RV sensors are often thought of as troublesome devices that, once they begin to misread, will never work correctly again. Fortunately this is not the case. Sensors can typically be restored to working condition with a high-quality sensor cleaner. However, if there is hard water/ mineral deposit build-up or the sensor is actually broken and you would like to replace the sensors in any of your holding tanks, it can be done. 

Supplies

Tools for removing and replacing RV holding tank sensors
Tools for removing and replacing RV holding tank sensors
  • Gloves
  • Adjustable wrench, ⅜ inch open wrench or ⅜ inch socket wrench
  • Channel lock pliers
  • Electrical Tape (any color other than black)
  • New sensor(s)

Removing the sensor(s)

RV black water holding tank sensors installed from the factory
RV black water holding tank sensors installed from the factory

Before removing any sensors, be sure that the holding tank you are removing the sensors from is completely empty. To remove the sensors for replacement, start by taking a picture of the sensors so that you can reference it for which wires go to each sensor. Typically, the wires are different colors for each sensor.

But some RVs have only one color of sensor wire, so you might want to do one sensor at a time so as to not mix up the wires. If you are removing the sensors for the black water holding tank, put on gloves first. For fresh water and gray water sensors this is left to your discretion.

Adjustable wrench on the 3/8th inch nut on an RV holding tanks sensor
Adjustable wrench on the 3/8th inch nut on an RV holding tanks sensor

Using the wrench of your choice, loosen the ⅜ inch nut that holds the wire in place.  Remove the wire ring terminal that was sandwiched between the two ⅜ inch nuts. It is a good idea to check for rust, corrosion or broken wires at this stage. If rust or corrosion is present on the surfaces of either ring terminal or the nuts, they can be cleaned with steel wool or a wire brush. If the wire is broken, then replacing the ring terminal will be required. With the wire removed from the sensor terminal begin to loosen the backing ⅜ inch nut. The nut will not need to be completely removed unless it needs to be cleaned. With the nut loosened, the sensor can be removed by pulling the backward threaded section of the sensor. Often the sensor is difficult to pull by hand so you may need to use channel lock pliers.

Cleaning the sensor(s)

Cleaning the sensors and reinstalling them is typically not a good idea.

RV holding tank sensors new versus old uninstalled sensor
RV holding tank sensors new versus old

Once a tank sensor has been installed in a holding tank and the nut has been tightened to the level required for a water tight seal, the rubber bushing expands to a degree that will require quite a lot of force to remove the sensor. When the sensor has been removed from the holding tank, the rubber bushing will maintain its expanded shape. Because of this, it will be very difficult to reinstall without damaging the sensor bushing. Because sensors are relatively inexpensive to purchase, it is recommended to replace the sensors with new ones, rather than trying to force them back into the holding tank. 

Replacing the sensors

Colored electrical tape showing RV sensor hood orientation
Colored electrical tape showing RV sensor hood orientation

When installing the new sensors, it is essential to follow the reverse of the removal steps. Start by pressing the new sensor into the holes that are in the side of the tank that you removed if from. It does not matter which sensor goes where, so no need to keep track of them. If the sensors are the stick style with a plastic hood on them it will be important to make sure that the hood is oriented in the upright position.

This is best accomplished by using electrical tape to mark the orientation of the hood on sensors before installing them. If the sensors are installed with the hood oriented down, the sensors will almost certainly collect debris and misread. Once the sensors are in the tank, begin tightening the first of the two ⅜ inch nuts. The sensors tend to twist as the nuts are tightened, so you may need to hold them in place with pliers if they are the stick style with hoods, to avoid getting them upside down. Next, place the ring terminal wiring back on the sensor. It is helpful to reference the picture you took earlier to get the correct wire on the correct sensor. Finally, connect the outside ⅜ inch nut on the sensor and tighten it down. This also has the tendency to twist the sensor so be careful that the sensor’s orientation does not change. 

Congratulations! You have successfully removed and replaced the sensors in your holding tank!

If you are interested in how holding tank sensors work, check out this article!

*SeeLevel style sensors do not typically need to be removed unless they are completely broken. If this style of sensor is misreading, the tank that they are installed on should be deep cleaned.

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