Tank gauges - how do they work?

I believe the "sensor" uses the liquid to close "the switch"... the same as those water alarms people place near water heaters. The problem is the "sensor". I assume this is just open conductors spaced apart. Any splash or high humidly would cause problems.

There is an aftermarket tank sensor system that I've heard is very accurate.

Most important thing to know about the gauges in the F/W, grey and black tanks is that they are notoriously INACCURATE....to the point of near uselessness. We picked up our brand-spankin' new TT and the gauge on the black tank read Full. Some folks have changed theirs to a brand that is supposedly better, but no info here on the brand or exactly how satisfied they are now. If you go into the members listing and look for Chuck_S, he made the change, believe he has pictures of exactly how he did it and all the info you'd need. He most often is on the hybrid side of RVNet. Others may have the same info.

Usually the F/W tank is pretty much correct. The grey is likely close, but the black tank is anybody's guess. The slightest piece of debris of any kind can make the sensors go crazy. Even a good flushing of the black tank can still leave just a speck of TP or other and it'll show an incorrect reading.

After some use, you'll be able to know about what level you're at with the grey and black. I found, nearly the hard way, that when the kitchen sink starts draining very slowly that it's likely backing up into the shower. Our system is to be stingy with water going into the grey tank and very generous with the water for the black. 3 - 4 days is about our limit on grey and that's with 2 of us.

Simplest answer based on most of what I've seen on here is "poorly" :B

I fixed mine. Only had to make one minor adjustment so far this year. If you read this thread you will find that I had nothing but negative response to any new ideas.

Thread

Wiring diagram of a common type:

Wiring

Simplistic explanation;
*screws through wall of tank at various heights
*wire connected to each screw
*current passes through the water to connect the screws electrically and complete circuit.

Most gauges are probes that are set at different levels in the tank. As the tank fills, the fluid acts as a conductor between the lowest probe and the higher probes. Sounds like a good plan and in an ideal world it would be.

Unfortunately instead of a tall skinny tank with wide spaced probes, many TT tanks are short and squat affairs prone to slaushing, so the probe spacing is not very wide and often shorted by debris or moisture that has bridged the probe gap. Add to this the fact that the TT or the tank or both may not be level, which will only add to the error.

My black water tank was constantly reading FULL, so I took the advice of some on the board and dumped in a 22 lb. bag of ice before I hit the road. Crude but effective, it scrubbed what ever was bridging the probes. I really do not want to know. :E

As previously mentioned, unless you are willing to tinker and calibrate, most folks find it easiest to just consider the readings only an approximate indication of tank status.

Typical thru the wall stud type......





Type of thru the wall studs....
Far right..OEM short stud
Center and far left...Horst Replacement Probes (Center/black---left/grey-fresh water)



Surface Contact electronic level indicator....See-Level Brand

bigorange wrote:
Simplest answer based on most of what I've seen on here is "poorly" :B

x2

Great information Old-Biscuit. I'm considering the Sea-Level System someday. Otherwise you just get used to knowing about where you are.

My "full" monitors work.. When empty, my tanks usually show around the 2/3 mark..

So really, once I see the "full" one go on, that's when I know it's basically full.

The rest, I don't really care about.. ;)

Besides, I use my 30 gallon fresh water tank for water and with a 30 gallon black and a 30 gallon grey tank, I won't ever fill them up before running out of fresh water first.. :)

Most folks don't "camp" like that, so it's not a system that works for for everyone, but works great for me.. :)

Good luck!

Mitch