine grey tank both showed FULL. So opened the valve by the sewer hose and lots of water and poo came out. When done the black (poo) tank showed 1/3 full, other grey tank showed empty. Tried the flush system this time on the black tank and after about 5 minutes the black tank showed EMPTY. JoAnn was right. I was wrong. But I am sooo glad she was right and I was wrong.