Waste water tank guages not reading correctly

[tiinytina]

Sent: 5/29/2007

Hi. ho,
    The nice interior control panel LED lights read the LPG and battery life correctly. The readings on the grey water tank however never go above 1/3, though we've had water backing up into the shower because it was over full. I traced the wires and see them (ok they are coated in blow insulation under the rig). Can tell there are 4 of them attached to the tank. I have not scraped away the insulation for a closer look yet. So the question becomes how are these things connected to/into the tank? Are they replaceable?
Thanks
Tina

[Slantsixness]

Sent: 5/29/2007

They are replaceable, but it's possible that they're either coated in Soap, or some other food stuff, or the base sensor has come loose.

What happens is this:

Water and soapy water conduct electricity (although not very much, nothing harmful... remember the lemon with two unlike metal plates that turns on a little light bulb? sort of similar, but far weaker conductance.)

How it works:
insert 1 metal probe into the water at the bottom of the tank. Insert another sensor  at 1/3, 2/3 and full. (or at 1/4, 1/2, 3/4 and full in some units.. doesn't matter how many, but you really don't need more than 3...)

when the water reaches the first 1/3 sensor, the 1/3 light comes on, because there is conductance between the main and 1/3 sensors.

Some have up to 6 sensors. and all they are is little metal (stainless steel) buttons that go through the tank. Most of the original tank sensors are molded into the tank. Replacement means you have to drill holes in your tank ( Ug!) and then seal them up.

There is a product, that is like a molly bolt, where you drill a hole, insert the new sensor and tighten it up and it seals itself, except it doesn't work on Fiberglass tanks... they'll crack!... (I don't know which you have... if it's ABS, you're in good shape here.)

try this:

run a wire down the drain from the sink. make sure  it is stripped back a 1/4 ", and that it touches the bottom of the tank. (not easy to do but a couple tries and it'll be there)...
Now, connect the main sensor wire to the wire down the drain. Does the system suddenly work all the way to full as you expect? Then the main (lowest) sensor is bad.
IT only takes a few minutes to test,  and find out if your panel is just hosed up, or perhaps only two of the LED indicators are working...

the same test wire can tell you weather the 1/3 2/3 3/3 sensors are working. just try the individual connections on the drain wire you inserted. (But reconnect the main sensor wire (provided it was good!) when you test the individual level sensors.

Am I boring you?

I can send you a  mock up schematic of how to test them....

If you have ABS tanks, the replacement sensors are peanuts, and available at most RV stores, if not... RV surplus has them.


Ok.... Another thing I've learned over the years.... lots of soapy water will make the sensors read full when they're not, and empty when they're full. This test will tell you if your sensors ar deteriorated or bad, but it won't fix them or clean them!

Now...How to clean them... and yes, this DOES work....

Use DRY DISH WASHING DETERGENT for your dishwasher. Yes.... the DRY stuff, the wet stuff will just make more mess.....Cascade Electrosol, Cheap store brand, I Don't care.... But POWDERED, for sure and NO JET DRY!!)
Empty your Gray tank. how big is it? use 1/4 cup DRY Dish washing detergent powder to EACH gallon it holds. (regardless what it says on the box)
Fill your gray tank (Slowly, it's gonna foam... you want that) with as clean a water you can get out of a garden hose, but preferably relatively sediment free. (If you'll drink it, it's good enough.)
Let it sit for 2 FULL days.   
If you want to, Drive the Motorhome around the block once or twice. (agitation) again, after it's done it's two day sit....
Empty the gray tank. Fill and flush again with just water. Note when you refill it, your sensors probably will start working again!, but flush it again to get all the "soap" out.
You can do this with your black tank too, but it's a potential mess you probably won't want to deal with if something goes wrong... that blue stuff will stain your driveway, and your hands for weeks!  (and don't use that wintergreen stuff from wally mart... it doesn't work; and smells like Mr. Wrigley and Mrs Trident Gave birth to Double mint in your toilet. (I'm not exaggerating, that stuff is AWFUL!)
There are Phosphates in the Powdered dish-washing detergents that will clean stuff up amazingly well. Be sure to take precautions when dumping your tank. I don't recommend dumping it directly on the ground in tidewater areas... send it down the city sewer or your septic tank... that'll save the critters in and around the Bay.

so... Try it! Pat will be happy he doesn't have to tear yet another counter or cabinet out and redo it! and if it fixes it, Yippie!

Tom

[enigma960080]

Sent: 5/29/2007


Yeah, thats  it... what  Tom said...

I  tried  all that stuff  with the black tank  on my Superchief,  No Joy...

Not  to say it  won't work  for you,  but  by the  time  I  filled agitated and  drained  3 or 4 times,  it was  easier  for me to  replace the sensors.  I  had  8 on mine.  I  think  they  were  4 or 5 bucks a piece.  I will  look through  my email and  see if I  still have the  info.

[tiinytina]

Sent: 5/30/2007

thanks guys! First I'll check the LED's.... Since we are meeting up with Brad next weekend... I may try the dishwashing powder cleaning trick... I do also have a container of triple phosphate I didn't use to clean the roof.... and maybe 2/3 fill the tank to get a good slosh factor over the 2+ hour drive to Da Pond... Can empty on the way in at the dump station.... and rinse....

Tank seems to be original but there is so much blow insulation over it I don't know what its made out of. I have a feeling its fiberglass....

thanks!
Tina

[ClydesdaleKevin]

Sent: 6/10/2007

Hey Tina!

There are 2 types of tank gauge sensors.  Most Winnies have the good/easy type...just screws that go into the tank at various levels with wires attached to them.  Some have the type we have in a retrofitted tank:  A long ceramic thingy with electrodes, where all the wires attach at the top.  It thats what you have, the electrodes could be corroded...mine were.  I soldered in new wire and replaced the electrodes, cutting them to the same length and pushing them into the original grooves, so now it works on my freshwater tank...my grey and black are still the original good/easy types.

Kev

[tiinytina]

Sent: 6/20/2007

Thanks Kev, Haven't had time nor inspiration to chip off the insulation to see what is under there yet..... Need to buy a can of that expanding foam stuff when I do have time and inspiration though...  Let you know how it goes.
Thanks!
Tina

[melyash]

Sent: 9/29/2007

Before you do all that, if there is just gunk on your sensor probes in the tank, fill your tank about 1/2 full with water, pour in a couple bags of ice and drive around town. the ice is light enough it won't damage the sensors and they bounce around a lot cleaning the inside of the tank. Wait for them to melt and drain as usual. This trick has worked for many people

[tiinytina]

Sent: 10/11/2007

I can get the ice into the black tank through the toilet no problem... just no way to get it into the grey tank unless I rip out the shower drain.....
Tina