Isolate the water supplies by means of the integral ball valves accessed underneath the tap spigot. Open the levers and allow residual water to drain. Remove the tap's bottom cover using a strap wrench. Loosen the tap's retaining screw until the head is just proud of the inner body. Pull the Optitherm away from the wall to dismount it from the spigot. A replacement tap can be installed and commissioned in a matter of minutes while the original tap can be removed to the workshop for examination.