FWIW... Much to my amazement, there are different internals used in float switches! Reed switches, sliding contacts, mercury vials... you name it.
The hardest thing to design into a float switch is a 'dead' zone between 'on' and 'off.'
I have had much, much better luck, and better reliability, with the ones using mercury vials.
What is interesting is that the vials have a partition inside, with the effect of making the cylinder act like an hourglass. The float has to move significantly from horizontal for the mercury to flow into the other half. This leads to a 'definite' switching action, rather than a 'maybe.'
If your local plumbing supply doesn't have them, e-mail me for a reccomendation.
