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Using Your RV : RV Systems

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Can you trust your RV gauges?
Russ and Tina DeMaris

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Somewhere in your RV is a control panel that, when pushing a button, you're told the status of your RV tanks. Fresh water, gray water, black water, and electrical battery charge. Many RVers are dismayed when they find those tell-tales don't always tell the truth. What's the deal?

The gauges in your waste water tanks are perhaps the biggest liars of all. The reason? It's in the design of the system. The typical RV holding tank gauge works by running a flow of electrical current from one tank probe through the fluid (be it black or gray water) to a another set of probes. The "receiving" probes are placed at different heights in the tank, close to the bottom, in the middle, and near the top.

The theory is that the electricity will route through the fluid (being an electrical conductor), and when you press the "test" button, lamps will light up, indicating which probes are submerged in fluid. Hence, if the bottom and middle probes are immersed, the lights showing 1/3 and 1/2 will light up, indicating your tank is over half full, but not yet 2/3 full.

The problem is this: Tank probes can get "gooped up" with muck from the holding tanks, particularly those in the black water tank. Then electrical contact can be made between all the "receiving" probes, and a bone dry tank can "show" it's full. This can make for a nasty feeling in the pit of your stomach, particularly when "out in the boonies" and planning to stay put for several days. Gray water contents can do the same thing.

How do you cope with this evil? There are various nostrums and approaches to cleaning up tank probes. Some are chemicals that are poured into the holding tank via the toilet and down the sink drain; these sometimes work, sometimes don't. Others suggest various wands and holding tank add on devices that flush the tanks with high pressure water, theoretically cleansing the tank probes. Again, these may or may not work, depending on how much goop has built up on the probes, and how faithful you are about frequently flushing your tanks.

Others take a different tack: After dumping the black water tank, some RVers are known to throw a bag or two of crushed ice down the pot, topping the tank off with fresh water, then taking a vigorous drive around the neighborhood to allow the ice chunks to knock crud off the tank walls and probes. Others simply resort to replacing the probes and hoping the issue doesn't recur too soon.

Other holding tank monitoring systems take a different approach to their readings. The SeeLevel system uses digital technology to transmit signals through the tank walls, hence no probes in the tank to get gooped up. The company says their system will warn if sludge begins to build up in the tank, allowing you to get rid of it before it creates a dumping problem. This aftermarket product isn't inexpensive--a 3 tank monitoring system runs nearly $200.

What's to be done? If you buy a new RV, keep your tanks flushed regularly to keep the probes clean. If you've got a rig with probes already causing you grief, take some of the steps outlined to try and "clean up" your probes. Seasoned RVers come to learn their habits and usage rates, and often can tell you just when it's time to dump the tanks based on their own experience.

What about battery monitoring? That's a whole different can of worms, and we'll tackle it in a future entry.

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