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The Definitive Guide To Cleaning RV Black Tank Sensors

January 30, 2019

How to clean and fix sensor probes in my RV black gray water holding tanks

Misreading black water holding tank sensors are notorious for being one of the most frustrating fixes within the RV community. At one point or another, you have most likely had first hand experience with this issue.

What Causes Holding Tank Sensors To Misread?

The majority of all sensor problems come from undigested waste and debris that get stuck on sensor probes, causing them to misread as full. Sensor probes are, typically, quite rudimentary and it's very easy to get false readings if you aren't using a good waste digester to keep the solids liquefied inside your holding tanks.

Unfortunately, many RV owners only consider toilet odors when they are purchasing their holding tank treatments and they don't select treatments that also effectively digest the solids inside their tanks. As a result, they are confused and frustrated when they get a clog or misreading tank sensors. 

So, the first step to ensuring your black water tank sensors remain in good operating condition is to use a high quality waste digesting tank treatment.

Broken Sensors

One thing to note before we get started, if your sensors are broken you will need to install new sensors for your RV black or gray tank. The tips and recommendations we outline below will help you clean your misreading sensors but no amount of cleaning will fix a broken sensor. That being said, we recommend you try cleaning your sensors before you replace them. It is hard to tell what exactly is going wrong with an RV sensor issue, so before you spend big bucks replacing your sensors, try cleaning them. But remember, if you can't get your sensors to work properly after you have followed the steps below, you probably have sensors that are either broken or unrepairable and you will need to replace them.

If you routinely struggle with keeping your sensor probes in good operating condition you may want consider installing sensors that are mounted on the exterior of your tank, like these SeeLevel RV Tank Sensors. Aftermarket sensors like this are a great option if you want more/better information on tank levels and are tired of hassling with OEM sensors that are giving you grief.

Major Types Of RV Sensor Cleaners

There are three major types of sensor treatments that are used to clean up and restore misreading black water tank sensors.

  1. Enzyme/Bacteria
  2. Drain Openers and Caustic Cleaners
  3. Surfactants (soaps)

We'll go through each of these types.

Bacteria and Enzyme Sensor Cleaners

Bacteria and enzyme sensor cleaners are often a very effective option for restoring your RVs holding tank sensors. These products introduce safe bacteria to your black water holding tanks that produce enzymes. These enzymes break down the waste that is coating your sensors so it is rinsed off the probes. After the enzymes have broken the waste down, the bacteria literally eat the waste, completely liquefying the solid waste. Boom, no more sensor problems. And it's totally safe for people, pets, and the environment.

Pros of Bacteria and Enzyme Sensor Cleaners
  • Usually work quickly and effectively 
  • Fairly user friendly
  • Don't always require driving, so permanently parked rigs aren't out of luck
  • Safe | Non-Toxic | Eco-Friendly
  • Usually less expensive than surfactant (soap) cleaning
Cons of Bacteria and Enzymes
  • Not all bacteria/enzyme products work well. Make sure you select one with ultra-strong bacteria strains and high quality, boosted enzymes, otherwise you simply won't see good results.
  • Often more expensive than harsh chemical cleaners

We believe, wholeheartedly, that the best RV sensor cleaner available is Unique RV Sensor Cleaner. Quite simply, it's the strongest, most advanced formula available today. Our blend of premium waste digesting microbes will work quick to get the job done and our boosted enzymes are the best of the best, so you know with 100% assurance that when you are using Unique Sensor Cleaner there is NOTHING stronger on the market!

Since we have covered bacteria/enzymes, lets talk about chemical options for treating faulty sensors.

Drain Openers and Caustic Chemicals

Another option for cleaning your sensors, which might seem extreme - but is often times recommended in RV user manuals that come from the manufacturer - are drain line cleaners, like Liquid Plumr or Drano. Caustic drain cleaners use ingredients like Lye (sodium hydroxide), Bleach (sodium hypochlorite), or Potassium Hydroxide to physically burn away the debris that is stuck on the probes. All of these ingredients (and 99% of the major brands of drain openers that contain them) are very dangerous to people, pets, and septic systems, which is a HUGE drawback. They are, however, fairly inexpensive and sometimes the ONLY thing strong enough to get the job done on EXTREMELY bad sensors - especially in Gray Tanks where grease (which is VERY tough to breakdown) is the main problem.

Pros of Drain Openers and Caustic Chemicals
  • Works quickly
  • Highly effective for burning grease that is stuck on sensors
  • Less expensive than bacteria and surfactant cleaning
  • Commonly carried everywhere
Cons of Drain Openers and Caustic Chemicals
  • Very dangerous
  • Can damage valves and seals
  • Toxic and damaging to the environment
  • Can potentially cause damage, so consult with the manufacturer of your unit before using this inside your holding tanks
  • Will kill all of the good bacteria inside your tanks so tanks must be very thoroughly rinsed before using a bacterial toilet treatment
  • Can react with other chemicals inside your holding tank and cause harm or damage

Though caustic chemicals can be a very effective solution for misreading tank sensors, you will have to decide whether it is worth the risk to use dangerous chemicals to treat your RVs holding tanks. It could result in danger to you and your family as well as the environment. It can also cause significant damage to your RV. 

It is our recommendation that you avoid this treatment process, unless you are desperate - in which case you could just safely replace your sensors with external holding tank sensors. But you don't have to take our word for it. It comes down to a matter of personal preference, taste, and what you think will work best for you and your RV.

Now, let's look into Surfactants!

Surfactants and The Geo Method

Surfactants is just a fancy way of saying soaps, and they are often used to scrub the inside of your RVs holding tanks. They are also usually combined with other products as soap isn't usually strong enough to effectively clean sensor probes. One of the common ways they are used is with a process called the Geo Method. To learn more about this method of cleaning your RV holding tanks, click here.

The Geo Method is a normally combination of Calgon and dish detergent/laundry detergent. Calgon is a water softener that makes the surfaces of your tank slick so the waste and other debris that typically get stuck on tank walls and sensors can slide off. The soap from the laundry/dish detergent penetrates waste on the walls and sensors on your holding tank and effectively cleans all the residual waste off, fixing your issue. This is a popular treatment method within the community for dealing with sensors, but may take a little time to work so be patient. 

Pros Of Surfactants and The Geo Method
  • Often works effectively 
  • Safe/Non-Hazardous 
  • Typically less expensive than chemical cleaners per treatment, but can be costly if you're buying the ingredients the first time
Cons Of Surfactants and The Geo Method
  • More effort is needed from you to help this one work
  • It isn't a perfect process so you may have to play around with it until you achieve success, which can take time
  • The Geo Method will kill the bacteria inside the tank, so if you are using a bacterial treatment you cannot use it in conjunction with the Geo Method

The Geo Method can be a bit of a science experiment and you will end up toying a lot to to get the ratios right, measuring and deciding how much you should use for a sensor cleaning.

Gray Tanks

So far, we have spoken a lot about restoring the sensors in your RV's black water tanks, but what about the gray tank? Believe it or not, restoring gray tank sensors are a completely different thing. We will be writing a definitive guide on that topic soon, so check our blog regularly so you don't miss it!


There are many options when it comes to treating your RV sensors and it can be a major pain to figure out which one works for you. Obviously, we believe that the most effective, safe, and convenient way to clean up and restore sensors is by using a good bacteria/enzyme cleaner, like Unique RV Sensor Cleaner, but ultimately the choice is yours in how you tackle this common problem.

We hope that this has helped shed some light on this tricky problem! If you have any questions that weren't covered here, email us! We'd love to hear from you!


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