Auto top-off failsafe

[kfowler]

I'm looking for some protection against overfilling my tank with RO water.

Currently I have my Aquasafe RO/DI unit plumbed directly into my sump, which is controlled with a Kent float valve. The RO unit has a built in shut-off kit so the unit isn't pumping water down the drain while the unit isn't in use.

My worry is that if the float valve is stuck in the "open" position and fills my tank with fresh RO water, killing my tank, and flooding my house.

I would like to rig in some type of sensor/actuator that senses this overfilled condition and shuts off the water entering my tank. Does anyone have anything like this in their setups?

Any help would be appreciated.