Thor Forums

[David & Diane]

My 5th wheel is almost 2 years old. Both gray & black tank sensors have always worked perfectly. When I am parked, I keep the gray valve open & the black valve closed. The black valve stays closed until the sensor display reads 100%. Then I open the black valve and dump into the sewer stem where I am parked. My procedure may not be the best, but it works. I use 1-ply toilet tissue. 2-ply is too much paper.

When the black tank sensor reads 100%, open the black tank valve & drain.
My black tank sensor reads 0%
Pour 2 buckets of water into the toilet & let the water drain out.
Close the black tank valve
Pour 1 envelope of Thetford Campa-Clean Original dry powder into the toilet.
Pour 1 bucket of water into the toilet.
Pour 1 bucket of water into the kitchen sink (rinses out the sewer hose)
My black sensor reads 6% to 8% from bucket of water added to toilet after powder
DONE

I always follow this procedure whenever the black sensor reads 100% and also before towing. I have tried liquid chemicals instead of powder and other brands. The Thetford Campa-Clean Original dry powder just works best. Whatever you do, do not just leave the black tank valve open while you are parked and dump when you leave. At least for me, this is guaranteed to foul the tank sensors.