central heating - sludge

AHarvey

AHarvey

AHarvey

Soldato
Joined
6 Mar 2008
Posts
10,092
Location
Stoke area
Hi all

Since we've moved in 9 years ago Worcester boiler has been playing up. It can goes months where it's fine, then it'll need resetting constantly to get hot water.

We've had services done etc and had a switch replaced but we've had a few comments about black sludge being in the system and it needs flushing out. I'm sure one engineer fitted a filter to stop it tripping the boiler but it's started doing it again.

So, before the weather turns, it's a job that needs doing and i've been told I can do it myself.

It's a closed system, 2 floors and 7 radiators in total.

Never done it before so educate me, what do I need and how do I do it? Any links to online resources.
 
Drain the system, it should have a lowest point drain valve. Remove each radiator carefully as you don't want any liquid on your carpet, take it outside and poke a hole in the inlet valve nd blast it full of water. Keep going until water comes out clean.

Re attach and pump the system back up bleeding each radiator as you go.
 
He needs to hire a powerflushing machine and know how to use it properly which I'm guessing the op doesn't

So therefore hes better off getting it done properly
 
Well it seems that the system has a Spirotech filter attached, taken 20 pints of water out and there's just a few little black bits in it, videos say is should be dark dirty water but this is just a little misty.

Looked at Powerflushing systems and quotes seem to be £400+, thinking it may be cheaper to have my mate buy and fit double radiators instead of the single panel ones we've got.
 
Is it just hot water it overheats on?

If so its probably the plate heat exchanger scaled.

Does the water struggle to get piping hot
 
I'd probably flush each radiator out seperately first, then running Fernox F3 cleaner in the system for a week. Flush the system again then put Fernox F1 inhibitor in.
 
The_One said:
Is it just hot water it overheats on?

If so its probably the plate heat exchanger scaled.

Does the water struggle to get piping hot
Click to expand...

Heating as well as the water, and the water does get piping hot.

It's just turn water on, have to reset it, works fine. Heating comes on, have to reset it, works fine.

Randomly goes off now and then too. It's been this way for since we moved in, British Gas have replaced bits etc over the years but it's never solved the issues. It can go months and it's fine, then it happens over and over again, then stops again.
 
I would drain it, run it, drain it, run till its pretty clear then add to the header tank before it fills back up x100 and x200. I got another 5 years out of a noisy overheating old boiler with that.
 
We had a new boiler fitted year before last, and requested that it was power flushed as some rads had cold spots at the bottom, plus it was a 40 year old back boiler being replaced which hadn't been serviced in forever. Amazingly he said there was no sludge in the system at all though and the rads have been perfect since, didn't cause any leaks or anything.
 
The_One said:
^thats not a proper job

and wont affect the boiler overheating
Click to expand...

Correct not a proper job but it works, radiators are most likely places for sludge to build up, flushing them outside the house means there is no chance of residual buildup in other parts of the system.

I've done it this way for years, (every 2 years) as it's the way my dad and grandad have taught me. British gas engineer (a personal friend) said our system for its age is the cleanest he has seen in years!
 
Power flushing, is a very useful tool, but also overrated. You are limited by the system design, pipework size, and radiator valves.

If your want to do a 'proper' job, then get a filter fitted, put cleaner in the system (type will depend on severity of sludge/sediment) then once the cleaner has done it's job remove all the radiators and wash then out with a hose pipe, use two people to wash and swill them thoroughly, clean the filter then add sufficient inhibitor.
Once that is done and you still have boiler issues then you need to go through the process of chemically cleaning the boiler with some serious chemical or replacing parts. Whichever is required due to the specific fault you are experiencing, not a diy job tho.
 
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