hang on overflow backup idea

[beaker020]

The Madison M8000 is the standard float switch used by many. I special ordered one at Acklands-Grainger a few years back, cost me $20. You can pick up similar ones on eBay periodically for much cheaper. This site http://www.aquahub.com/store/index.html has all the supplies and DIY info too. MAKE SURE you use a relay.

This application is identical to an auto top off system except you may need a higher power relay and you would reverse the float if you decided to put it in the sump.

You could design a latching relay setup to prevent cycling. Let me know if you need help with that. I could bang up a schematic if need be.