How do I re-pressurise my heating system using the external filling loop?

Unscrew the blanking cap and attach the hose to the valve. Ensure both ends of the hose are hand-tight and the system fill isolation valves are closed (handle across the valve). Turn the handles through 90° to open the valves and slowly fill the system to between 1 and 1.5 bar, watching the pressure gauge. Turn the handles back through 90° to close the valves, then remove the hose and replace the blanking cap. Do not forget to disconnect the external filling loop after re-pressurisation to comply with Water Authority regulations.