Dave Solberg

RV Waste Tanks: How to Avoid Inaccurate Monitor Readings

Dave Solberg
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Over time the walls of your RV waste tanks can get a build-up of sediments, which can falsify the sensors on the side of the tanks. Inaccurate readings caused by residue and stuck toilet paper on the walls of the RV waste tanks is a common problem owners regularly face.

Most systems have a main probe on one side and three or four several inches to the side. As the fluid level rises inside the tank, low voltage passes through to the other probes and indicates the various levels. When residue builds up on the sides of the walls, electrical continuity is still present so the probes send as if the tank is full when it is not. Even after completely dumping the RV waste tanks, you can still get a false reading from left over residue and items stuck to the walls where the probes are coming in.

If you are getting false readings, there is an inexpensive and easy way to conduct a quick cleaning of the black water tank walls. Take four to five of the five-pound ice cube bags and dump them down the toilet. The ice cubes will bang around the tank cleaning the sides and probes before they melt. Make sure to do this while driving, otherwise it will not be effective. The longer you drive the better. Once done, the water can be dumped down into a dump station.

Using ice cubes is a quick and easy way to clean residue off the side walls of your RV waste tanks. Hopefully doing this will take care of the false readings you are getting without having to spend a lot of money on replacing the probes. However, if cleaning does not work, it may be best to contact a certified mechanic.

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10 Responses to “RV Waste Tanks: How to Avoid Inaccurate Monitor Readings”

  1. Debi Ervin

    Our issue is our gray tank reading. It registers as 1/3 full even after emptying the tank. Your ice cube suggestion is great for the black, but what about the gray? We have used the Thetford gauge cleaning products several times but no improvement. Is there anther recommendation?

  2. Diana

    Not easy to dump ice in a black tank with macerator.

  3. Dean

    Another podcaster built a holding tank in his truck bed, iced it and proved that this method does not work.

  4. Susan Doyle

    I clean my waste tank every 2 weeks faithfully. My RV does not move as live in it. Probes consistently show 3/4 full even when waste water is flushed! Any suggestions??

  5. Denise Berceli

    Where can I purchase new black water tank sensors and find directions on how to replace. Thank you.

  6. Eileen Smith

    I recently purchased a small travel trailer that does NOT have any monitor for any of the holding tanks, fresh water, gray, or black water. Any suggestions or recommendations as to how to add the probes?

  7. Marlowe Jett

    My black water monitor showed full from the first day I bought it new. I should have had the dealer repair it, but thought I could. Had it since 2008, and still give full reading. Everything looks good. No loose connection and seems to be grounded.

  8. Roland Doucet

    You can also use water softener salt as it will not dissolve as fast and slosh around for a longer period of time. They are also environmentally friendly as it's just salt in a compressed format.

  9. Mike Greene

    Any idea on where to find a wiring diagram for these probes? I have a mid 2000 fleetwood wilderness that my dogs decided they liked the taste of. Can't seem to find anything online. Thanks

  10. Tom

    I guess that you don't have a "macerator toilet". Ice might not pass through too well!!!

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