Isolate the hot and cold 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. Remove the cold side strainer and check valve cartridge using a 12mm hex key. Insert the Optitherm's flushing adaptor into the void and tighten using an 8mm hex key. Attach the hose to the adaptor, making sure the open end hangs down into the basin or bath. Open the cold supply at the spigot. Expect a large surge of water that, due to its higher velocity, scours biofilm from the inside surfaces of the pipework and removes it to drain. When the water runs clear close the cold supply isolating valve. Remove the flushing adaptor and replace the strainer/check valve cartridge. Repeat this process for the hot water supply, taking care to avoid scalding. Replace the strainer/check valve cartrdge then replace the tap's bottom cover using a strap wrench. Reopen the hot and cold water supplies.