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?
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.
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
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
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.
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?
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.
Using Ubuntu Linux
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?
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
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?
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
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
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
I also drained/flushed every downstairs radiator individually as a last
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.
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 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?
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.