Is powerflushing likely to solve my C/H problems?

I live in a small terraced house, and the central heating system consists of just six radiators (4 upstairs and 2 down). The pipes to the radiators are 10 mm plastic microbore with valves at each end of the radiators. The boiler itself is a Worcester Greenstar Combi installed by a small local firm in 2003; I'm not sure how old the radiator system is, but I would guess about 12 years - it was already in the house when I bought it in 2000 - the pipework looks a bit amateurish to me but otherwise its been OK up till now.
My problem is that 3 of the six radiators have stopped heating properly - they only get warm to the touch even though the TRVs are fully open (they're not stuck by the way). It started last summer with the two downstairs and now recently one of the upstairs radiators has stopped working as well (this seemed to happen in a day or two). They're all slightly warmer at the top than the bottom as one might expect, but otherwise they don't seem to have any noticeable hot or cold spots.
I had someone from the firm who installed the boiler to look at it. He said that powerflushing would cost around £400 but didn't seem at all sure that it would actually work very well with microbore pipes. He suggested taking the offending radiators out off at a time and flushing them out with a hosepipe as a first step. But given that the latest radiator to fail stopped functioning quite quickly, it doesn't seem to indicate a slow build-up of sludge as he seemed to think.
Given that I'm not competent to do this or any plumbing work myself, I'm rather reluctant to get people out to fiddle around with half measures that may not solve the problem. What would the experts advise?
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Mike Lane
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Take the advice given by the person you called - or call a plumber. Powerflushing at £400? cowboys or what/.
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R Gower wrote on Dec 13, 2009:

[OP snipped]

What would be a reasonable price? Is it likely to work?
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I would think taking them off - one at a time (or getting it done) to clean them would be a good starting point and a good thing to do anyway. Whilst off - check the flow from each radiator valve - into tray - hose or something. This will flush the pipe and let you see the flow rate.
Have you tried a heavy duty system cleaner? Then do above job.
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Mike Lane wrote:

I did this last year and everything's been fine ever since. I took of each downstairs radiator (with a freind) and we took them into the back garden and flushed them through with the hosepipe, each one took about 15 mins, from coming off to going back on. Then I filled the system and allowed it to heat up to full temperature for an hour, then drained the system again, but this time, just through a drain with a hose attached, while the system was draining, I opened the filling loop so that it was filling as it emptied, so as to rinse it through, and also went around the house opening and closing valves at random, forcing the water to take different routes. When I was satisfied that it was as clear as I was going to get it, I disconnected the drain and filled the system again, but added a sludge remover and fired up the system and allowed it to circulate for 3 - 4 days, then simply drained it and refilled with clean water and inhibitor.
You say you aren't competent enough to do it, but it's just a matter of turning off the valves at each end of the radiator and removing the nuts, making sure you put your finger over the hole in the rad as you take the nut off - if you have a large cloth it would be handy to catch any drips as you get your finger in place, then it's just a matter of lifting and carrying outdoors for flushing - do it from both ends, and also, give it a shake about when half full - a radiator is nothing more than a flat metal bottle
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Phil L wrote on Dec 13, 2009:

Yes well I know it sounds a bit wimpish to say I can't do it myself, but I think in this case it's true. The radiators themselves are quite large and filled with water will weigh a lot. My background is in electronics and I have an innate fear of anything to do with pipes and water! However I take your point and I'll probably get someone in to do it for me. Thanks for the suggestion.
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Mike Lane
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In an earlier contribution to this discussion,

No-one in his right mind would try to carry a radiator full of water - especially by just keeping the water in with your thumbs! That is a recipe for plastering your carpets with indelible black gunge - quite apart from the likely hernia. You need to drain it first!
I'm afraid that the previous poster is talking out of his nether orifice - he's obviously never tried to follow his own instructions - otherwise he would know better.
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Roger
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Roger Mills wrote on Dec 13, 2009:

Yes, well these are the kind of problems I don't have the knowledge or expertise to deal with myself.
However I wish that someone could answer my original question i.e. would the so-called power-flushing process be likely to work with microbore piping, and is it a sensible solution to the problem?
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Mike Lane
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On Sun, 13 Dec 2009 23:18:19 +0000, Mike Lane wrote:

=============================================== Yes, power flushing will work but you can save yourself a lot of money by trying the method I suggested in my earlier reply. Even if you don't want to remove the radiators you might still restore the flow sufficiently to complete the job with a good chemical flush.
Cic.
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YAPH wrote on Dec 14, 2009:

Thanks for your reply. Yes, it occurred to me that it could be the pump since the radiators seem to be failing one by one, and it happens quite quickly (the one upstairs was working fine until a week ago when it stopped getting hot). However the hot water is quite OK. Does it really use the same pump? It's a plain combi system with no separate water tank.

That does make good sense - I've already decided to get a second opinion from another plumber who seems very competent (unfortunately he's on holiday at the moment) and see what he comes up with. Presumably there are ways to test if the pump is working properly?
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On Mon, 14 Dec 2009 14:31:00 +0000, Mike Lane wrote:

Not all combis do but Worcester Greenstars do.

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YAPH wrote on Dec 14, 2009:

OK, well that seems to rule out a failing pump as a possibility, which leaves the question of why the system has become blocked up (if that's what's happened) in a relatively short time.
The boiler itself was definitely installed in February 2003 which makes it nearly 7 years old. According to the check list left by the installers, the system was "flushed in accordance with the boiler manufacturer's intructions" with a cleanser described as "Sentinel x 400" and an inhibitor "Sentinel x 100" being used. Of course this job might have been skimped - I've no way of telling.
Is there anything else in the system I should check (or get checked) before I ask someone to start removing and flushing out the radiators?
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Mike Lane
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On Tue, 15 Dec 2009 12:42:01 +0000, Mike Lane wrote:

Another item which could affect CH circulation is the motorised diverter valve which redirects hot water from the gas->water heat exchanger, which by default goes through the PHE to heat DHW, to the CH. If this valve isn't opening properly you'd get poor circulation through the CH system
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YAPH wrote on Dec 15, 2009:

That seems like a possibility. I'll mention it to whoever I get to sort out the system. Thanks.
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Mike Lane
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I power flushed my system (8mm microbore) by hiring the power flusher for GBP45.00 (weekend rate) back in 2003. It came complete with a box of sludge remover which was charged on the basis of how many bottles were used.
The only problem was getting the CH pump off (the flusher replaces the pump). Other than that I was able to flush the whole system, forwards and backwards to my heart's content until the water ran clear as a mountain stream compared with the coal black sludge that came out when I started.
I also drained/flushed every downstairs radiator individually as a last resort..
I had the boiler replaced shortly after this and noted that the plumber hadn't added any inhibitor to the system. He apologised and tipped a bottle into the header tank! Needless to say, I drained the system enough to get it into the pipes as it was unlikely to get there on its own for some time.
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Frank Spencer

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Frank Spencer wrote on Dec 18, 2009:

Thanks - that's useful to know. I'll probably first try flushing out the radiators and pipes separately as has been suggested. If that doesn't work the power flusher might be a last resort.
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Why would a combi have a pump for the hot water?
MBQ
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wrote:

Why would a combi have a pump for the hot water?
The pump is not for the hot water but to circulate the primary hot water round the heat exchanger. This then heats the mains water which comes out of the tap.
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On Tue, 15 Dec 2009 20:14:43 -0000, "Heliotrope Smith"

The W-B boilers with thermal stores built in use the pump for the hot water.
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wrote:

pump
quite
really
of
The only one that springs to mind is the Hiflow 400 which has a heat bank of around 50-60 litres. This still uses the pump/circulator to heat the cold mains water through the plate heat exchanger.
Which model/s are you referring to?
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