RV Holding Tank Monitor Replacement

RV tank Monitor
The install is fairly straightforward and the instructions were helpful in guiding us through the install. The hardest part of the install was the decision on where we should install the control panel.

Within the first few months of living in our RV full time, we quickly learned that the current RV holding tank monitoring system was not going to be effective. The internal sensors began to foul and the readings were no longer reliable. We began looking for a solution.

The Manufacturer Installed Sensors

Most RV manufacturers install RV holding tanks with sensors molded into the side of the tank. When liquid comes into contact with the sensor it completes the circuit giving you a reading of your RV holding tank level. The typical readings are Empty, ⅓, ⅔, and Full. With our black tank we never really knew how much was actually in the tank. Our black tank would always read ⅓ after it was emptied, then would quickly read ⅔ shortly thereafter. Then it would be a guessing game for when it was time to empty the black tank. 

This is not a problem that plagues just RV black tanks it can also affect your grey and fresh tanks. There are all kinds of tips and gimmicks out there to try and clean the sensors. However, they all seemed to only be temporary solutions. 

Finding the Solution

We found two systems that use external sensors on the RV holding tank. Having external sensors on the tank would make them resistant to fouling by the contents of the tank. These two monitors would not  require the installation of new holding tanks. The sensors they use read through the side of plastic RV holding tanks. The SeeLeveL by Garnet and the iSeries by Tech-Edge. Either system would provide the solution to our issue.  

SeeLeveL ii by Garnet

The SeeLeveL ii 709-4LP was the model we were considering for our RV. Since we need to monitor the black tank, two gray tanks, and the fresh tank. We also wanted the ability to monitor our LP tanks. The 709-4LP did have two drawbacks for us. It did not have the audible alarms for hi and low tank levels. It also is only capable of monitoring one LP tank.  While the SeeLeveL ii 709-4LP was capable of monitoring our 4 tanks and one of the LP tanks it did not meet all of our needs. However, they have other models that may provide a solution for you.

iSeries By Tech-Edge

The iSeries has only one model and is capable of monitoring up to six RV holding tanks and two LP tanks with 90-ohm sending units installed. The iSeries allows for programming the high and low-level alarms for each tank. In addition, the iSeries allows you to program a custom name for each tank. The iSeries has three calibration settings so it can more accurately read the levels of irregular shaped tanks. 

The iSeries is the tank monitoring system that we decided to install. With the ability to monitor 2 LP tanks and the system’s ability to calibrate irregular shaped tanks. As well as having the capability to program a high and low alarm. 

In the iSeries Package

When you open the package you will find the display/control panel, three sensors, aluminum tape, and the instruction book.  Since we needed to monitor four tanks we ordered an additional sensor available on their website. Also available on their site is the PVC rod for metallic RV holding tanks and fuel tank sensors. You can also find switches that you can install to control your water pump and water heater.

RV Tank Monitor

Tools Needed

The tools required to install the sensor are fairly basic and should be tools that you have while RVing. (Future Blog Tools Every RVer should have in their RV). A pair of lineman pliers, Wire cutters, Wire Strippers/Crimper and/or Soldering iron.  Screwdrivers and a socket set to remove the panel to access your tanks. You will also need a Dremel or Rotozip to cut the hole for the panel or you could use a keyhole/jab saw. 

Materials Needed

The materials that you will need to install the iSeries RV holding tank monitor are electrical tape, 18ga wire, and wire butt connectors


The install is fairly straightforward and the instructions were helpful in guiding us through the install. The hardest part of the install was the decision on where we should install the control panel. There are several illustrations, a chart, as well as a cutout template. Also on their website is the link to several videos to help you through the process. For us, we needed to remove all of the Coroplast underbelly to get access to the RV holding tanks. 

We also had to pull out the dishwasher since we were installing it onto the side of that cabinet. Once I figured out where the screws were hidden it slide right out. Just remember if you use the sink while it is disconnected to cap off the drain line. If you do not you will be mopping up water from under the sink.

We were able to use the two wires off the existing RV holding tank sensors and control panel. Just make sure that you are pulling the correct wires when you are rerouting them from the old panel. If not, you could spend several hours trying to figure out where the wires you accidentally pulled came from. The new sensors use three wires. By using the existing two wires it allowed us to run one new wire to each of the RV holding tanks. 

MODA sensor on the RV holding tank for fresh water

The instructions are straightforward on where, how much, and the space needed between the two strips of aluminum tape, before applying the sensor. Once you install of the sensors, run of the wires, and connect them to the control panel. Then all you will need to do is calibrate the sensors.

Find Our Tank Capacity

The instructions are detailed on how to calibrate the sensor and to do so you will need to know the capacity of your RV holding tanks. We accomplished this by purchasing a save a drop water meter to find out how many gallons each tank holds. According to the build sheet of our fifth wheel we were supposed to have an 80 gallon fresh tank and three 40 gallon waste tanks.

What we found was that our fresh tank held over 100 gallons when starting from a completely empty tank. We then drained and refilled the tank. Doing this three times, enabled us to flush the Camco TastePURE Spring Fresh Water System Cleaner and Deodorizer from the tank. The flushing process then gave us an average of 80 gallons for the fresh tank.

The gray tank for the shower and bathroom sink held 40 gallons. The Black tank also held 40 gallons. However, the galley tank only held 36 gallons. We found that the galley tank was just a little smaller than the other two tanks. After taking measurements of the tanks we found that it is a little shorter than the other two.

Sensor Calibration

The RV’s fresh water holding tank is oblong so we followed the instructions for the 25% calibration for that tank. The Galley, Grey, and Black holding tank are more of a wedge T-shape so we used the 10% calibration on these tanks.

Once we tested each tank’s calibration we found that the iSeries worked really well. Though the real test would be how well it holds up over time. (2018 Upgrades One Year Review Coming Soon)

Don McElfresh

Don McElfresh

Marine Veteran with a background in engineering. With over 20 years experience in leadership roles in retail and news media. Started full-time RV living in March of 2018 to get back to enjoying life through hiking and photography.

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