Hi, to answer some questions and set the scene a bit. Yes i am permanent (goin on 5 years), full time and the only way this RV moves is side to side lol.... so driving around is not an option as spencerPJ noted.
The reason i think i have a build up is all this time it has been pretty much a 1 to 1 ratio (setting aside the short showers during the month). What i mean is that all this time when my fresh water tank is empty, my black tank is full, 1 to 1 trade off. I dont use water for anything else.
This last month i noticed all of a sudden that i still had about 30 gals (both tanks 79 gal) left in my fresh water tank but the black tank water line was showing in the toilet pipe. So that tells me there is some kind of displacement of water, a mound most likely.
I dump every 7 days like clockwork, use dropins because they have time to work in 7 days time, and always rinse my tank with 1 gal of pressured water at the end of a dump to get the bottom feeders out. I also use tons of water every flush and add extra flushes if needed. So i feel i take good care of my tanks.
I have a high pressure washer and i have a length of old hose. I was going to connect the hose to the end of the sprayer and go down the toilet or down the vent pipe to help break things up. But i wanted to try a non messy way first.
This stuff has no formaldehyde or any of those bad chemicals. I must say so far i am impressed by this stuff. I have been trying to get the black dried stuff off of the toilet collar under the flap for years now, and brush scrubbing didnt work.
Yesterday i turned off the water and opened the flap and put this stuff on that collar and then closed the flap and put some water in the toilet and waited 2 hours. When i rinsed it all that stuff was 98 percent gone and that collar was white again, alittle brushing and it was all gone.
So this bottle has 16 treatments, i way overdid it and added half the bottle into the toilet as a first treatment. By the time i dump i will be surprised if that mound is still there.. I will know soon enough. I do shake the RV several times a day to bounce the water around in there.
My sewer on my land is one of those sub grinder pumps. It grinds up the stuff and then pumps it directly into the sewer for the community. The sewer pipe is only 1 inch pipe. Even though it grinds it up i still want to help it so thats why i use the dropins and other stuff.
Thanks to everyone for the replies, i love the taco bell reply as well, too funny...