This is just a thought regarding this subject and doesn't involve electronic solutions.
Heretic!
Although simple is good, over-engineered is much more fun.
Might I suggest that the float is connected to a modified DS10a which will send a security signal to an always-on computer to decode to a standard X10 house/unit code that is sent to a universal module that opens and closes a relay connected to a washing machine valve that in turn supplies water to the pool.
One should also consider that this could be further complicated by use of another similar set-up that will drain the pool if the water level is risen too high by excessive rain.
With a little inventive plumbing and a timed macro or two combined with a pump or three, it should be possible to deliver a small sample of pool water to your kitchen sink to monitor chemical levels AND automatically refill the pool to the optimum level.
There are, I believe, computer controlled chemical analyzers whereby you could (probably) have your sample checked (at your kitchen sink) and have the chemical levels adjusted automagically.
KISS has absolutely no place at my house. Heath Robinson (or Rube Goldberg) aint got nothing on me