Hi,

I have a problem with my central heating system, which I hope someone
could advise me on. I'm not very good with plumbing, so if I am lacking
info, please forgive me and ask for more details.

Anyway, My central heating pipes/rads make quite a lot of noise of
running water, particular upstairs and in the pipes going to upstairs.
The radiators upstairs are a nightmare. One of them is relatively ok,
heat-wise, but it needs bleeding every 2 or 3 days. The other radiators
are cold and appear to be empty. If I open the bleed valves on these
with the thermostat set so the pump and heating is running, then water
drains from the radiator (I can feel suction on the bleed valve.) If I
turn the thermostat so the heating is off, the radiators fill up, but
when they are full, they are still cold (getting full with cold water??)
Sometimes, through bleeding all rads at the same time and then switcing
the bleed valves off, I hear running water, then the header tank
overflow pipe starts spilling water. And that's about it, I'm not sure
where to begin to look.

Does anyone have any ideas or suggestions. I'm quite prepared to call a
plumber out if that's what's necessary, but I'd prefer to know what the
problem is before I did that so he can't try pulling the wool.

Many thanks for reading,
Bob

In an earlier contribution to this discussion,
Bob wrote:

Hi,

I have a problem with my central heating system, which I hope someone
could advise me on. I'm not very good with plumbing, so if I am
lacking info, please forgive me and ask for more details.

Anyway, My central heating pipes/rads make quite a lot of noise of
running water, particular upstairs and in the pipes going to upstairs.
The radiators upstairs are a nightmare. One of them is relatively ok,
heat-wise, but it needs bleeding every 2 or 3 days. The other
radiators are cold and appear to be empty. If I open the bleed valves
on these with the thermostat set so the pump and heating is running,
then water drains from the radiator (I can feel suction on the bleed
valve.) If I turn the thermostat so the heating is off, the radiators
fill up, but when they are full, they are still cold (getting full
with cold water??) Sometimes, through bleeding all rads at the same
time and then switcing the bleed valves off, I hear running water,
then the header tank overflow pipe starts spilling water. And that's
about it, I'm not sure where to begin to look.

Does anyone have any ideas or suggestions. I'm quite prepared to call
a plumber out if that's what's necessary, but I'd prefer to know what
the problem is before I did that so he can't try pulling the wool.

Many thanks for reading,
Bob

Has it ever worked? Has this problem arisen since someone did some
alterations or repairs to the system?

My first thoughts are that the pump is pumping in the wrong direction - and
needs turning round. But we really need more details of the system type.

Are both heating and hot water pumped, or is HW primary circulation by
gravity (convection)? Are there any motorised valves? If so how many, and
does each one have two or three water connections? [Photos of the pipework
in the airing cupboard - if that's where the valves/pump are - would be
useful].

Which header tank is overflowing - the large cold tank which feeds the
domestic hot water system, or the small tank for the heating system? If it's
the small one, is the ball valve working ok? What is the water level when
the system is cold? [There should be only 2 or 3 inches of water in the
tank - with the level a *long* way below the overflow to allow for
expansion].

That'll do for starters!
--
Cheers,
Set Square
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Set Square, thanks for your time and advice.


Set Square wrote:

Has it ever worked? Has this problem arisen since someone did some
alterations or repairs to the system?

It has worked much better in the past than it does now, although
problems seem to come and go. The upstairs rads have always needed
frequent bleeding, and the system has always been noisy, in terms of
running water. There hasn't been any work done, other than a boiler
service a year or so ago.



My first thoughts are that the pump is pumping in the wrong direction
- and
needs turning round. But we really need more details of the system
type.

Are both heating and hot water pumped, or is HW primary circulation
by
gravity (convection)? Are there any motorised valves? If so how many,
and
does each one have two or three water connections? [Photos of the
pipework
in the airing cupboard - if that's where the valves/pump are - would
be
useful].

My system consists of a Baxi Bermuda located behind my gas fire
downstairs. The pump is under the downstairs floorboards. I think (but
I'm not sure, sorry) that the HW is circulated by gravity. I really
couldn't answer about the motorised valve. I haven't noticed any around
the pump or in the airing cupboard, but this doesn't mean there aren't
any (it's generally inconvenient getting to the pump)



Which header tank is overflowing - the large cold tank which feeds
the
domestic hot water system, or the small tank for the heating system?
If it's
the small one, is the ball valve working ok? What is the water level
when
the system is cold? [There should be only 2 or 3 inches of water in
the
tank - with the level a *long* way below the overflow to allow for
expansion].

It's the small one that is slightly warm that sometimes overflows (but
hasn't done for some time.) The ball valve is fine, and the water level
is normally well below the outlet.)

I used to be able to bleed the radiators with the pump running in the
past, but like I said, if I do that at the moment, the rads appear to
drain. Where could the water be going? I haven't spotted a leak
anywhere (and I did look under the floorboards too


That'll do for starters!
--

I appreciate the help, if there's any more info I can give, I'll gladly
do so.
Many Thanks,
Bob.

In an earlier contribution to this discussion,
wrote:

Set Square, thanks for your time and advice.



My system consists of a Baxi Bermuda located behind my gas fire
downstairs. The pump is under the downstairs floorboards. I think (but
I'm not sure, sorry) that the HW is circulated by gravity. I really
couldn't answer about the motorised valve. I haven't noticed any
around the pump or in the airing cupboard, but this doesn't mean
there aren't any (it's generally inconvenient getting to the pump)

It's the small one that is slightly warm that sometimes overflows (but
hasn't done for some time.) The ball valve is fine, and the water
level is normally well below the outlet.)

I used to be able to bleed the radiators with the pump running in the
past, but like I said, if I do that at the moment, the rads appear to
drain. Where could the water be going? I haven't spotted a leak
anywhere (and I did look under the floorboards too

OK, it's almost certainly gravity HW circulation (two 1" or 28mm pipes
connected to one side of the boiler and going to the indirect coil in the
hot water cylinder in the airing cupboard) and pumped CH (two 3/4" or 22mm
pipes connected to the other side of the boiler). Presumably there's no
cylinder stat, and the DHW gets hot whenever either HW or CH are switched
on, and sometimes gets *too* hot?

I would guess from your further information that you have no corrosion
inhibitor in your system - with the result that a lot of sludge has built
up, partially (or even completely!) blocking some of the radiators. I would
also guess that what you are bleeding out is hydrogen caused by the
corrosion rather than air. [You can test for this by holding a lighted taper
in the stream of gas coming out of the bleed valve. If it burns, it's
hydrogen!]

Sludged-up radiators would probably explain what happens when you try to
bleed with the pump running. The pump is probably installed in the boiler
return - so that it's in effect sucking the water through the radiators. If
the inlet of a radiator is blocked, and you suck on the outlet with the
bleed valve open, you're going to suck the water out. This will end up in
the header tank, with a resulting rise in level.

It seems to me that your system needs a really good flush out, and then
needs to have inhibitor added. By far the best way to flush it out -
particularly with summer coming on - is to remove the rads and take them
outside and give then a good flush out with a hosepipe. While they're off,
flush the flow and return pipes by keeping the header tank full and opening
each radiator valve in turn (with a bowl under it to catch the water!).
Incidentally, take great care not to spill any black sludge from the
radiators on your carpets - it makes a pretty indellible dye!

If you get a plumber in, he'll probably want to charge you an arm and a leg
for doing a power flush. However, the method I have described is far
cheaper - and probably more effective.
--
Cheers,
Set Square
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Set Square wrote:
It seems to me that your system needs a really good flush out, and then
needs to have inhibitor added. By far the best way to flush it out -
particularly with summer coming on - is to remove the rads and take them
outside and give then a good flush out with a hosepipe. While they're off,
flush the flow and return pipes by keeping the header tank full and opening
each radiator valve in turn (with a bowl under it to catch the water!).
Incidentally, take great care not to spill any black sludge from the
radiators on your carpets - it makes a pretty indellible dye!

If you get a plumber in, he'll probably want to charge you an arm and a leg
for doing a power flush. However, the method I have described is far
cheaper - and probably more effective.

That's fantastic information, many thanks Set Square, I'll give that a
go. Incidentally, with me being a complete newbie, where does one put
the corrosion inhibitor? Does it simply pour into the header tank?

Thanks again,

Bob

Oops, using my brother's machine, hence the Steve!!

Bob

In an earlier contribution to this discussion,
Steve wrote:


That's fantastic information, many thanks Set Square, I'll give that a
go. Incidentally, with me being a complete newbie, where does one put
the corrosion inhibitor? Does it simply pour into the header tank?


Yes. After flushing it out, drain and re-fill the system. Part-way through
the fill process, pour in the inhibitor. It will then get thoroughly mixed
in.
--
Cheers,
Set Square
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Set Square wrote:

It seems to me that your system needs a really good flush out, and then
needs to have inhibitor added. By far the best way to flush it out -
particularly with summer coming on - is to remove the rads and take them
outside and give then a good flush out with a hosepipe. While they're off,
flush the flow and return pipes by keeping the header tank full and opening
each radiator valve in turn (with a bowl under it to catch the water!).
Incidentally, take great care not to spill any black sludge from the
radiators on your carpets - it makes a pretty indellible dye!

Hi Set Square,

Right, finally had a go at the first radiator....unfortunately the
results weren't as I was expecting from your description.

I took a rad off and flushed it out, and as expected was a bit mucky,
although not really sludgy. I then opened a valve on the pipes (not sure
which is flow and return, so did each separately.) Anyway, when the pump
was off, I got water flowing, which I let run until it ran clear.
However, when I switched the pump back on (by turning up thermostat) the
water stopped flowing and I could feel the suction at the valve again.
The same symptoms occurred at both valves. By the way, I closed the
valves on all other upstairs rads.

Is this what you would expect or is something else wrong. Additionally,
is there anything else I can try?

Many thanks for your assistance.
Bob

In an earlier contribution to this discussion,
Bob wrote:

Set Square wrote:

It seems to me that your system needs a really good flush out, and
then needs to have inhibitor added. By far the best way to flush it
out - particularly with summer coming on - is to remove the rads and
take them outside and give then a good flush out with a hosepipe.
While they're off, flush the flow and return pipes by keeping the
header tank full and opening each radiator valve in turn (with a
bowl under it to catch the water!). Incidentally, take great care
not to spill any black sludge from the radiators on your carpets -
it makes a pretty indellible dye!

Hi Set Square,

Right, finally had a go at the first radiator....unfortunately the
results weren't as I was expecting from your description.

I took a rad off and flushed it out, and as expected was a bit mucky,
although not really sludgy. I then opened a valve on the pipes (not
sure which is flow and return, so did each separately.) Anyway, when
the pump was off, I got water flowing, which I let run until it ran
clear. However, when I switched the pump back on (by turning up
thermostat) the water stopped flowing and I could feel the suction at
the valve again. The same symptoms occurred at both valves. By the
way, I closed the valves on all other upstairs rads.

Is this what you would expect or is something else wrong.
Additionally, is there anything else I can try?

Many thanks for your assistance.
Bob

Remind me of the original problem - it seems a long time since I wrote the
above!

A description of the system - including the relative position of boiler,
pump, zone valves, etc. would help. Even better if you can take some photos
and upload them to a website and post a reference to them.
--
Cheers,
Set Square
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