Black and Gray Sensors off

Hi. We began using our 24' travel trailer every weekend a couple of months ago and until the last couple of weeks our black and gray sensor seemed to register correctly. The trailer does not move around as it remains on our land all the time. I emptied the black tonight as it said 3/4 full and then the gray as it said full. There was hardly anything in the black as I expected... and the gray was full as I expected. Upon returning inside to check the gage.... they both show 3/4 full.

Is there something I need to do to clean a mechanism of some sort in both tanks? Again.... the trailer does not move from it's location if this matters.



Triple E

Senior Member
Re: Black and Gray Sensors off

These sensors can be a pain. If anything gets held up on them you will get a false reading. After each dump, take the water hose inside the camper and flush the dickens out of tanks. If you don't already have spray nozzel's installed in your tanks have it done when possible. With the spray nozzel's you don't have to drag the hose inside and do all of your flushing from outside. One rule of thumb is to wait till your tanks are 3/4 full before dumping. Always dump the black before the gray. Good luck and lets us know what happens. :)


Senior Member
Re: Black and Gray Sensors off

Black tanks are notorious for getting a piece of TP stuck up against the sensors and giving a false reading. Like Steve said, get the hose and flush the black tank from the top down. Wallyworld sells a piece of PVC pipe with a hose connection on one end and spray holes on the other. Just poke it down the toilet and rinse down the black tank walls. That should fix the black tank's erroneous reading. Not sure why your gray tank would be reading 3/4 after dumping. Shouldn't be anything in there to stick up against the sensors??? Let us know how things work out.
RE: Black and Gray Sensors off


I will try the hose today and then try and locate the sprayer at Camping World. Thanks for the tip and I will let you know if the hose works.

Re: Black and Gray Sensors off

Any ideas of what I need from Camping world? I see several different items. hydro flush, flush king, etc.