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Digital Tank Monitoring System




Tank monitoring systems have been around since the very beginning of RVs. They really haven't changed very much and they quite frankly have plenty of room for improvement. Most tank monitoring systems today consist of a bank of sensors mounted through the side of a holding tank at the Empty, 1/3, 2/3, and Full positions. Whenever the fluid inside the tank contacts these sensors an LED will light up indicating just how full that tank is. These sensors are the same as used on fresh water, gray water, and black water holding tanks.

The problem is that these systems really aren't that accurate. For one thing, they are susceptible to fouling. Various tricks range from dumping water softener or other chemicals into the tanks to dumping bags of crushed ice into the tank and then driving around to knock the crud off of the sensors. Even when the sensors are clean they still don't give really accurate readings. If you have a gray water tank that is filled to around 60% your LEDs will indicate that it is only 1/3 full because the water level has not yet reached the 2/3 sensor. Conversely, your fresh water may be between 34% and 65% full and it will indicate 1/3 on your LED display. As soon as you run a quart of water through the faucet that LED may read empty if you were at the 34% level or it will still read 1/3 if you were at a higher level. You just don't know exactly what you have.

Fortunately there is a solution. Garnet Technologies has been making tank monitoring equipment for the petroleum and other heavy industries for a long time. They have developed a great system designed for RVs that addresses all of the shortcomings of the typical system. They have a website at www.rvgauge.com that showcases the SeeLevel tank monitoring system for RVs. I chose to purchase my SeeLevel sensors from RVupgrades.com because I have had excellent service and support from them in the past.

The SeeLevel system is unique in two ways. First, it uses external tank sensors rather than internal sensors. Unlike internal sensors, external sensors are not subject to fouling because they are never in contact with the tank's contents. These sensors simply stick to the outside of the tank with a 3M based peel off adhesive. They use some sort of density monitoring radar to tell where the tank level is. Okay, so maybe it's not exactly radar but it sort of works like it. After all I only install these things, I didn't design them. ☺ But, it does have the ability to see right through the tank to see what the level is.

The second advantage is that this information is a sampled continuously along the length of the sensor strip. This information is reported to the tank monitoring panel which reports this information on a digital LED readout that reports the level in percents. It is accurate to 2% so when your tank is 62% full it will show a 62 on it's display rather than lighting up the 1/3 LED on the old systems. This gives you a better idea of how full your tank really is so that you can make a better educated decision on when to dump and/or fill. In addition the SeeLevel system can tap into the existing LP tank sending unit. Because the existing LP tank sensors are a variable rheostat the SeeLevel system can report in 2% increments on that as well.

SeeLevel panels come in a wide variety of sizes and configurations. In addition to the Fresh, Black, and Gray tank displays, battery voltage is typically displayed on most of them as well. Other features can be LP tank level, inside temperature, outside temperature, and even switches can be found on some models to control water heaters and water pumps. It's also possible to connect multiple panels within a system. I chose to install a larger SeeLevel panel in the galley while mounting a smaller panel in the water service bay. That way I can monitor the tank levels while at that station.

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Mark Quasius - "Cruzer"




The Installation

There's two basic ways to install this system. Method one is to use the existing tank sensor wires, relocate the wires from the old sensors to the new and then replace the existing monitoring panel with the new one. Method 2 is to start from scratch and run new wires.

I chose the second method because Tiffin's monitor panel is a fairly large unit that contains switches for the slide-outs as well as the HydroHot controls. Rather than rework everything I chose to just leave the existing system as it is (there's no problem with having both systems in place) and run a new system for the SeeLevel. Besides, I wanted to relocate the main monitor panel to the hallway where it's more convenient to access.

In the hallway of our 42QRP we have the OEM light switches, fan switches, and thermostat for the heating and cooling systems. I have installed my remote panel for the energy management system as well as the system control panel for the Xantrex RS3000 true sine wave inverter. These items were installed directly above the OEM switches and thermostat.

Directly underneath the thermostat is where I chose to install the SeeLevel main panel. The particular panel that I chose for this coach was the SeeLevel 712TT, which includes Battery Voltage, Fresh Water Level, Gray Water Level, Black Water Level, LP Tank Level, Inside Temperature, and Outside Temperature. Because I already had an outside temperature unit I mounted the remote temperature sensor in the basement water compartment to keep tabs on the temperature in that area during cold weather.

     hall panels



In order to display any of these readings you simply press one of the buttons on the membrane and the reading will display for about 3-4 seconds. If you press it twice it will lock in and continue to display that reading for a couple of minutes. By default this particular panel will display inside temperature when no buttons have been recently pressed. I also installed a smaller SeeLevel 711 panel in the basement water service bay that simply displays Battery Voltage, Fresh Water Level, Gray Water Level, and Black Water Level. I find this to be a real help when servicing the tanks. By default this panel displays nothing until the buttons are pressed.



The SeeLevel sensors strips are the green plastic items shown in the above image. They are flexible green printed circuit boards filled with a bunch of electronic components. Everything is sealed over with some sort of clear coating to keep everything working in moist conditions. The strips can be trimmed on the bottom end if they are too long for your particular tanks. Each sensor has one wire that leads to the panel as well as a common ground wire that can be shared amongst all of the sensors.


sensor CU

One thing to remember is that the SeeLevel sensors cannot be installed with any steel within 2" of the backside of the sensor. For this reason I had to modify the steel framework surrounding the gray water tank and cut a chunk out in order to keep the steel frame from interfering with the sensor. I had to do the same thing on my 2004 40DP and found no negative effects from this. I then wrapped the entire wiring system inside plastic convoluted wiring loom and ran the wires to the other side, where the SeeLevel 711 panel was located in the water service bay, and then up into the galley to connect to the SeeLevel 712TT display.



This is a pretty slick system. It's foolproof and doesn't require any maintenance and you can get very accurate tank reading whenever you want. It also gives you the ability to locate these panels wherever you feel they are convenient. Hopefully more RV manufacturers will utilize these systems as standard OEM equipment. Country Coach and many of the larger Prevost conversion builders utilize these systems. They're really not that expensive, as any trip to RVupgrades will show, and it's one of the best returns on investment that you can make. For further information I've posted the following manuals on the website for you to download or view if desired:



This review written 11/6/06



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