FloodStopWater Heater Leak Detector Kit with Automatic Water Shut-Off and Visual/Audible Alarms, 1/2" NPT MIP x FIP

Although this is sold for protecting against a water heater leak, no reason you can't install it on your main water line and locate sensors appropriately. Then, if (and that IS a big IF), a leak occurs where it'll wet a sensor, your whole house is protected against a, well, flood due to a plumbing problem.A good point, the valve is a full-port ball valve so won't restrict water flow.Somewhat negative is the price and availability of additional sensors if you want to string up a bunch of them. And the connecting wires are a bit short for use as a whole-house system, although it's just wire, you can splice in more.Haven't had it trigger in a 'real' situation yet - I do have a bit of concern, if something goes wrong and the valve closes, there's no mechanical way to override it, better hope the electronics never fail.

I Have installed a FloodStop on every house I have . Comming home to find your water heater leaking under pressure and you home flooded is the worsted . This unit sized for your supply is the very best ever. The money spent for this unit is really proactive over a flooded basement . This is a great unit.

Everything went well.