Flush out your heating system

DavidCH

My gas central heating system was gradually slowing up towards the end of last winter, and the boiler was "kettling" indicating the need for descaling. The system is the open vented type with a small feed /expansion cistern in the loft. The hot water storage cylinder is heated by an internal copper tube coil (so-called "indirect" type).
I drained the system, flushed it thoroughly, and when refilling, added a chemical descaler (Fernox DS40) recommended by my local plumber. The overnight improvement was far beyond what I'd expected. Next day I added the neutraliser powder and thoroughly flushed the system again. When refilling the system finally, I added a bottle of corrosion inhibitor which will protect the system for at least a year. I spent around £50 on the chemicals and two days repeatedly draining and refilling. British Gas wanted £500 for a powerflush which I'm sure was not needed.
Hot water recovery time is now halved from cold, and the radiators are much hotter. The boiler is almost silent in operation, like new. At the very least, I would advise anyone who has a system over five years old to ensure that it is at least flushed with a cleanser or descaled periodically and checked over by a specialist if necessary.

macman

Good result. BG typically charge twice as much for a powerflush as an independent, so there's never a need to pay that much.

Dangle

I flushed our central heating during the winter, not the best time of year to do it, but we had a recurrence of a boiler overheat problem when the central heating switched off due to a blockage in the bypass valve, and didn't want it happening again.


I removed a downstairs rad and connected hosepipes to both radiator valves, turned off the boiler, and shut the valves on all of the radiators, bypass valve and the stopcocks to isolate the heating loop feed to the hot water cylinder.

I then went round turning just one radiator on at a time, and fed water at mains pressure from one of the hoses around the system and out to a drain, giving the radiator a good banging to agitate the sediment so that it dislodged and got washed out the system by the water. Then finally, flushed the removed radiator outside in the cold before refitting it.



I the added a cleaning chemical and left it in for about a week, as recommend and then repeated the same process - didn't get much sediment out the second time, so my first attempt mush have been effective.



We also had a blocked air separator removed earlier in the year, which had been causing some hot water to flow up the expansion tube into the central heating fill tank, which can be quite dangerous if it was a plastic one (ours is asbestos). So do remember to put fresh inhibitor in regularly - I think ours hadn't been done for over 8 years.