Just how full is 2/3 full? How many more showers can you take with 1/3 of a tank of fresh water? If your tank sensors are like the ones on my Rage’n, then you have absolutely no idea. You also know how frustratingly inaccurate the “Empty, 1/3, 2/3 or Full” readings are on your holding tank gauge.
A visual inspection of the placement of these “sensors” shows that they are not evenly spaced on the tanks, thus providing a reading that is arbitrary at best. On my tanks, the “Full” sensor is 2 inches from the top of my tank and the “Empty” (or 1/3) is nearly 3 inches from the bottom. I can understand some amount of over/under reading for full and empty on my tanks, but 5 inches of variance on a 9-inch tall, 150-gallon fresh water tank means that over half of its total capacity is immeasurable. So, I am left with guessing just how much of those bottom 3 inches of fresh water I really have. That’s just unacceptable when dry camping in the middle of nowhere.
Enter the SeeLeveL II™ tank monitoring system by Garnet Technologies. They have developed a proprietary external level sensing technology that provides accurate tank level information using a percentage-of-full readout. Because these sending units are mounted to the outside of the tanks, they can’t become clogged or corroded and are virtually impervious to the false readings caused by debris build-up inside the holding tanks.
The SeeLeveL system is comprised of two components: the senders and the display. Each sender is a flexible self-adhesive printed circuit board which is stuck to the side of the holding tank. The sender panel can be cut to length to match the height of the tank, and it automatically calibrates itself so that it can read from “Empty” to “Full” regardless of the height of the tank. The sender scans the water level through the tank wall using patented digital techniques programmed into the sender microprocessor. In addition to the level, the sender also transmits diagnostic information about its operation. This information can be used to determine if there is buildup of sludge on the inside of the tank, or to determine if the sender is delaminating from the side of the tank. If sludge buildup in the tank becomes extreme, the gauge will cease to operate (the tank will always read empty), so by monitoring the signal level the tank can be cleaned before the buildup gets excessive.
If the tank is more than 12 inches tall, two senders can be stacked to allow measurement of levels up to 24 inches. The display receives the information from the three sender panels via two wires (signal and ground) and displays the level information in percent-of-full on a three-digit LED display. When the front panel button for a particular tank is pressed, the display powers up and displays the level for that tank. If the button is pressed and released, the display will show the level for about 5 seconds and then shut down automatically. If another button is pressed before the display shuts down, then the new level will immediately be shown. If the same button is pressed twice, the display will hold on that tank and continue to show updated levels for 5 minutes before shutting off. This allows you to monitor the filling or draining of a tank. The display also has a button for Battery and LPG and will display the battery voltage and amount of propane you have, but only if your propane tanks have sending units built in.
Installation is relatively straightforward once you get started. It seemed that I spent more time deciding on where to mount the display than I did on the installation. I divided the project into 2 phases: the senders and the display.
THE SENDERS: First, I measured the height of my holding tanks to determine if I needed to trim the length of the sending units. My fresh tank is 9” tall and my grey/black tanks are both 11” tall, so I needed to cut the 12” sending units to size. The senders are all connected in parallel to save wiring and to simplify the installation. The senders must be programmed so the display knows which tank they are on. The senders can be programmed for either the fresh, grey, or black tank. Yes, I said programmed, but before you slip into a techno-coma, programming is done by cutting the top corners of the sender. Each sender defaults to fresh tank operation if the programming is not altered. If the sender is for the grey tank, cut the tab that says “GRY” and if the sender is for the black tank, remove the tab that says “BLK.” There is a third tab for “TOP.” This is used if your tank is taller than 12” and you will be stacking a pair of senders to act as one.
After the programming was complete, I was ready to mount the senders to the tank. The adhesive used on the senders is permanent, so relocating them is next to impossible. I decided to use duct tape on each side of the senders and stick them to their respective tanks after thoroughly cleaning the area with alcohol. This way I could easily move them if testing proved they were not placed properly for the best accuracy. Earlier, I had traced and confirmed the continuity of the wiring from the holding tanks to the OEM display in my range hood, so I was able to connect the signal wires from each of the senders to the grey tank wire from the original tank sensors. Not having to run a new wire through the floor and walls was a great relief. I grounded each sender and I was ready to mount the display.
THE DISPLAY: Mounting the control panel took a little more work than the senders. I needed to make a physical alteration to the kitchen cabinets, as I chose to flush mount the display into the end cap of the kitchen cabinet. After removing the control panel from the range hood, I located and tapped into a constant 12v source, a ground wire, and the grey tank wire that I used earlier. I ran these three wires up over the cabinets, through a loom and down to where I had used a Dremel to cut a 3x2-inch hole in the cabinet.
Next, I connected the wires to the display harness and secured the display to the cabinet with the supplied hardware. And that was it! I was now ready for...
TESTING: Immediately upon pressing the “BATT” button, the LED lit up and displayed “12.6”--so far, so good. Pressing the “FRESH, GREY and BLACK” all resulted in 0 to be displayed. I filled the fresh water tank to capacity, all the while checking the display. I watched it climb all the way until it reached “100,” and just shortly after that came the unmistakable sound of water spilling out the overflow.
I was impressed, but not as much as I would be when I tested the grey tank. For that I took 5 gallon buckets full of water and dumped them in the sink. After the second bucket, the display read “20.” Not bad for a 55-gallon tank, and after 5 buckets of water I expected to see “50” but instead was surprised to see “48.” I added a half a bucket and the display read “51.” Impressive!
I repeated the same test with the black tank with similar results. Needless to say, I was quite pleased. So, I marked the location of each sender with a wax pencil and proceeded to remove the duct tape. Ooops! If you choose to follow the manufacturer’s suggestion and tape the senders in place for testing before permanently adhering them to your tanks, let me offer some advice. Do not put tape over the serial number sticker! Removing the tape also removes the serial numbers. Anyway, I removed the backing from the senders and permanently stuck them to the tanks.
DISPLAY #2: This is where the SeeLeveL II™ system really shines. I was able to install a secondary display inside my shore power electrical bay so I can easily access it while I fill and drain the tanks. Now I can tell, with certain accuracy, how full each tank is when flushing and filling, without going back and forth and in and out to “see” the “LeveL”.
The real testing came with actual use. Some of my observations were surprising as I left the original wiring intact to the black and fresh tanks so I can compare the readings. I found that when the fresh water OEM gauge read empty, the SeeLeveL read 40% full and when the OEM read full, the SeeLeveL read 85%. The reading for the black tank was nearly identical to the discrepancy found in the fresh tank, proving the SeeLeveL II™ 709 system is well worth its $179 price tag.
There are 7 models in the SeeLeveL II™ 709 series. Some include water pump/heater switches and a few are capable of monitoring 4 holding tanks, so there’s one to fit your needs, ranging in price from $225 for the model 709 to $281 for the model 709-4-PH, which has built-in controls for your water pump and water heater, as well as monitors, and 4 holding tanks (fresh, 2 grey, and black). The additional model 709 display sells for $96. For those of you with 2 fresh tanks, you should look into the model 712FF that monitors 2 fresh, grey, black and LPG. To see all the SeeLeveL products available, visit Garnet Technologies on the Web at www.rvgauge.com.