When the central heating system is going to be replaced by a new boiler installation, a good idea and the best thing to do, before this takes place is to carry out a full system clean, which will include the complete cleaning of the pipework. The process will make sure that the newly fitted boiler will pump the water through nice newly cleaned pipework. Corrosion in any system will be the result of debris left inside. This will damage pumps and the various valves also. Woodford Plumbers carry out this work as standard everyday. There will be a need to protect the central heating pump during the cleaning process, so it will be necessary to take it from the circuit. The integrity of the pipework can be maintained by using some hose to fill the gap left by the pump. The flush gear will be connected here if that is going to happen. It is recommended that a complete descaling and cleansing routine can be carried out if your system is old or badly corroded. Using very strong cleaners may uncover minor leaks that have been sealed off by all the corrosion in the pipes, so use a mild cleanser instead. This is a better option. The cleaner should be released into the system from the feed-and expansion tank or even into a radiator through its bleed valve. When this has been done you should make sure that the pump impeller turns freely. There will be some resistance but it should be relatively free and you can do this with a screwdriver. Of course at any time if you are not confident, call a professional plumber like a Woodford Plumber for a professional service. Take Note: If you hear loud hissing or banging noises from the boiler, a descaler treatment will sort this.