Help with black water tank, new to forum and owning a travel trailer!!

[newbie]

After messing around with the tank drains last night, I discovered I am having the same issue with all three tanks. I am pretty sure that the cables that open and close the gate valves are not tightened. Sometimes the tanks drain, sometimes they don't.

This past weekend, I opened all three tanks for twenty minutes. When I got home, grey tank two (kitchen sink) was 1/2 full. After messing with it for a while I got the valve to open and drained six 5 gallon buckets. The most disturbing part was there were maggots in the liquid from our previous trip. Since I cannot figure out how to get to the gate valves, I will have to tow it to the dealer. Bummer.

 

[newbie]

After researching the forums for a while, I learned how to access the tank valves. I opted to unscrew the corrugated plastic under belly rather than cut it. I only needed to remove about 8 screws to pull it down far enough to see all three valves. They all opened and closed fine.

I filled the three (empty) tanks with a garden hose and they all empted without a problem. One thing I discovered was when the tank was about 3/4 empty, if I closed the valve, the remaining 1/4 wouldn't drain out. I can't figure out why that would be the case.

So I will make it a habit of not emptying the tanks until they are full (on short trips I may need to add water to fill them) and see if that solves the problem.