They make the float type switches that ranchers use on their water troughs for cattle. The float on them is about the same size as the one on the kent float switch. The cattle trough floats can stop the full pressure of a water hose but with any plastic part after long periods of use they begin to wear out and start letting water pass. The good thing about the kent float switch is you aren't going to have any pressure pushing the water except for gravity. I think you could have quite a bit of water in the resevoir and I think the smaller diameter hose you are using will not put a lot of pressure on the float.
Brandon
