How To FIX a Motorhome (RV) Holding Tank Sensor? EASY DIY

Most of us have had problems with our holding tank sensors; just like most, I have had it many times, but now I finally know how to fix it and prevent it from happening again.

There are three ways to fix a holding tank sensor; clean the tank properly, change the sensor or replace a broken cable. The main problem when you get wrong readings from your sensors is that you have grease, residue, or toilet paper on them. Most sensors need cleaning to work again.

There are different techniques for cleaning your holding tank sensors and many unique products; I always use things I can find in any supermarket or even already have in my motorhome.

Why Are My RV Tank Sensors NOT Working?

As a general rule, your grey water tank sensors don’t work because they are dirty, cooking grease, food leftovers, or residue from the shower cover the sensor; the sensor sees it as water and shows that as the water level. —the same principle with the black water tank sensor but with Toilet paper or feces.

There is also the possibility that your sensors are damaged or that a broken cable is causing your sensors not to work. However, those options are scarce; barely 10 % of the time is this the cause for your sensors not to work. Since you can get different types of readings when your sensors are damaged, it is difficult to know precisely what is causing them not to work and why I always assume that my sensors are dirty until I have ruled that out by cleaning them multiple times.

I always assume that my sensors are dirty until I have ruled that out by cleaning them multiple times.

-Motorhome king

How to Clean a GREY Water Tank Sensor?

Here is a step-by-step guide to cleaning your grey water tank sensor in 10 steps.

  1. Empty the grey water tank and close the drain valve.
  2. Fill up the grey water tank to 75%.
  3. Add about 20 ounces (0,6L) of dawn soap, machine wash detergent, or a product that efficiently removes grease.
  4. Drive to move it around in the whole tank.
  5. Wait for the detergent to work during the night
  6. Empty the grey water tank the next day.
  7. Check if the grey water tank sensor works.
  8. If the sensor does not work, repeat the process.
  9. If it still doesn’t work, try a different detergent and use hot water.
  10. If the sensor still does not work, look for broken wires or consider replacing the sensor.

* Dawn or similar soaps create a lot of foam that can come back up your pipes. For this reason, I prefer a liquid washing machine detergent that is very effective against grease but without the foamy mess.

Will Vinegar Clean Motorhome (RV) Tank Sensors?

Vinegar is not a good product for cleaning holding tank sensors since it does not dissolve grease more efficiently than other soaps and detergents. Vinegar is better to prevent odors in the grey water tank but will not clean your holding tank sensors efficiently.

Many people frequently use vinegar to clean different things, but it is not that good when cleaning holding tank sensors. On the other hand, if your sensors are working great and you usually clean your tank with something that dissolves grease better, and if you start getting some odors from your holding tank. Then You can use vinegar or a mix of vinegar and baking soda to help prevent odors.

How To Fix a Black Tank Water Sensor in Motorhome (RV)?

To fix your black tank sensors, you must clean them 90% of the time. To do so, empty your black tank, add hot water, add a strong machine wash detergent or a product designed for it, drive to move it all around, wait for products to work, empty the black tank, and repeat up to 4 times.

If your black water tank sensors are still not working, check for broken wires and then consider exchanging the sensor.

Here comes a step-by-step guide for cleaning your black water tank and its sensors:

  1. Turn on the water heater, so you have hot water for step 3.
  2. Empty your black water tank.
  3. Fill your black water tank with hot water.
  4. Add a lot of strong machine wash detergent or specialized products.
  5. Drive to move it around in the tank.
  6. Wait for products to work (overnight or longer if suitable).
  7. Empty the black tank.
  8. Refill the black tank with water and check if the sensors are working.
  9. If they work, empty the tank, and you are done. If not, continue with step 10.
  10. Repeat the whole process but do steps 5 and 6 for a longer amount of time.
  11. Repeat again with specialized products.
  12. If sensors still don’t work, check for broken wires to the sensors and repair them.
  13. If there are no broken wires, consider replacing the sensors.

It is a similar process of cleaning the black water tank sensors as with the grey tank sensors, except that they get dirty from different types of things. If you are lucky, it is only some toilet paper that hasn’t appropriately dissolved that is messing with your sensors, and it will just need a rinse to start working again. But, unfortunately, it can also be feces that have decided to stick around…Which is more difficult to remove.

So the black tank sensors can sometimes be more challenging to clean than the grey tank sensors; for this reason, many people use specialized products for cleaning the black tank and its sensors. I prefer to use hot water and much machine-wash detergent to finish the job. Maybe it takes a bit more time, but if I need to get some specialized product, I rarely get around to doing it in the end.

The ice cube trick is common; people dont use hot water; instead, they put a lot of ice cubes into their black tank with water and detergent and let the ice cubes smash against the walls when driving around to help get rid of the dirt. They then wait until the ice cubes have melted to drain the tank. I have never tried this trick because I have difficulty seeing that it would work better than hot water, but it could be worth a try.

How To Prevent Holding Tank Sensors From Stop Working?

Now you know how to clean the holding tank sensors properly and get them back to life; if you want to trust your holding tank sensors again, you should start keeping your tanks clean regularly. If you regularly clean them, you won’t need to use as much detergent or spend so much time doing it. Mostly it will be enough with a quick rinse each time you empty them and then give them a proper cleaning a few times a year.

Try not to flush down so much food leftovers or grease in the kitchen drain or hair down the shower drain. Start using a sink strainer in the kitchen and wipe off your plates before doing the dishes.

If you still have problems with your black water sensor even when you regularly rinse and clean the tank, consider using toilet paper that dissolves easier or adding products to your black tank that help to dissolve the toilet paper faster. If you look at the cheapest toilet paper in the supermarket that is thinner, those dissolve almost as well as the special toilet paper that you can buy for motorhomes or RVs.

Rikard Adamsson

Hello! My name is Rikard Adamsson; I am the creator of I live full-time in my motorhome, and right now, I am traveling through Europe the right way, without campsites; yes, wild camping and being off the grid works excellent even in a real beauty from 1996. I have done a lot of rebuilding and upgrades. I am happy to share my experiences with everything regarding motorhomes, RVs, or caravans with you here at

One thought on “How To FIX a Motorhome (RV) Holding Tank Sensor? EASY DIY

  1. I agree with your point of view, your article has given me a lot of help and benefited me a lot. Thanks. Hope you continue to write such excellent articles.

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