When we bought our trailer, I'm pretty sure it was 'close' to the dreaded black pyramid. When we filled the tank with water / pee / poop and attempted to drain, it barely flowed out the discharge. I then started the following process....
After dumping I put in about 4 gallons of water down the toilet with a cup of laundry detergent. I left that in the tank for the trip home, and sitting at home, and the drive back to the next campsite.
When I arrived at the next campsite, I immediately dumped that water YUCK!!! And filled again with about 4 gallons and laundry detergent.
Use the toilet for the entire camping trip. On the last night of camping, I completely fill the black water tank with water. It sits overnight while we sleep. Next morning we pack up, drain, and repeat..... 4 gallons and laundry detergent.
Since doing this for the past few trips, We have perfect flow now and lots of solid chunks coming out. The tank level sensors are actually beginning to function.
