Due to the current drought in the Western Cape, South Africa, I was forced to convert my toilet to run from a greywater system instead of the local water supply. I designed a submersible pump controller with a float switch inside the toilet cistern to switch the pump on when required. The switch inside the housing is a standard reed switch from an alarm system. You need to use a small magnet inside the trigger arm to activate the reed sensor. The whole switch cavity can be sealed using either silicon or hot glue to prevent moisture entering. It needs a 1/2'' irrigation nylon nut that is glued onto the end for mounting purposes.

This float level switch can be used for many applications.