Tank fluid-level measurement

[RJ82much]

This topic is trickier to understand or define. I, like so many of you, just can't believe our indicator lights, especially for grey & black water holding tanks. We've been led to believe that that darn toilet paper is screwing up the reading.

From what I've read, there are maybe 3 ways that fluid levels are determined in an RV. Tanks could have holes drilled with sensors installed, or could have a single probe inserted in the tank with a similar type measurement, or could use an external method using the change in the electrical field due to fluids on the other side of the tank wall. I don't know what GSC uses in the waste tanks - haven't located their sensor yet. The freshwater is definately sensors thru the tank.

Regardless of the method though, just think how difficult it is to determine the level in a wide, thin, flat tank. My 50 gallon water tank, 7 3/4 inchs high, has 4 sensors, one each 1.7 inches or 12 gallons of water. A sensor probably can't see closer than 1/2 inch, or 4 gallons of water. IE, 1/4 tank of water remaining is somewhere between 8 & 16 gallons if the MH is perfectly level...

A similar analysis likely applies to your waste tanks as well, a mere 4 1/4 inches high or 1 inch difference between each 1/4 tank of fill. Introduce the same sensor inaccuracy & there could be 2 1/2 gallons of error in a 24 gallon tank. IE, a full reading (just above the 3/4 full sensor) could mean you can add another 3 to 8 gallons of S#%@. On top of that, the measurement is greatly affected by the level of your MH. Tip it slightly toward the sender end & it will read full. Lean the other way & your indication will be that you can "go" in it another day.

I don't have a solution, just acknowledgement of the inaccuracy of our readings due to the way they are determined. ...and very little to do with toilet paper

[ronbo]

Good point, Bob, and well-thought out. A narrow-diameter deep tank would be much easier to sense than our long flat ones, so we have to live with what we got. (Or I guess we could stand the tanks on end with the sensors down the side, and pump our waste-water to the top and fill 'em that way.... :D )

Though you are right-on with the levels being hard to measure with such a small differential, what has always irked me with the probe-types is that I can empty the black-tank and STILL get a full-reading. Rigorous flushing/rinsing, secret procedures, voo-doo chemicals, and so on never do fix the problem 100%. Nature of the beast.

BTW, I had an '04 8379 and it had the probes stuck into the tanks. As I understand it, the probe-system is the cheapest.... and most prone to give bad/false readings. Most waste-tanks aren't a perfect rectangle either, they usually are tapered or angled at one end or the other.

Thanks!
Ron

[RJ82much]

My waste water tanks are 4 1/2 inches high curb side & I believe 6 1/2 high on the driver's side, or tapered as you said. The aftermarket supplier wants an internal slope toward the drain & instructs the top of the tank to be level. The bottom will then have the proper pitch.

You realize, if you tip the tank so much to get a reliable reading, either the MH will fall over or you'll slide off the toilet... Ha Ha Ha, am I the only one laughing at that picture?

I would have gone to the trouble of calibrating my readings when the unit was new, if I had known about the inaccuracy. Now that they've been used, I think I'll skip it. Don't really feel like messing around filling & emptying my tanks at a dump station.

[GStream40]

Gulf Stream uses all probes that are merely a stainless steel screw screwed with a rubber surround to seal into the tanks with the sensor level wire attached to them. These are the worst to use, but it is also the industry standard because of low cost.

I"ve had 5 RV's from 3 different manufacturers and they were all the same inaccurate readings. One thing I did find out from a seminar is that you should hold the button in for a while, sometimes up to 3 to 4 minutes, and it will dry the "sensor" and give you a fairly accurate reading. Of course this usually works on the gray and freshwater. The black tank it will work as long as the toilet paper is not hanging on the sensors.

There are aftermarket exterior "strips" that stick to the tanks and one model that uses your old wiring for it's installation, but they are pricy.

Ron

[ronbo]

Hey Bob -

While you're "sitting there" visualizing the picture of someone slipping off their commode, how about a visual of how they check the big gas-station underground tanks for level. :shock:

See, you could have these little holes drilled thru the floor in the appropriate places to reach right down into the black/gray tanks. Then all's you need to do is use your awning-rod thingy and poke it down the hole to see if it's time to get up and go dump.

Come to think of it, I'd want to invest in another awning-rod to use for the awnings. :D :D :D

[Retird2Golf]

:twisted: Outside of boh of you being "stark, raving, mad, lunitics. :roll:
Youve got some good info. My gauge :arrow: is Green, 1/3 (still green) 2/3 (yellow) and "Go pull the handle , dummy" (red) :oops:

So ... for me it's check every morning and when It hits the red ...... :arrow:

:shock: Life is a beach :o