Lately we’ve noticed empty isn’t really empty according to our Airstream’s tank monitor. When we first got her, the Big Weaz’ tank monitors read 2 dots when empty. After 6 months of fulltime RV living, “empty” has become 4 dots (or 3/8ths full). Thats no good!

What the heck is a tank monitor?

Airstream Tank Monitor, Circa 2011

Let me take a step back for those of you not yet living the RV lifestyle. Living in a house, you can basically forget what happens to waste water once it goes down the drain. In an RV, the buck certainly doesn’t stop there. Your “gently used” water goes on to fill your black (toilet) and grey (sinks / shower) holding tanks until you manually empty them out. Failure to empty these tanks when they fill up leads to some hilarious Robin Williams-esque scenarios that I hope we never experience.

Since RVers aren’t born with an innate sense of “fullness” when it comes to our waste water tanks (or, in some cases, our stomachs), we need to rely on technology, experience, and math to determine just how full these tanks can get. Nowadays, RVs come standard with all types of consoles and doodads that tell you the state of your tanks. Most monitors today give you the basic info, but most have the same modern look and usability of the Bat Computer from the old 60’s Batman series.

Bat Computer, Circa 1966


It looks reliable, but can we trust it?

Now back to our story. After watching “empty” change meaning over the past few months, we became suspicious. So, off to Airforums for a more layman’s explanation of things to try.

Airforums recommended I first clean the tanks like never before, and that’s exactly what I did. I filled and emptied the tanks twice. I applied a healthy dose of borax to both my tanks, just to make sure things were nice and slippery inside. Still, the black tank blinked 4 dots at me when empty. So, according to airforums, my next move was to”recalibrate my monitor.”

How does one recalibrate holding tank monitors?

Being a bit of an electronics nerd, I rarely step down from a challenge. So, with manual in hand,  I stepped up to the monitor and started following the directions for recalibrating. It turns out that the manual for the Bat Computer would have been easier to follow.

First off, the instructions don’t really warn you that there is not a “reset to factory” option, which makes sense I suppose, but would be a nice feature to have. As it stands, recalibrating requires you to empty and fill your tanks to get an accurate measurement.

This was one of the first gotchas I found while recalibrating. Since the procedure for recalibrating your tank monitor may be different, I won’t go into the specific directions. But I’ll give a few helpful hints I wished someone would have bestowed upon me before I took on this little adventure:

  • You really need to make sure the tank is super clean before starting – rinse them out a few times, drop some ice down the black tank and drive around, whatever it takes to make sure you’re not just dealing with a dirty sensor.
  • Know the exact capacity of your tanks – and subtract 1-2 gallons for “wiggle room”
  • The Tank Monitor is not an exact instrument – it gets you close enough, but don’t expect it to be dead on accurate.
  • Check the tank monitor manufacturer’s website for an updated manual. Who knows? They may have an updated one that doesn’t require a PhD to follow!
  • Ask yourself – do you need to recalibrate ALL tank monitors, or just one of them?  Recalibrating ALL tanks can be a LONG process. Have a full day with nothing to do.
  • Have a measuring bucket – I used a 6 gallon bucket to measure the amount of water I poured back into my tanks.
  • Don’t have a measuring bucket? you can approximate if you know the gallons per minute of your water source. For example, I know my shower head spits out water at 1.5 gpm, so 2 mins = 3 gallons.
That’s pretty much it. Have you ever recalibrated your tanks? Was it a good experience or bad? Has anyone found an easy to use tank monitor upgrade for Airstreams? We’d love to hear about them!