water level controller

hello everyone
i am trying to make water level indicator and controller using cd 4069ube and cd4066 ,
with cd4066 i tried to make only indicator and siren when tank full but that circuit is not proper working,this works 8-10 days properly then got disturbed.
then i tried with controller and cd4069be the automatic water level contrroller then it also works for some days. sometimes the sensor which i put in water tank get a layer of slat and rust,
sometime getiin problem with earth and ground.
so with all i am getting trouble so please help me..
give me some idea and your apllied circuits so i can try that also.
thanks in advance

How you are sensing the water level ?
Is it one Common electrode in water tank and other on level top for for max surface contact?

Had to check on the internet. Rust is not a conductor. (If I ever knew it I forgot.)

Are you using an electrode made of iron or steel? This accounts for your circuit working okay at first. A coating of rust inhibits operation.

I was about to suggest that you use an electrode made of lead, or solder containing lead, or wire pre-tinned with lead-bearing solder, etc. However that is likely to add bits of a poisonous substance to the water. You don't want to do this, particularly if there are living creatures in the water, or if the water is for drinking (or bathing for that matter).

Practically any material would oxidize or accumulate some kind of coating. Now gold would be okay to use as an electrode, but an ounce of it costs $1,630.

It's best if you don't put wires in the water. A float switch may work for you.

For example, rig a ping pong ball to rise up and push up on a wire to keep it from contacting a second wire. When water level drops, the ping pong ball drops, and the wires touch.

without the circuit diagram it is difficult to say where is the problem?
better use stainless steel rods for sensing

You MUST use AC through the contacts that are conducting in water, else you will get some eletrochemical corrosion or plating or the water will be electrolysed and gases liberated at the contacts that will cause them not to conduct.
Frank

This method of water level detection doesn't use electrodes or a float switch. It uses wire coils inside a plastic tube suspended in the water. It specifies the water must be conductive.

The article says the coils might even work when placed on the outside of the tank.

Circuit - Electrodeless Water Level Monitor - Circuits designed by David A. Johnson, P.E.

And by detecting capacitance between insulated metal plates:

Circuit - CAPACITANCE TYPE LIQUID LEVEL MONITOR - Circuits designed by David A. Johnson, P.E.