No no, none of those:

Go to some of good hotel in your town.

Go inside their bathrooms of at least two rooms.

Open up the flash tank. (imagine 007 music in the back ground)

Remove the floats and climb down the monkey rope out of windows of the room.

Install those floats in your water tank, one for full and one for empty, taking care of hysterisis.

Just attach relays to floats. Hook up you pump motor thru these switches.

That's the end of the show.

Good Luck

BL/