Your warranty will be void if your new boiler becomes damaged because of sludge from your system. To prevent this the system must be flushed, it’s also advisable to get a central heating filter installed which will help combat sludge build up for as long as its installed. I recommend MagnaClean Professional they fit inline on the boiler return pipe.
Water pressure. Every combi boiler needs a minimum cold water flow rate requirement, it is vital that this is tested prior to the new boiler being installed
How long will it take?
An average combi to combi exchange will take 6-10 hours (normally done in one day) a conversion (system boiler to combi) would normally take 2-3 days, so be prepared for at least one night without hot water or heating if getting a conversion
How much will it cost?
The question everybody wants to know, as a rough guide a combi – combi exchange will cost between £1600 and £2600(inc vat) depending on size and type of boiler a conversion will be between £2200 and £3500(inc vat) this is a guide for London companies if you live in the north of the country then you can probably find it a little cheaper.