I'm looking for the device that Richard and Kevin demonstrated in the loft that automatically cut off the water when a burst pipe was detected. They demonstrated it, IIRC, by hooking a hose to a sink, running the faucet, then cutting the hose.
I am not talking about the washing machine cutoff that only provides pressure then the washing machine is turned on, nor am I talking about any of the various electrical devices that have a water sensor to detect a leak.
The one I'm remembering was activated when the water flow became completely unrestricted and, I'm pretty sure, was completely passive; no electronics or electrics or anything.
Help me out; this is driving me nuts!