Upgrading the RV Holding Tank Monitor System and Review

Upgrading the unreliable factory RV Tank Monitoring system with SeeLeveL or Series by Tech-Edge. You'll learn the pros/cons of each, then our install process, along with tips and tricks. Post Updated: Product review with 3+ years of full-time RV living use!



5 min read

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

The Manufacturer Installed Sensors

Most RV manufacturers install the sensors molded into the side of the holding tank. When a liquid comes into contact with the sensor, it completes the circuit, measuring the RV holding tank level. The typical readings are Empty, ⅓, ⅔, and Full.

Like most RV owners, we could only guess how full the tanks were. Our black tank would consistently read ⅓ after being emptied, then quickly read jump to ⅔ shortly after flushing the toilet once. The guessing game stems from the design of the RV holding tank monitor system.

Not knowing the actual fulid level in the RV holding tank also plagues your grey and freshwater tanks. There are all kinds of tips and gimmicks out there to try and clean the sensors. Like many RVers, we have tried a few. However, the quick fixes are just that, only 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 faulting by the tank contents. These two tank monitoring systems would not require the installation of new holding tanks. Both use sensors to read through the side of plastic RV holding tanks. One is SeeLeveL by Garnet, and the other is iSeries by Tech-Edge. Either system would provide the solution to our issue.

SeeLeveL ii by Garnet

The SeeLeveL ii 709-4LP is the first model we were considering for our RV. It can monitor our four tanks (fresh, black, and 2 grays). However, it can only monitor 1 LP tank, and we needed 3. The 709-4LP does not have audible alarms for high and low tank levels. We found it strange, for the cost, that this tank monitor system did not have audible alerts.

While the SeeLeveL ii 709-4LP can monitor four tanks and one LP tank, it did not meet all of our needs. However, this may work for you, or check out their other models.

iSeries By Tech-Edge

The iSeries has only one tank monitoring system. That model can monitor 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 enabling a more accurate read of irregular-shaped tanks.

Because of all the iSeries system capabilities, this is the tank monitoring system we chose to install. This product allows us to calibrate and monitor our irregular-shaped holding tanks, giving us a more accurate tank reading.

In the iSeries Package

Upon opening the package, you will find the display/control panel, three sensors, aluminum tape, and the instruction book.

Additional Items

We ordered an additional sensor to monitor to complete our need of four.

Metallic RV holding or fuel tanks would require ordering PVC rods from their website.

They also have switches to install that control your water pump and water heater.

Tools Needed

The tools required to install the sensor are items you should already have for RVing:

Lineman pliers

Wire cutters

Wire Strippers/Crimper

Soldering iron

To access the tanks, you may need a screwdriver or socket set.

Depending on where you mount the tank monitor, you may need a Dremel or Rotozip to cut a hole in a cabinet. If you have a keyhole/ jab saw, it could function similarly.

Materials Needed

The materials that you will need to install the iSeries RV holding tank monitor are:

electrical tape

18ga wire

wire butt connectors


The iSeries tank monitor system came with decently helpful instructions. There are several illustrations, a chart, and a cutout template. We found that their website has several how-to videos, too. However, none of the materials could help our friendly debate regarding where to affix the tank monitor permanently.

The prep work entailed removing all of the Coroplast underbelly to gain access to the RV holding tanks. Ideally, you would be on a paved surface and utilize a car creeper. Otherwise, removing bolts under the RV is a literal pain on gravel.

We also had to pull out the dishwasher since we were installing the tank monitor onto the side of that cabinet. This straightforward task took longer than necessary as we tried to find the hidden mounting screws. Remember to cap off the drain line if you want to use the sink. Or you will be mopping up water from under the sink.

With the prep work out of the way, we evaluated the wires needed. The iSeries sensors use three wires. However, the existing original RV tank monitor system used two wires.

We used the two wires off the existing RV holding tank sensors and control panel. Doing so enabled us to run one new wire to each new RV holding tank sensor. Pulling the correct wires when rerouting from the old panel is critical. If not, you may spend several hours tracing where the accidentally pulled wires came from.

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 the sensors, run the wires, and connect them to the control panel.

Now all that is left is to calibrate the sensors.

Find Our Tank Capacity

The instructions are very detailed on how to calibrate the sensor. To begin this step, you 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.

We also pulled a copy of our RVs build sheet to expect an 80-gallon fresh tank and three 40-gallon waste tanks.

However, through the save a drop water meter, we discovered our fresh tank held over 100 gallons when starting from a 100% 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 yielded an average of 80 gallons for the fresh tank.

We continued measuring the water going into the other three tanks, all of which should hold 40 gallons. 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.

To confirm the tank is 4 gallons less, we measured it. Oddly, the galley holding tank is shorter than the other two. The save a drop water meter provided us with a more accurate calibration.

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 tanks 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 very well. Though the real test would be how well it holds up over time.

(Review Coming Soon)

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