Should there ever be a need to drain down your central heating system below is a guide how to do it. Abbey Wood Plumbers are experienced in draining down in such systems. Ensure the power supply to the central heating system is turned off.If it is a vented system you must now turn off the isolation valve which supplies the system. This will not apply for a sealed heating system because there is no permanent water connection. The isolation valve for the vented system can be found on the inlet supply pipe to the feed and expansion cistern, located in the loft. You are now ready to start draining down.Locate a drain off cock at a low point in the system, usually situated near the boiler itself. Connect the hose and open the valve. Next find a radiator high in the system and open the air release valve with a radiator key. This assists the process of draining down by letting air into the system, you should hear the air rushing into the system as a water leaves.Slowly open more radiator and events ensuring to do the higher-level radiators first until they are all open.When all of the water has been removed it is wise to close the radiator owners to ensure the system is ready to refill and to make sure the valves, if fully removed, are not lost.Sometimes the drain off Cock can fail to open because the washer is stuck onto the seating. If so it is a good idea to try and locate another valve.Note:The water that has drained from heating system can be just like black ink can cause staining just the same so protect you carpet. If you do not feel confident to carry out this job which is quite time-consuming and can cause problems it done wrongly, you should seek professional advice from someone like a Thamesmead plumber.