Black water

Does anybody have any good tricks on completely cleaning out a black water tank? I have filled it up with water many times, added the treatment, drove it around to break things up, and still my tank reads 3/4 full after draining. If I hold the flusher down and push a stick down into the tank, it looks as if it is nearly empty. Do I have a bad black water guage? The camper is new and has only been used 5 times. Thanks!


Senior Member
Black water

Yes, those guages are made bad :) I've heard that if you fill the tank part way with water and crushed ice and drive around, that cleans the sensors pretty good. Or there is at least one company which makes an EXTERNAL sensor system. This would solve your problem for good, but probably would cost in the $100-200 range.
Black water

The ice cube trick works, I've also used the bacteria/enzyme type tank chemical which cleans the sensors, fill the tank with water and adequate chemical and let it sit for as long as you can ( a week if possible, less will work ) and then dump. Roebic makes one brand (, used to use Crestline but it is no longer available.
Black water

We just purchased a 2001 Cougar which was in excellent cond. except...the prev. owners didn't use chemicals faithfully. :dead: The fellow who got our unit ready for us to pick up had already treated the BW tank and told us we could get the reg. rv tank cleaners or just pour 1/2 gal. of ordinary bleach into the stool & let it go on into the tank,leaving it for some time and that it could clean the sensors as well as get rid of the odor. Like was posted earlier though, by what I've read, these things are just "made bad". Of all things though, this really needs to be accurate!
Black water

The only way I got my guage to read accurately was to make a wand out of 1/2" pvc pipe, about 2 feet long. I put a hose connector on 1 end and a cap on the other. After drilling small holes in the cap, so the water sprayed to the sides, I inserted it down the toilet drain and turned on the water. I sprayed around until the tank was about half full then drove it to the dump station and dumped.

I now do this at least once a year or when it starts reading wrong. Cheap and works for me.