Auto Water Change ideas???

[Doo]

here is my idea:

I want to use a lawn sprinkler type valve/ switch off a "T" on the drain going to the sump. once the valve is open, the water will go down a floor drain (tank is in the basement). this will run on a timer for once or even twice a week (small amounts at a time). Once the time is up - the valve shuts. The pump in the sump will continue running and this will cause the sump to fall low in water level. The low water level in the sump will then trigger an auto top off switch that will fill back to the right level.

This is big picture - detail needs to be ironed out...

what do you guys think?