How to Install a Sensor on an RV Holding Tank

Holding tank sensors monitor solid waste levels in recreational vehicles like the one seen here.

RV holding tanks store solid waste from the vehicles' septic systems until operators find a place to discharge the waste into an appropriate container. A tank sensor gives operators the ability to know when the tank is nearly full and the septic system unable to process any more waste. As an important component for easy RV use, replacing the tank sensor is part of routine RV maintenance, as the sensors are prone to fail after a few years.

Things You'll Need

• Replacement sensor
• Screwdriver
• Adjustable wrench

Instructions

Remove Malfunctioning Sensor

1. Lift latch on outside of RV that affords access to the septic system. Pull up on the hatch and leave it open. Note that the hatch is usually located directly under the toilet. Be sure the tank is empty before proceeding.

2. Locate the series of wires that are attached to the side of the tank. They usually are black, red and green and appear at stepped intervals.

3. Place the open end of the crescent wrench over the nut on the outside of the sensor then twist the wrench adjuster until the wrench is snug against the nut. Turn the wrench counterclockwise until the nut moves freely. Turn the nut the rest of the way by hand and remove.

4. Slip the wire off the probe then remove the nut that is seated against the tank by turning counterclockwise, same as in the previous step.

5. Grip the probe between index finger and thumb and push the probe through the rubber grommet into the tank.

Remove Tank and Install New Probes

1. Locate the latches or screws that hold the tank to the RV body and remove by flipping the latches open or turning the screws counterclockwise. If necessary, pull loose any plumbing that connects the toilet to the holding tank.

2. Grip the tank firmly with both hands and slide out of the RV's body. Set the tank down and locate the probe that you pushed in. Pull the probe out and throw it away.

3. Unpack the replacement probe and remove the two nuts by turning counterclockwise by hand.

4. Slip the threaded end of the probe through the rubber grommet and hold it in place with one hand.

5. Turn one of the new nuts over the threaded portion protruding through the tank and tighten by turning clockwise. Secure the nut by tightening with the wrench.

Replace the Tank

1. Slide the holding tank back into the RV body and secure it with the same latches or screws that were removed in step 1 of section 2. Replace any plumbing from the toilet.

2. Slip the wire over the threaded portion and hold in place with one hand.

3. Place the second nut over the threaded stem and tighten it by hand. Secure the nut by tightening it with a crescent wrench.

4. Close the access hatch on the RV body and secure it by pushing down on the latch until it clicks into place.

References

• RV Probes: How it works
• RVer's Corner: Holding tanks