Waste Tank Level Wiring Question

[TallPaul]

My motorhome has 35 gallon grey and 35 gallon black tanks. I took my first trip in the spring and noticed that the tank fills pretty quick, so we were dumping twice per day. There are only four of us and we don't use the RV shower, nor run cooking water down drain (either eat cold stuff or eat out). So mainly water from washing hands and brushing teeth.

Yesterday we took a local day trip with the motorhome and were out 6.5 hours. When I parked it at home and hit the level indicator switch grey flashed the 4th (full) light then receeded to three lights. It stayed on three steady. Then I drained off the grey tank in 2 gallon increments. After the first 2 gallons were drained off, it only lit up two lights. I drained the tank empty. There was a total of 9 gallons in it when three lights were on and the 4th light was flashing. Looking at the side I can see the highest terminal is pretty low on the tank, so I figure they installed the terminals too low.

1) Can I get a kit to install new terminals at better levels or do I just use a stainless steel screw and washer, which is what it looks like is in there now?

2) What kind of glue do I use around the terminal to ensure it never leaks?

3) Do I correctly understand the wiring? It is as follows:

There are 4 terminals on the side of the grey tank.

Two terminals are near the bottom (maybe 1.5 inches up) and spaces sideways but both at roughly the same level. One of these has a white wire and the other a yellow wire.

Several inches higher is a terminal with a blue wire, and above that is a terminal with two wires--a green and a white.

So, I assume that the first light is on even if the tank is dry (which seems silly but...). Then the second light comes on when the water touches both the white wire terminal and the yellow wire terminal (completing the circuit between those two). Then the blue would light the third light and the green (with also a white wire) would light the 4t light.

If that is the case, I can measure the tank and try to estimate the height that would give a more accurate indication of fullness. Then I can install new terminals. Seems to do the job right, I could use the existing blue terminal (third light) for the second light, and just install one new terminal higher up.

Thanks very much, Paul

[TallPaul]

My motorhome has 35 gallon grey and 35 gallon black tanks. I took my first trip in the spring and noticed that the tank fills pretty quick, so we were dumping twice per day. There are only four of us and we don't use the RV shower, nor run cooking water down drain (either eat cold stuff or eat out). So mainly water from washing hands and brushing teeth.

Yesterday we took a local day trip with the motorhome and were out 6.5 hours. When I parked it at home and hit the level indicator switch grey flashed the 4th (full) light then receeded to three lights. It stayed on three steady. Then I drained off the grey tank in 2 gallon increments. After the first 2 gallons were drained off, it only lit up two lights. I drained the tank empty. There was a total of 9 gallons in it when three lights were on and the 4th light was flashing. Looking at the side I can see the highest terminal is pretty low on the tank, so I figure they installed the terminals too low.

1) Can I get a kit to install new terminals at better levels or do I just use a stainless steel screw and washer, which is what it looks like is in there now?

2) What kind of glue do I use around the terminal to ensure it never leaks?

3) Do I correctly understand the wiring? It is as follows:

There are 4 terminals on the side of the grey tank.

Two terminals are near the bottom (maybe 1.5 inches up) and spaces sideways but both at roughly the same level. One of these has a white wire and the other a yellow wire.

Several inches higher is a terminal with a blue wire, and above that is a terminal with two wires--a green and a white.

So, I assume that the first light is on even if the tank is dry (which seems silly but...). Then the second light comes on when the water touches both the white wire terminal and the yellow wire terminal (completing the circuit between those two). Then the blue would light the third light and the green (with also a white wire) would light the 4t light.

If that is the case, I can measure the tank and try to estimate the height that would give a more accurate indication of fullness. Then I can install new terminals. Seems to do the job right, I could use the existing blue terminal (third light) for the second light, and just install one new terminal higher up.

Thanks very much, Paul

[paz]

Paul, it seems as though just about everyone has had problems with through-the-wall tank sensors at some time or another. For us, the black was always worst followed by the gray. The fresh water usually works pretty well.

The problem is suspended particles in the black and gray water accumulating on the sensors. I don't know if replacing the sensors will solve the problem. Doing so may help you get more accurate positioning of the sensors; but IMO, the new ones will eventually foul and send false readings like the originals.

There are additives you can put in the tanks that supposedly clean the sensors, but I don't know how well the additives work. I have also read about various schemes of adding dish detergent and ice to the black tank then driving around to clean the sensors. I would think it would take quite a large amount of ice to make a difference and, of course, the ice can only be added to the black tank, not to the gray.

As an alternative, I would like to suggest SeeLevel Tank Gauges from RVUpgrades. We have the 709 SeeLevel II model. The sensors mount on the outside of the tanks so they can't foul. The system uses the wiring from your existing sensors so it's not too difficult to install. Readings are in percent are quite accurate and repeatable. Knowing the capacity of your tanks, you can easily calculate how many gallons are in each one. If your motor home has an LP tank level sensor, SeeLevel will use the existing sensor to give you accurate LP readings as well.

There was a thread a while back on the SeeLevel gauges. Try using the "Find" tab above. Uncheck the box to search the entire forum. I think one member even posted photos of his installation.

[TallPaul]

Thanks, SeeLevel is pretty expensive, but very nice too. I'll have to look into it. Not sure how it reads through the thick plastic walls.

I don't think I am getting fouling problems, but that the tanks are L shaped with the L on its face, that is the long stick is horizontal and the bottom of the L points down as a well for the drain part. Problem is that the sensors are in the well part, and all but the 4th light sensor are below the level of the main part of the tank. They probably would be in the right location if the tank were a simple rectangular layout, so moving the sensors probably will work best.

My plan it install a new terminal above the existing then move each connection up one sensor.

Anyway, can I just use a stainless screw and washer?

And what glue? Household Goop, silicon sealer?

[Ray,IN]

I too have noticed sensor placement appears to be haphazard. Low wages attract-er- I'll quit.
Silicone sealant is perhaps the worst product for the RV market. The SST screws are a good idea. Have you considered using ordinary plumbers putty or butyl sealant instead of silicone? It will stay flexable and is a good sealant.

[RV Wizard]

A component called a well nut is needed to install a new sensor in the side wall of a tank. It is a rubber jacketed threaded brass barrel that will fit into a hole and when the screw is tightened it swells the rubber to create the seal in the tank. Kind of acts like a molly fastener.

[TallPaul]

Thanks RV Wizard. I will get a couple Well Nuts, one for each tank.