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7 Ways to Clean Your RV Black Tank Sensors

RV black tank sensors are a quick way to tell when to empty your tank. However, they don’t always work as expected. In fact, tank sensors giving false readings is one of the most common issues within the RVing community. 

Airstream RV blank tank sensor cleaning
Photo by Tyler Casey at Unsplash

If your sensor is problematic, indicating a full or partially full tank even after you’ve completely emptied them, this guide will help you solve the problem. We will highlight a few cleaning methods for RV black tank sensors to ensure you can accurately track how full or empty your tank is.

What’s an RV Black Tank Sensor?

Black tank sensors are made up of small metal knobs mounted on the inside of the tank with small screws or fasteners. The probes are placed at different heights and are wired to the sensor panel or tank monitor. The number of knobs depends on the RV model. 

When a knob gets wet, it lights up the monitor, indicating the approximate liquid level in your tank. This lets you know whether the tank is empty, ¼ full, ½ full, ¾ full, or full. Correct sensor readings are especially important for boondockers, since you need to know exactly when to find a developed campsite to empty your tank. If you rely on guessing, you’ll soon be dealing with a messy, overflowing toilet.

Why won’t My Airstream Black Tank Sensors Correctly Display Sewer Levels?

There are a few reasons why black tank sensors may transmit false readings. Most of the time, it’s because there is debris caked on the sensors. For instance, a wet piece of toilet paper stuck to a knob can make the indicator on your tank monitor light up even after you’ve flushed the tank. Human waste can also gum up some of the sensors. Fortunately, deep cleaning black tank sensors can help correct the problem.

How to Clean Your RV Black Tank Sensors and Solve the False Readings Issue

If your black tank monitor indicates that the tank is partway full even after dumping, there are a few methods you can deploy to clean the sensors. We will start with the simplest solution to the more complex options for stubborn problems. Also, make sure you’re performing these cleaning procedures at a campground with water and sewer hookups, and that you’re wearing gloves.

Method 1: Use the Sewer Flusher Valve in Your Airstream RV

Many of the latest RVs, including Airstreams, are equipped with a sewer flusher valve. After emptying your black tank, this in-built system clears out what’s left behind from the initial dump by providing a secondary flush that cleans the tank’s interior more thoroughly using a rotating sprinkler. 

On an Airstream RV, you can find the sewer flush connection somewhere in the general vicinity of the black tank dump valve, sometimes slightly above the sewer hose connection. On other Airstreams, the sewer flush connection is next to the freshwater inlet, so be careful and read the labels to avoid hooking the wrong one.

Follow these instructions when using the sewer flusher connection.

  • First, open the black water tank valve and empty the tank. Airstream RVs have a sticker near the sewer flusher inlet that cautions you not to use the flusher before opening the black tank drain valve. Failure to open this valve can cause the sewer water to back up into the toilet, causing a stinky mess.
  • Insert a hose into the sewer flusher inlet valve and lock it in place. Hook up the other end of the hose to your freshwater source. Use a dedicated hose with a unique color, not a drinking water hose.
  • Turn the water on, and the sewer flusher will spray water inside the tank removing tissue and other stuck residue.
  • Rinse the tank until the water flowing through your sewer hose turns clear.

Method 2: Cleaning Your RV Black Tank Sensors with Dishwasher Detergent 

This is the most convenient option, as dish soap is readily available.

  • Get a dishwasher detergent designed to be used in automatic dishwashers as it doesn’t foam up and it has excellent softening agents. 
  • Fill your black tank up to the halfway point, then pour in a few cups of the dishwasher.
  • Drive the RV for half an hour, or more so the solution can swoosh around the tank, agitate the agent, and clean off your gunked-up sensors.
  • Let the solution sit overnight to break up any remaining debris, then flush and rinse the tank at a dump station.
  • Some RVers prefer cleaning the RV black tank with ice. If you opt to go this route, dump a couple of ice bags together with the detergent in the half-full tank through the toilet, then go on a short drive. They’ll bounce all around the inside of your tank, helping to loosen the muck. If you use ice cubes, empty the tank after a few hours when the ice has melted.

Method 3: Cleaning Your RV Black Tank Sensors with Hot Water

This method also doesn’t require any complex solutions or equipment, just lots of hot water.

  • Boil around five gallons of hot water, make sure the valve is closed from the outside, then dump the water in the empty black tank through the toilet.
  • Allow it to sit for an hour before emptying the holding tank. 
  • The steam from the warm water will loosen up any solids on the sensor.
  • You can also drive around or pour some powdered dish soap to make the method more effective.

Method 4: Washing Your Blank Tank Using a Sensor-specific Cleaner 

These products are specifically designed to clean blank tank interior sensors. They are often highly concentrated and powerful, capable of removing goo and toilet paper that’s clinging to your sensor probes. Instructions vary depending on the manufacturer, but here are a few tips. 

  • First, close your black tank valve, then fill your black tank with water until it covers the sensor knobs.
  • Add the recommended amount of sensor cleaner into the black tank through your toilet.
  • Drive around for 30 minutes so the agent can work the walls thoroughly. 
  • Let the cleaner sit for 12 to 72 hours, then drain the tank.
  • Rinse the holding tank a few times to get rid of all the cleaner.

Method 5: Cleaning Using a Black Tank Cleaning Wand

A black tank cleaning wand, also known as a sewer tank wash spray, is a flexible wand with an on and off valve and a sprayer that spins around at a very high speed dislodging the stubborn waste deposits on the tank’s sides. It offers the most direct way to clean your RV’s black water tank.

  • Attach the cleaning wand to the end of a garden hose and run it inside the RV to the bathroom through an open window. 
  • Put the wand’s attachment through the toilet to the black water tank, then power rinses the inside of the tank. 
  • Open the black tank valve and rinse it until the water running from it clears.
  • Always confirm the location of your black tank prior to making a wand purchase. Some RVs, like fifth wheels, may require a longer wand.

Method 6. Cleaning Your Sewer Tank Sensor Using the Rhino Blaster Tank Rinser

This is a system that securely connects to your RV’s sewer outlet and allows you to shoot water up to the black tank from the outside of your RV and flood the black tank. Here’s how to use it.

  • You’ll first need to buy this system. Make sure you get the one that has a gate valve to prevent the black tank water from flowing out before you completely flood the tank. 
  • Hook the Rhino Blaster to the septic, then attach a garden hose to it. The hose attachment has a vacuum breaker to prevent backflow into the freshwater supply.
  • Open the tap attached to the garden hose, and a blast of water will wash off any grime on the side of your tank. You can add some dishwashing detergent through the toilet.
  • When the tank is flooded, open the rinser’s gate valve to flush the tank.
  • This method doesn’t require you to drag a hose inside the RV or hold the toilet lever to get water into the black tank. Just remember to use a different hose than your potable water hose for this procedure.

Method 7: Using Chloride Bleach

Although this method is effective, you need to follow the right procedure to avoid damaging your tank. Bleach can harm the rubber gaskets and seals of the plumbing system in your black tank.

  • Fill your black tank halfway or 2/3rds with water.
  • Pour half a cup of bleach down the toilet, and drive around to let the water splash around the walls. 
  • Don’t let that solution sit in your tank for long, so empty the tank immediately after you’re done driving around. 
  • Now refill the tank with clean water and rinse all the chlorine. Repeat the rinsing to get rid of all the bleach.

I Did All That and My Airstream Tank Monitor Still Reads Full

Sometimes, inaccurate sensor readings are usually caused by a damaged sensor not caked on debris. In some RV models, the sensors are usually mounted on the exterior, so cleaning the inside may not be the solution. In such a scenario, you may need to take your RV to a certified Airstream technician to look into the matter. 

An internal sensor can also get damaged permanently due to corrosion. If it still doesn’t give correct readings after extensive cleaning, consult a technician. You may have to replace them or install electric exterior-mounted sensors. Even with an electric system, you’ll still need to wash your holding tanks regularly as the exterior sensor may misread when the inside wall around it is coated with debris.

Flush Your Black Tank Regularly to Prevent Sensor Problems

The best way to keep your RV black tank sensor functioning accurately is by emptying and flushing your tank thoroughly after every camping trip. If your RV has an inbuilt sewer flusher, always use it to rinse the tank after dumping it. This way, you’ll never have to deal with a black tank sensor not working because of sludge buildup.