As I said previously I was out of the RV for a week. I dumped the tank the day before leaving. Filled it up that morning before leaving. It was basically a tank full or clean water.I added an Enzyme treatment I found at the local RV store. It said to use half the bottle but I went ahead and dumped the whole thing in the black tank. Left it sitting for 7 days.
Got home last night and this morning I dumped a lot of dirty water out the tank. (Clear elbow is one of the best things I have added!) As I said the tank was full of clean water. I had used it only once before I left. But what came out wasn't clean water! Very dirty and I saw a fair amount of toilet paper go down too. Obviously the enzymes did something.
The proof was when I connected the black tank flusher to the hose. I saw some more dirty water coming out and an occasional small clump of toilet paper, so I left it running. Checked on it no more than 10 minutes latter and the water coming out was clear! No big lumps of stuff and no toilet paper.
I have left it running for close to an hour before and the water was minimally cleaner than when I started. As I have said before I just gave up ever rinsing it clean and think it was in bad shape in there.
So there is no doubt in my mind that the enzymes worked. Not saying the tank is 100% clean, I don't know what is in there. But it is 100% better than it was!