Flowlok Water Shut Off Valve 1/4" FLK-14 is a great device that installs right below your under counter water filtration system quickly.

No special tools are required and it does not need electricity to operate.  Flowlok leak Detectors utilize a highly compressed Safety Disc that expands when it absorbs water.  Once the Safety Disc has detected water it expands and trips the flowlok Safety Lever to shut off the water entering the water filtration device.

Safety discs are replaceable and are economical.