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Cleaning RV Holding Tank Sensors

How to clean, restore, and fix misreading or dirty sensors and level gauges in you RV black water holding tank and toilet sewerIt's a common tale, you dump your black tank and as soon as you're done you go back into your RV only to find that the tank levels are still reading "FULL". If this hasn't happened to you, it's only a matter of time before it does. It's very common to find your Black Water holding tank sensors reading "FULL" (or partially full) all the time.

Before you start beating yourself up for not properly maintaining your waste water systems, you should know that this is a very common problem that most RV users encounter from time to time. Thankfully, fixing this problem can be very simple and inexpensive.

Let's start by understanding what is causing your sensors to misread, then we'll talk about solutions to this problem.


We have written a blog post where we discuss cleaning black water holding tank sensors, in more detail. We go into depth with the different methods of cleaning your sensors: Bacteria/Enzyme Cleaners, Chemical Cleaners, and even Drain Openers for especially tough cases. We highly recommend you read it after you have read this page.

There are two primary reasons why your holding tank sensors are reading "Full"

  1. The sensor probes inside your tank have debris or waste on them that is causing them to report that your tank is full all of the time
  2. Your sensors are broken or malfunctioning and need to be replaced

If you've successfully attempted to clean your sensors and they still continue to read "FULL" then you can probably assume that either the sensors are too dirty to restore or that they are broken and will need to be replaced.


How do you clean your holding tank sensors?

There are three primary ways to clean and restore misreading sensors. We cover them in detail here.

On this page we discuss the method of using a good bacterial-enzymatic cleaner to digest the debris that is coating your sensors and causing them to misread.

To clean your sensors using bacteria or enzyme-based cleaners you'll need to start with a high-quality cleaning product that will effectively break down the grease, solid waste, and toilet paper that is resting on your sensor probes.

There are several cleaning products available that claim to clean sensors, but if you do your research, you'll see that the strongest product with the best track record of successfully restoring sensors is Unique Camping + Marine's Sensor Cleaner. This eco-friendly cleaner is specifically designed to remove the debris coating your sensor probes. Why is it better? Simply put, it's MUCH stronger than any of the competitor products and uses a proprietary blend of bacteria and enzymes to target the specific type of waste that causes sensors to misread.

Which product you use is ultimately your decision, but understand that not all sensor cleaners are created equal - so you may be handicapping yourself from the get-go if you don't start with a high quality cleaner.

One last thing before we get into this... Cleaning your sensors with a bacteria-enzyme cleaner is relatively easy, but before we go over the steps you'll follow, you need to understand that no cleaner - no matter how strong it is - can repair broken sensor probes. This is important because a handful of people will follow the steps below and still have misreading sensors. It's very possible your sensors are unfixable. However, before you assume that, please read this blog post and consider some alternative cleaning techniques before you go out and spend your hard-earned money on replacement sensor probes.

Cleaning Your Tank Sensors

Here are the steps you'll need to follow to get your sensors back on track if you are using Unique Sensor Cleaner:

  1. Close your black water valve and fill your holding tank with enough water to reach the misreading sensor. (If the water isn’t high enough to reach the sensor probe, Sensor Cleaner will not be able to clean it.)
  2. Shake Sensor Cleaner well then pour 16 oz. (half of the bottle) down your toilet.
  3. Allow Sensor Cleaner enough time to work. For Sensor Cleaner to break down the waste that is resting on your sensor probes it takes several hours to fully work. Allow a minimum of 12 hours before dumping your black water tank. It is possible that it may take up to 72 hours for Sensor Cleaner to fully clean the sensor if the amount of buildup is substantial. As a rule, give it as much time as you possibly can to ensure the deepest possible clean. It won’t hurt your tank to leave Sensor Cleaner in your tank for several days at a time.
  4. Agitation is very helpful to knock the debris loose from the sensor probes. If possible, drive the unit for several miles or rock the unit back and forth if driving isn’t an option.
  5. Dump your tank.
  6. Rinse your tank well. Leave your black water valve open and perform a tank rinse for 30 - 45 minutes to completely flush out the waste in your black water tank and to rinse away the debris that Sensor Cleaner broke up.
  7. Repeat if necessary.
  8. If, after two treatments, you are still getting misreading levels its probably time to consider replacing the sensors as they are either too dirty to restore or broken / malfunctioning. You may also consider trying an alternative cleaning method as outlined here.

If you've followed these steps you will likely find that your sensors have improved significantly (most people report that their sensors are completely restored!).

Nice work!

Don't get frustrated if it happens again down the road. As we said at the beginning, this is a very common problem that can afflict even the best of us!

If you need any further assistance, don't hesitate reaching out to us. You can always email us here. We're happy to help!

Good luck and Happy Camping!


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Important: Please note, malfunctioning sensors can be a VERY difficult problem to tackle and unfortunately, in many instances, nothing can restore them - including high pressure cleaning, the Geo Method, or dangerous caustic chemicals. Many sensors are simply beyond repair or restoration.

You might ask, "So, if there is some chance that Unique Sensor Cleaner won't work, why do you sell it?" Good and honest question! We know what a frustration it is to have sensors that don't read accurately and we know that many people are willing to try anything to get them restored - even if there isn't a 100% success rate - so we developed Unique Sensor Cleaner. Will it work every time? Unfortunately, no because some sensor probes are simply broken or beyond repair. But rest assured that Unique Sensor Cleaner is the strongest cleaner available to clean your sensors - so if they CAN BE cleaned with a high-quality bacterial cleaner, Sensor Cleaner will be the product that gets the job done.

We hope you have fantastic results in restoring your sensors, but again, please understand that our cleaner will only be effective for those users whose probes can be cleaned are aren't broken. Unfortunately, that is the simple truth. Is it worth giving it a try? We believe so, but you may disagree, hence our desire to be transparent and honest.