RV Tank Sensors &The GEO Method
Almost every RVer I know complains about their tank sensors. It’s almost a given that after a few months the sensors start acting up and giving false readings showing tanks that are full when they are really empty. For anyone who dry-camps alot this is kinda annoying, and most end up just “living with it”. But there is hope! We’re not tank wizards by any means, but in 2 years of RVing we’ve managed to keep our black tank sensors working perfectly with our grey sensors OK most of the time. And most of it is thanks to the GEO method.
Now to understand why tank sensors go bad it’s worth understanding a little about how they work. Most RV tank sensors are basically just 4 screw probes that stick into the tank. When liquid hits the screw it makes contact & completes a circuit that turns the LED light on your panel on. Over time crud and slime covers the screws causing connectivity when there really is none (so sensors “think” the tank is full even if it’s not). It’s a really poor system, but it’s a cheap one which is why it’s so widely used. So, the key to making these things work again is simply to clean off that grime. Easier said than done, right?
There are a ton of cleaners, tank chemicals and what-not out there each of which have their passionate supporters. Also there are much better sensors such as Horst Miracle Probe and SeeLevel, both of which get excellent reviews. But for those of us with old sensors and a cheap pocket, this is the method that’s worked best for us:
1/ Never Dump Until Tanks Are At Least 2/3 Full
Waiting until your tanks are full before dumping helps keep things liquid and pressure high so that when you finally pull the plug “stuff” comes out rather than drying out and building up as pyramids in the tanks. So, even when we’re fully hooked-up we keep our tank valves closed until we’re ready to dump.
2/ Dump Black First, Then Grey
Always dump your dirtiest (black) tank first before dumping your grey. For those of you not in the know, the black tank contains run-off from your toilet, while the grey is run-off from your shower and sinks.
3/ Use Lots of Water & Back-Flush
Using lots of water (when you can) really helps to keep things flowing in the tanks. We’ve got a factory-installed back-flush system in our black tank and after we dump we’ll usually back-flush and re-dump before heading out again. There are after-market back-flush systems that are super-easy to install and work very well too.
4/ Clean With The GEO Method
The GEO method is a home-made cleaning technique that’s been around in the RV community since (at least) the early 80’s. Where the name came from no-body seems to know, but the original method is HERE. The original formula uses chlorine, but that can ruin your valves so these days most RVers use a slightly modified method with just 2 common items, both of which you can get at any big department store:
- Calgon Water Softener -> This stuff helps to break down water surface tension, clean scum and prevent hard mineral deposits. I’ve used Borax on occasion when I can’t find Calgon and find it works just as well.
- Dawn Dishwasher Detergent -> The “original formula” blue detergent is excellent at cutting grime. Laundry detergent works too.
After you dump pour 1 cup of Calgon and 1 cup detergent into the tanks. Leave them in until your next dump. Before driving some RVers will also throw a bag of ice-cubes down the tank to “scour” their walls (we’ve never done this, but others swear by it).
And that’s really it! We don’t use the GEO method each time we dump, but just whenever our sensors need an extra cleaning. Either way it’s a simple, easy and environmentally-friendly method to keep sensors mostly clean. And in a moving house on wheels that’s really as good as it gets.
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