no hot water at times how do i remove sludge from my boiler valliant 242 that is what engineer says

nitin, May 2011

drain the water system down,(at the drain off points) refill system via the filler loop then bleed and run it,repeat the drain down and refill it process, do this till the water comes out clear when satisfied add a rust/sludge additive and then refill the system

wirecutterman, May 2011