Flushing and treating Central Heating question


E

echo21

Hi,

I had a look at the FAQ and couldn't see the answer.

I have a conventional vented central heating system with a Potterton Prima B
boiler and a header tank in the loft.

The boiler is very noisy when heating the hot water for the cylinder, even
when the boiler is not lit and only pumping - is this kettling?

If so, will I need to flush and treat the system?

I am OK to do this apart from one small problem - I cannot find the drain
tap on any rads!
The only thing that looks like a drain tap is above the boiler on one of the
two pipes at the top labelled 'flow'

The other pipe at the top, I am assuming, is the return - there is a third
pipe at the bottom of the boiler which is the same width as the pipes going
to the rads - what is that?

If the tap on the flow pipe is the tap I need, how is it possible to get all
the sludge out of the rads which are lower than the boiler?

Thanks in advance for any help you can offer. :eek:)
 
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S

ski

Have you tried turning the pump setting down? There are usually 3 settings
on the pump. The noise may be from the pump being set on 3 instead of 1 or 2
 
D

David W.E. Roberts

echo21 said:
Hi,

I had a look at the FAQ and couldn't see the answer.

I have a conventional vented central heating system with a Potterton Prima B
boiler and a header tank in the loft.

The boiler is very noisy when heating the hot water for the cylinder, even
when the boiler is not lit and only pumping - is this kettling?

If so, will I need to flush and treat the system?

I am OK to do this apart from one small problem - I cannot find the drain
tap on any rads!
The only thing that looks like a drain tap is above the boiler on one of the
two pipes at the top labelled 'flow'

The other pipe at the top, I am assuming, is the return - there is a third
pipe at the bottom of the boiler which is the same width as the pipes going
to the rads - what is that?

If the tap on the flow pipe is the tap I need, how is it possible to get all
the sludge out of the rads which are lower than the boiler?

Thanks in advance for any help you can offer. :eek:)
(1) If this is kettling I assume it only happens for a short while after the
boiler stops firing? This would be due to the heat left in the boiler after
the flame was turned off, like a pan continuing to boil for a little on the
hob after you turn the gas off. 'Kettling' does in fact sound like a kettle
boiling. If you do have kettling you need to treat your system with Fernox
or similar, and flushing beforehand is a good idea. You can just treat,
however, by tying up the float valve in the header tank then slowly running
off some water by loosening a radiator connection over a bowl until the
header tank is empty. Then add your treatment and allow the system to
refill. You can also IIRC get treatment that can be injected directly into a
radiator through the bleed valve.

(2) There may be a drain on some pipework under the floor (if your pipework
does go under the floor). If not, you have a bit of a problem. You need to
have a drain tap to allow you to properly drain down.

There are various things you can try - I advise you to get a second opinion
though :)

(a) You can get the pros in to power flush your system - they can take a
radiator out to connect in their flushing system.

(b) If you turn off the taps each side of a radiator you can then ease off
the connectors, drain the radiator into a bowl, and remove the radiator. You
can then flush this radiator out with a hosepipe. If you can work out an
adaptor to fit a hosepipe in place of the radiator, you can then open the
radiator valve and drain your system. This is then a good time to cut into
your piping and fit a drain tap, (you will get a little wet) before
re-fitting the radiator. Alternatively you may be able to get a 'T' fitting
which connects in place of the normal radiator tap and has a drain tap on
it.

(c) You can get taps and connectors which can cut their way into full pipes
to form a 'T' junction. These are used for quick fit of outside taps and
washing machines or dishwashers. I don't know if there is a suitable one for
central heating and I have always wondered where the little bit of copper
went :) However if you can find such a fitting then you could fit a drain
tap.

(d) Get one of those 'freezing kits' and freeze your central heating piping
at the lowest accessible point. Cut out a piece and insert a drain tap
(compression joint would be easiest) before the pipe thaws again :) Make
sure you have enough play in the pipes to allow you to insert the
compression joint - if not, you will need a special 'expanding' one which
fits into a larger gap then adjusts to fit. You can then drain your system
whenever you want.


For A1 full effective flushing it is probably best to take all your
radiators off the walls and flush them out with a hosepipe. This is long
hard and laborious and prone to spillage of nasty black gunk inside the
house. However I have never been convinced that flushing compounds will
remove years of gunk from the radiators in a week. Our neighbour had his
system power flushed and says the difference was remarkable - however it
sounds as though his system was in a bad way before hand - radiators barely
heating etc.


HTH
Dave R
 
E

echo21

David said:
(1) If this is kettling I assume it only happens for a short while
after the boiler stops firing? This would be due to the heat left in
the boiler after the flame was turned off, like a pan continuing to
boil for a little on the hob after you turn the gas off. 'Kettling'
does in fact sound like a kettle boiling. If you do have kettling you
need to treat your system with Fernox or similar, and flushing
beforehand is a good idea. You can just treat, however, by tying up
the float valve in the header tank then slowly running off some water
by loosening a radiator connection over a bowl until the header tank
is empty. Then add your treatment and allow the system to refill. You
can also IIRC get treatment that can be injected directly into a
radiator through the bleed valve.

(2) There may be a drain on some pipework under the floor (if your
pipework does go under the floor). If not, you have a bit of a
problem. You need to have a drain tap to allow you to properly drain
down.

There are various things you can try - I advise you to get a second
opinion though :)

(a) You can get the pros in to power flush your system - they can
take a radiator out to connect in their flushing system.

(b) If you turn off the taps each side of a radiator you can then
ease off the connectors, drain the radiator into a bowl, and remove
the radiator. You can then flush this radiator out with a hosepipe.
If you can work out an adaptor to fit a hosepipe in place of the
radiator, you can then open the radiator valve and drain your system.
This is then a good time to cut into your piping and fit a drain tap,
(you will get a little wet) before re-fitting the radiator.
Alternatively you may be able to get a 'T' fitting which connects in
place of the normal radiator tap and has a drain tap on it.

(c) You can get taps and connectors which can cut their way into full
pipes to form a 'T' junction. These are used for quick fit of outside
taps and washing machines or dishwashers. I don't know if there is a
suitable one for central heating and I have always wondered where the
little bit of copper went :) However if you can find such a fitting
then you could fit a drain tap.

(d) Get one of those 'freezing kits' and freeze your central heating
piping at the lowest accessible point. Cut out a piece and insert a
drain tap (compression joint would be easiest) before the pipe thaws
again :) Make sure you have enough play in the pipes to allow you to
insert the compression joint - if not, you will need a special
'expanding' one which fits into a larger gap then adjusts to fit.
You can then drain your system whenever you want.


For A1 full effective flushing it is probably best to take all your
radiators off the walls and flush them out with a hosepipe. This is
long hard and laborious and prone to spillage of nasty black gunk
inside the house. However I have never been convinced that flushing
compounds will remove years of gunk from the radiators in a week. Our
neighbour had his system power flushed and says the difference was
remarkable - however it sounds as though his system was in a bad way
before hand - radiators barely heating etc.


HTH
Dave R

Thanks for such a good reply!

I should have said that the boiler is mostly noisy when it's heating the
water for the hot water - sorry.

I take it that flushing the system is the same whatever the problem?

So, what is that drain tap on the boiler for? would that suffice?
 
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A

Andy Hall

Thanks for such a good reply!

I should have said that the boiler is mostly noisy when it's heating the
water for the hot water - sorry.
This is likely to be because the coil in the HW cylinder is not
transferring anything close to the heat that the boiler is producing.

This can be because the coil is inadequately sized (as it can well be
in an older cylinder) or because it is furred up. It is also
possible that there is a gunging up within the primary side or perhaps
a problem with the motorised valve, although I think that's less
likely.

Does the boiler cycle on and off a lot when just heating the HW and
does the water take a long time to heat from cold?

If it isn't kettling and cycling a lot when running the heating, then
something going on at the cylinder is a likely culprit.

I take it that flushing the system is the same whatever the problem?
I think it's worth flushing the system anyway. You can get one of
the power flushing companies in to do the work but expect your wallet
to be £500 or more lighter when they have - this is frankly money for
old rope.

You can hire the equipment and chemicals and do it quite easily
yourself.

I found a better solution is to flush at each radiator position.
Basically this involves removing each radiator in turn and flushing
water out at each valve. This is better if you have a sealed system,
but I've done it fairly well with an open one as well. If you
Google in previous threads you will find I posted a step by step
instruction on this method.

After doing this, one of the chemical flushing agents run for a week
works quite well to mop up most other crud, then a final flushing is
done.

However, I have a feeling that the problem may have to do with the
cylinder coil. If it's furred up, the only way to tell for sure is
by inspection. This involves draining down the hot water system,
and the cylinder itself - there should be a drain cock near the bottom
of the cylinder on the cylinder itself or the cold feed pipe from the
roof tank.

You can then remove the immersion heater and look inside with a torch.

If you are in a hard water area and the coil has scaled up, if you
install a water softener (a proper ion-exchange one) the scale will
gradually dissolve over several months. However, the more realistic
fix is to replace the cylinder.


So, what is that drain tap on the boiler for? would that suffice?
That's to drain at the boiler. The problem is that it is often on a
direct path from the header tank in the roof so flushing through it
doesn't remove much gunk from the system.



..andy

To email, substitute .nospam with .gl
 

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