Help! Sewage problem....

jean3....I'm guessing the same as others and that you left the grey tank (sink and shower water) valve and the black tank (toilet tank) valve open for four months. Since the shower and sink water has no solids, it drains without issues. The black tank obviously has solids in it and it requires flush water and urine to keep it in a liquid state so that it will drain. The black tanks are designed to be kept closed until they're full and then dumped. In your situation, you would probably need to leave the valve closed and dump once a week if you're living in it full time.

You now have four months of solid debris that will take some work to remove. Many trailers dump from the toilet bowl straight down into the sewer tank. You need to check and see if yours drains directly into the tank. You'll probably need to look with a flashlight. If it does, find a local RV shop or you can even order it online and buy a toilet cleaning wand. It's just a 3' pvc pipe that attaches to a garden hose and has a sprayer on one end. The tool is used to stick down though the toilet bowl opening and then spray around inside your tank to clean a tank with normal debris. In your case, it can be stuck down in the tank and used to flood and slowly break up the debris.

If your tank has an angle to the drain, I would suggest shoving a garden hose down the toilet and hopefully into the tank. Since it's a hose you probably won't want to use again, cut the male end off so it doesn't get hung up going in or during removal. You can use it like a snake and then start flooding the tank with water. This will probably take two people to do or have a shut off on the hose so you can shut it off if the tank starts to overfill. I would leave the black tank valve open so as you do your work, the water and debris will drain. This may take a few days of flooding and soaking to get everything out.

Good Luck

PS...Buy gloves!

Have you had the black tank lever "open" all the 4 months? If so, you will have to clean out the tank manually, and chemicals, etc, are not going to do it. Water (and a LOT of it) to try to wash down and dissolve what is in the tank. Never open the drain valves until the tank is nearly full so that the liquids in the tank can carry out the solids. Good luck, you have a big, nasty chore ahead of you.

Chemicals probably will not work. I would try a snake down the toilet, but be gentle.....At least to create a channel to the sewer line.

Then use lots of water to rinse the holding tank. Perhaps a RV sewer wand.

Sewer wand

Opps. You have the dreaded Poop Pyramid.

This is 4 months late but don't open the black water valve until the tank is full. If you leave the valve open the liquids trickle out and leave the solids in the tank. It will take some doing now to get it all flushed out.