As an Amazon Associate, Unique Camping + Marine earns from qualifying purchases.

Key Points:

• Food grease, soap scum, and other gray water waste  can cake onto the sensors causing the level monitor to read full when it’s actually low or even empty.
• To fix misreading gray sensors, follow the step-by-step instructions in our guide on How to Clean and Restore RV Holding Tank Sensors.
• If multiple treatments using Dawn Ultra dish soap do not restore your sensors, they may just be broken and need to be replaced.

We hear from hundreds of RVers who have issues with misreading sensor gauges, so don’t feel alone in this fight because it’s very common. Avoiding these issues in the future and fixing current problems are easy, even if you are a full-timer who needs to use their gray tanks while cleaning sensors. In this article, we’ll briefly describe why gray sensors may be misreading and provide some resources on how to easily restore them to proper functionality. 

Why Are Your Tank Sensors Malfunctioning?

Sensors malfunction for only two reasons:

1. Something is covering the sensor If something is covering the sensor three quarters of the way to the top of the tank (even a thin film of grease), the monitor will always read three quarters full even right after you have dumped.
2. Sensors are broken If your sensors are simply broken, it could read full, empty or anything in between; it may not show any readings at all.

Several different things can cover the gray water sensors.

• Grease and oil
• Soap scum, lotions, shampoos/conditioners
• Food debris

As many seasoned RVers know, it’s important to control what goes into your gray tank in order to avoid sensor issues, and to accomplish this, many people wipe their dishware before washing to prevent as much grease and food debris from going down the drain as possible. Because it’s very hard to stop all food debris from going down the drain, some also place a strainer in the drain to catch any rogue pieces of food that survive the paper towel wipe.

A small amount of grease will still make it into the gray tank, which means that boondockers/dry campers who have to keep the gray valve closed have some amount of grease floating on the water’s surface. This grease can cling onto the sensors as the water level rises with use or falls during dumping. Campers on sewer hook-up can keep their gray valve open, which means grease clinging to higher sensors will not be an issue, but it’s still important to control what goes into your gray tank. For a deeper dive into what you should and should not allow in your holding tanks, refer to our guide on What to Allow in Your RV Holding Tanks.

Removing this layer of grease, soap scum or other mixture from your gray tank sensors is as easy as buying the right kind of dish soap. In the next section, we will give you the resources you need to clean the gray sensors and get them working the way they should. If you want more information on how the sensors work and the pros and cons of popular cleaning techniques/products, refer to the Why Are My RV Sensors Not Working guide.

Restoring Your Gray Tank Sensors

Unlike black tanks, gray tank sensors are actually pretty painless and inexpensive to restore, even for full-time RVers. The waste that gets stuck to black tank sensors requires a strong bacteria and enzyme treatment to remove, but gray tanks only need a good grease-cutting dish soap, and our favorite is Dawn Ultra. The best part of using this soap to clean your gray sensors is that it won’t harm any bacteria in your gray tank if you happen to be treating it with a bacteria and enzyme holding tank treatment. For step-by-step instructions on how to clean your gray water sensors, refer to our guide on How to Clean and Restore RV Holding Tank Sensors.

Preventing Gray Tank Sensor Issues

Now that you've restored your gray tank sensor probes, it's always wise to avoid sensor problems in the future, and The Unique Method is the best way to do that. Since dry campers/boondockers are more susceptible to gray water sensor issues, we recommend using our Dry Camper Pack that will help you avoid sensor problems when you have to keep your gray valve closed. This pack comes with all of the treatments necessary to keep your tanks clog and odor-free and includes a helpful guide on treating your tanks while boondocking.