This summer we moved into 4 bed, 1 bathroom, 1 shower room house. As
we were about to renovate the place we decided to get the heating
system updated. We got the details of a local plumber who had the
necessary unvented heating certificate from the Institute of Plumbing.
He installed a 210lL unvented cylinder, a Potterton Surpima 100
boiler, replaced all the 9 radiators, and desclaed the system. We
advised him at the time that we may convert the loft at some point and
so needed some spare capacity in the system. We paid him over £6k for
We have 2 problems.
The first is a knocking noise in the floor of the bathroom and the
bedroom closest to the bathroom. Not a loud banging but enough to
wake up anyone sleeping in there. It doesn't happen the whole time
the heating is on but isn't just when it's warming up. From reading
this forum, it seems one possible soultion could be that the pipes
aren't clipped down. If I get someone in to lift the floorboards will
it be obvious how and where to clip down the pipes? (DIY novice
The second problem is that the rad at the end of the system (our
bedroom) doesn't get hot if all the other rads are on. I believe this
could be the pump size or boiler size. What size pump should I have?
The boiler is on the ground floor and the rad on the 2nd floor.
We've asked our IoP registered, corgi plumber back but he's claiming
it's nothing to do with him. He says the knocking is from the old
system and the rad doesn't heat up because of the pipe size or maybe
sludge in the system. He never mentioned pipe size when he was
fitting our boiler, rads and cylinder. And as replaced all rads and
rescaled the system I wouldn't expect any sludge.
Any advice much appreciated.
Loose pipes should be fairly obvious if you lift the floorboards. Pipes do
need to move a bit when they warm up and cool down, so it doesn't do an harm
to put some felt or other soft material under the pipes where they pass over
joists to help them to slide quietly.
Does the end radiator *ever* get hot - like if you turn other radiators off?
If so, it sounds like the system simply needs to be balanced - which means
restricting the flow to the hotest radiators to share out the heat evenly.
There is a scientific way of doing this - which involves making numerous
temperature measurements on the flow and return pipes of each radiator.
There is also a "seat of the pants" way - which simply involves determining
which radiators are hottest (by touch) and turning down the lockshield
valves on those in order to force more water through the cooler radiators.
I would be very surprised if either your boiler or pump are inadequate -
it's almost certainly just a mattter of setting it up properly.
Did he make any recommendations - like replacing the pipework - at the
time of giving his estimate?
If not, since he changed the rads, it's not unreasonable to expect them
*all* to work.
Sounds like the threat of a small claims court might get him off his a**e.
However, two things are likely.
One is an airlock. Have you tried bleeding the rad to make sure there's no
air in there? If water doesn't immediately come out under pressure and
there's no air either it could well be an airlock.
Next, as has been said, is balancing the system. If you turn off all the
other rads and this one now works, then this is probably the cure. See FAQ
for details of how.
*I get enough exercise just pushing my luck.
Dave Plowman email@example.com London SW 12
Thank you for your replies.
In answer to your questions:
He never mentioned the pipes when quoting or installing the radiators.
The end radiator does get very hot if all the other radiators are
turned down to half heat. Does the balancing result in being able to
have all the radiators on full? I was kind of hoping to be able to
heat the whole house at once!
I will certianly report this guy to the IoP. He is pretty aggressive
when we try and talk to him about these problems and keeps saying it
must be a problem with the old system, when he's changed everything
except the pipes.
I assume that padding the pipes is relatively simple so I think we'll
give that a try. Any words of wisdom about the best way to lift the
floor boards (not tongue and groove) and which padding to use?
Thank you again
On 10 Dec 2003 08:42:24 -0800, firstname.lastname@example.org
Yes, that's the whole point. The radiators that are nearer to the
boiler and pump will tend to get a greater flow of water because the
pipe runs are shorter, all else being equal.
The lockshield valves are there to reduce the flow through radiators
that have a lower flow resistance through being on shorter pipe runs.
Essentially, balancing will reduce the flow through those and the pump
will then tend to push more water around the further radiators.
In fact balancing is really done on temperatures rather than flows
because most systems have radiators of different sizes. It happens
that the amount of heat transferred is directly proportional to the
flow rate, so actually a larger radiator needs more flow than a small
one anyway. Therefore the way that balancing is done is to make the
temperature drop across each radiator equal to the others. It's a
bit of a lengthy process to do, although not difficult, because
adjusting a radiator's lockshield valve (the preset one that you don't
turn) will have an impact on the others. Therefore you have to go
round the house several times adjusting and measuring the temperatures
of the radiators. To some extent, once they are all heating, and
the rooms are getting warm, then some people call it a day. You can
be as much of a perfectionist as you like past this point.
It is a pretty easy job to do using either a clip on boiler
thermometer or a hand held infra red thermometer costing about £30.
Now why am I surprised. He's charged you a lot of money, to be
honest and it's unacceptable that he is walking away from making the
system work properly.
Obviously you *could* pursue him through Trading Standards or the
courts as well, however the value of the work that needs doing is not
high and is easily do-able yourself. So it's up to you whether you
want to make a stand on principle beyond reporting to the IoP or
whether to just chalk it up to experience and move on.
If you look carefully, almost certainly specific floorboards will have
been up before to put in the pipes in the first place. The boards may
even be screwed rather than nailed down. Since it isn't T&G this
makes life a lot easier.
You really need a wide levering object to lever the boards up
carefully. Something like a wide brick bolster is commonly used
just by hand.
but you can get them in any tool store or DIY place.
For the insulation, I've generally used flat felt type lagging, which
can be wrapped and taped around the pipes at the joists.
www.bes.ltd.uk and search on 12658. You should be able to get it
from heating or plumbing merchants as well. The foam tubular stuff
is a bit large for this application.
It goes without saying that care is needed not to nail or drill
through pipes when refitting boards.
Actually, its even easier than that, if you are living in the house.
First of all, check that any 'cold' radiioators are fully open both on
teh control valve (the one with the knob) and the lockshields (the one
that needs a pair of pliers to turn it on.
Fire up teh heating system and have a cup of coffee and a gossip with
the neighbours, till the rooms are more or less warm/hot etc.
Now take the hottest room, and turn the lockshileds off completely, then
turn em on a little bit.
Repaet coffee gossip, and cheack again, turning off all ultra hot room
lockshields, then on a little bit.
Sooner or later the cold rads warm up, and you can just fine tine the
bloody lot a little at a time.takes a week or two, but you have the
Alternatively, fit TRV's to the hottest rooms and let nature take its
Yeah. So what? at least it comes on eventually...When I had TRV's fitted
I just opened up all the balance valves. Basically because the ones nea
the boiler where the ones I wanted to get hot quickly
anyway...eventually the remote bedroom ones would come on...
Well, in my case, it's the kitchen that comes on last as it's the furthest
one from the boiler, pipe run wise. And that's probably the second room
you visit first thing...
I can't quite follow your reasoning. A well balanced system can do without
TRVs altogether. Adding them to one which is, is merely the icing on the
cake. Using them to cure an unbalanced system is a bodge and serves no
purpose, given that anyone can balance up a system given the inclination.
*If at first you don't succeed, redefine success.
Dave Plowman email@example.com London SW 12
Its very hard to balance a large house with any rads. I gave up and
fitted TRV's everywhere except the bathroom, and unbalanced the lot, and
turned the stat to max.
Worked extremely well until I pulled the whole house down :-)
This allowed me precise control of every room - something you can't do
easily with a straight 'turn it on a bit' type regulator, and a red hot
bathroom, which is fine by me :-)
Its obviously better to fit stats in every room and zone valves and AND
the valve outputs back to the pump...but frankly as an improvement on an
old rired system, TRV's and whack up teh stat works, is cheap, and who
cares if some rads hog everything till the rooms are warm?
If you do care, balance as well.
Well quite. Sometimes one also wants the system unbalanced (sunny day in
room with lots of glass, lots of people in a small room suddenly, open fire
in the winter etc. ). It's a lot easier with TRV's. (IMHO of course).
(anti-spam is as easy as 1-2-3 - not)
Yes - the radiators give their stated output without water being pumped
through them at a 'maximum' speed. Reducing the flow slightly to most will
make no practical difference to them, but a great deal to the one which
If you have a go at this yourself, the lockshield valves don't have the
same 'law' as a tap - you have to turn them near off before anything
happens, and then it all happens at once.
If you haven't got a suitable thermometer for measuring the pipe
temperatures, a trip to Ebay (Test Equipment) will find a DMM (digital
multi-meter) on offer there which as well as volts etc will also measure
temperature rather more accurately than the cheap dial thermometers you
can get in the sheds. Should cost no more than about 20 quid, and will
find plenty of other uses in the home.
*I'm already visualizing the duct tape over your mouth
Dave Plowman firstname.lastname@example.org London SW 12
On 10 Dec 2003 01:53:10 -0800, email@example.com
Without hearing, it's a bit difficult to tell, but from your
description sounds like it is from the pipes expanding but being
trapped in some way, usually in the joist notches or holes through
which the pipes pass. This is avoided by wrapping some insulation
at each position so that the pipe can slide.
This is most likely because the system is not balanced, but could be
sludging or an air lock. If all the others are OK, then try turning
them all off bar the bedroom one and see if it heats up. If it does,
evenly and without a cool patch in the centre at the bottom then it is
most likely a balancing issue. There is a procedure in the FAQ to
this NG to balance radiators. Not difficult but a little time
He should certainly have cleaned the system when fitting a new boiler
anyway, and although a complete and accurate balancing exercise is
time consuming, he should have at least adjusted the radiator
lockshield valves sufficiently that all the radiators work. It is
possible, but unlikely that the pipe size is too small, assuming that
it worked before the boiler was changed.
On a reasonableness basis, he should have dealt with all of the above,
especially considering what he charged. On the noise from the
bathroom floor, I would say not unless he installed new pipework where
the noise is coming from. However, it is a pretty easy job to fix
once you can precisely identify the location.
What no-one else has meantioned/asked is whether the plumber fitted
proper TRV valves on the radiators and fitted a room stat. Since this
is a new system then building regulations do require him to do this.
Are you sure that the knocking is related to the heating ? Cos I've
had intermittent knocking which was specific to a single radiator and
was easily fixed by replacing a new but presumably defective TRV, and
I've also had extremely loud knocking which was caused by the toilet
cistern being fed directly from the cold water main (rather than from
a tank). The water was quite high pressure and used to jet out of the
valve quite hard, so much so that the float used to bounce as a
result. This would set up an oscillation, whereby the float would
bounce, let in more water, which would cause the float to bounce, etc
etc etc. Doesn't sound like much, except the shock waves ran right
through the cold water piping and the noise was terrible. It took me a
long time to realise that flushing the toilet was the cause, as it
would happen when the cistern had almost refilled, i.e. when it
'seemed' no water was being drawn. Drawing cold water off at a tap
when the banging started settled it down temporarily, and a permanent
fix/bodge was made by suspending a damping device from the float arm
(cable tie and a plastic beaker) within the cistern below water level
to make it less susceptible to vibrations.
Hope this helps.
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