DIY Doctor UK DIY Forums

Background: Combi boiler central heating system, 7 years old, regularly serviced under contract.

We have been advised during a regular service visit that our central heating system needs a "Power flush" - a mere £670. This includes a filter that will ensure that future sludge is dealt with as it forms. We will be required to remove the filter periodically and clean/ replace to prevent future build up of sludge. It appears that the "Power flush" takes up to a day to complete and the filter unit costs around £150 to £200.

An simpler (cheaper?) alternative that has been suggested. Install some form of magnetic strip in one of the central heating pipes. The magnetic unit has a shut off valve at either end and we would need to open it periodically and clean off the gathering sludge.

Does anyone have experience of this magnetic strip idea? Any idea what the unit is called and where you get it from? And, finally - what is a fair price for it?

Any advice or guidance would be mucgh appreciated.[/b]

Are you having problems with the system that would make you think you need any type of flush. If not then they're probably just after quick cash - alot of companies push for people to have sytems flushed that don't need it.

To prevent sludge/debri build up, you need to drain the sytem and check the water for sludge etc then refill the system adding a cleanser/descaler this needs to stay in the system for a few days (or as stated on bottle) then draining then refill adding inhibitor.

You can also install a Magnaclean or a Fernox Boiler buddy in conjunction with adding an inhibitor such as Fernox MB1 or Sentinel X100.

if your system is only 7 years old and serviced regularly i would have words if it is the same company because from installation it should have been treated on commisioning and a sticker stating when it needs doing again it is very very unlikely you need a power flush and sometimes these can cause more damage to the boiler as it can and has cracked the heater matrix in boilers ok here goes:

drain down your system disconnect the flow and return from the boiler you do not need gas certification for this squirt some fairy liquid in the flow and the return attach a hosepipe to the flow from the mains open up all your rad valves both sides attach a hose to the return and stick it outside turn on your tap and flush this will not damage your boiler run this for 1 hour and connect back up introduce fernox inhibitor and refill the system bleed and balance if you wanted to do a power flush just use a central heating pump and circulate between the flow and return then flush out

Thanks to the Heating Doctor and to the htg engineer for this information.

In response to the question by the htg engineer:

We were informed that there was a build up in sludge when the boiler broke down. The gas fired boiler would neither fire up when we turned on the hot tap nor would it fire up when the central heating came on.

The engineer came out, took the boiler apart and said that he found sludge in one of the valves which he cleared and re-assembled the unit. He recommended a Power Flush and some sort of filter connected into the system.

Apart from this one recent incident with a boiler malfunction we are fully satisfied with the system - the hot water is hot and the radiators are all functioning - hot across the entire panel.

I would add the cleanser as I have said in my last post, as this is what it is made and sold for. Leave in for the recommended time, as for the fairy liquid use this to wash your dishes as this is what it is made and sold for.

this is all fernox is check with your local chemist

OK thanks folks.

We have started stage 1 - introduced a Fernox concentrated "de-sludger" to the smallest radiator. It says on the bottle to leave for up to 1 week.

Next weekend we will drain the system - refill it adding a Fernox sludge inhibitor.

Total cost to date: £40 for two Fernox products plus a few hours of our time and the cost of a trip to the nearest supplier instead of the £670 estimate for the Power Flush and other stuff.

My wife is now wondering what to spend the £630 we saved on!!!!