"echo21" wrote in message
...
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. )

(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