Quickly and safely isolates a fixture or appliance via an integrated 1/4 turn isolation valve John Guest push-fit polypropylene John Guest Speedfit to John Guest Speedfit push-fit shut off valve isolates supply to a fixture or appliance. Fast and simple to install, John Guest valves create an instant push-fit connection and leak tight seal without the need for tools, hot works or sealing agents. The unique collet locking design firmly and securely holds the pipe in place without deforming the pipe or restricting flow. John Guest push-fit valves are corrosion resistant and fully demountable, improving system performance and reducing system downtime during maintenance.