Was putting radiator back on wall, attached pipes, turned spindle to open valve back up and it snapped. Can't open the valve now. Gutted. It's the right-hand lockshield valve on the bathroom radiator (both vavles are lockshield valves). Part of a Combi system. Do I now have to drain the system before replacing the valve?

On Sat, 14 Jan 2006 20:00:17 +0000, The Count
wrote:


Was putting radiator back on wall, attached pipes, turned spindle to
open valve back up and it snapped. Can't open the valve now. Gutted.
It's the right-hand lockshield valve on the bathroom radiator (both
vavles are lockshield valves). Part of a Combi system. Do I now have
to drain the system before replacing the valve?

If it's a sealed system, then you would at least need to release the
pressure, but realistically, you would also need to partially drain
the system to below the level of the valves as well.



--

..andy

In an earlier contribution to this discussion,
The Count wrote:

Was putting radiator back on wall, attached pipes, turned spindle to
open valve back up and it snapped. Can't open the valve now. Gutted.
It's the right-hand lockshield valve on the bathroom radiator (both
vavles are lockshield valves). Part of a Combi system. Do I now have
to drain the system before replacing the valve?

If you can find another identical valve (apart from not being broken!) and
de-pressurise the system, you *may* be able to change it without draining
down - especially if the bathroom has a hard, wipeable, floor covering.

Put lots of old towels down to catch any spillage. Get the new valve ready
to fit - valve closed, and compression nut and olive removed. Keep the old
valve pressed down onto the olive, and unscrew the compression fitting nut.
Then whip the old valve off, and the new one on, and screw the (old)
compression nut onto the new valve. There will be *some* spillage, but the
open (unpressurised) pipe will only be exposed for a fraction of a second -
so you shouldn't spill much.
--
Cheers,
Set Square
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Set Square wrote:

There
will be *some* spillage, but the open (unpressurised) pipe will only
be exposed for a fraction of a second - so you shouldn't spill much.

An assistant with a wet vacuum would reduce that spilage to almost zero.
Why all plumbers don't carry a wet/dry vac is beyond me.

Dave

On Sun, 15 Jan 2006 02:37:38 GMT, "david lang"
wrote:

|Set Square wrote:
|
| There
| will be *some* spillage, but the open (unpressurised) pipe will only
| be exposed for a fraction of a second - so you shouldn't spill much.
|
|An assistant with a wet vacuum would reduce that spilage to almost zero.
|Why all plumbers don't carry a wet/dry vac is beyond me.

Evolution is taking a long time developing four hands?
--
Dave Fawthrop dave hyphenologist co uk
17,000 free e-books at Project Gutenberg! http://www.gutenberg.net
For Yorkshire Dialect go to www.hyphenologist.co.uk/songs/

Much appreciated. I'll try to find an identical valve. When you say de-pressurise the system, does that just mean turning the boiler off?

On Sun, 15 Jan 2006 09:16:17 +0000, The Count
wrote:



Much appreciated. I'll try to find an identical valve. When you say
de-pressurise the system, does that just mean turning the boiler off?


You certainly need to do that and also make sure that the pump is off,
so turn off gas and electricity.

We have both assumed that you have a sealed and pressurised CH system
because that is typical with combi boilers.

This means that you do not have a small header tank in the loft and
that somewhere - typically near the boiler - there is a filling loop.
This is a valve with threaded fitting and a non-return valve with
another valve connected to the cold mains. Between them goes a short
braided hose (which should be removed when not in use). On the
boiler, or somewhere on the system, there should be a pressure gauge.
You may also have separately, although typically it's inside the
boiler, a pressure vessel. This is a metal container with a
diaphragm with air or nitrogen behind it. When the system is filled,
this is compressed and maintains a pressure in the system as well as
handling the expansion of the water when heated.

If you have this, then dropping the pressure consists of hooking up a
hose or a container to a drain cock at a low point on the system. When
you open this, the pressure will release and push the water out. You
can then open a vent on the radiator in question and let the water
naturally flow out through the drain. With a container under the
union of the broken valve, you can open the union nut and check when
water stops coming out. At that point, you can close the drain cock.

If you have an open vented system, the procedure is to tie up the
float or otherwise turn off the water. Then proceed with the drain
cock as before.

Note that it is likely, if no corrosion inhibitor was used, that the
water will be discoloured yellow or black. This stains furnishings
indellibly so lots of protection and ability to mop up are called for.

If the water is black or there are signs of sludge, then it would be a
good opportunity to flush the system thoroughly by draining all the
way down and refilling a couple of times. If you have the sealed
system, refilling is simply a case of closing the drain and hooking up
the filling loop. Pressurise up to about 1.5bar on the gauge.
Once the water is reasonably clean (if it has been black), you can add
a flushing agent to the system and run it hot for a week, then flush
again.

Finally, add a corrosion inhibitor. You can use liquid ones with
sealed systems but it can be a fiddle. While you are plumbing, you
could put in an upward pointing short length of pipe in a convenient
place and then fit a stop end or a valve to it. Liquid chemicals can
be added with a funnel or by siphoning with a tube.

Alternatively, there are gel inhibitors and flushing agents that can
be injected using a mastic gun. The cartridge comes with a short tube
and a nozzle which goes into a radiator vent. They work well if you
ignore the manufacturer's procedure of trying to inject with the
system under pressure. Leaking or ****ing out is likely from the
nozzle. Injecting into a radiator while the system is empty and not
pressurised is much easier and cleaner.



--

..andy

In an earlier contribution to this discussion,
The Count wrote:



Much appreciated. I'll try to find an identical valve. When you say
de-pressurise the system, does that just mean turning the boiler off?

No - but it goes without saying that you don't run the boiler while you do
this! De-pressurising means letting some water out so that the pressure
gauge reads zero. You could do this by opening the valve which *does* work
on your bathroom rad, while the rad is off - and collecting a litre or two
of water in a container.

You will, of course, need to re-pressurise it via the filling loop when it
is all back together.

[If this doesn't make sense, maybe you shouldn't be doing any of it!]
--
Cheers,
Set Square
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Thanks Set Square. That does make sense. I'm fine with re-filling, but wasn't too familiar with draining. But your method sounds good. The reason I put about 'just' turning boiler off, is when I do the pressure seems to be at zero (since removing bathroom rad and it's contents)....but I suppose it must not be quite at zero, and 0.1 bar may cause problems?

Cheers

In an earlier contribution to this discussion,
The Count wrote:

Thanks Set Square. That does make sense. I'm fine with re-filling,
but wasn't too familiar with draining. But your method sounds good.
The reason I put about 'just' turning boiler off, is when I do the
pressure seems to be at zero (since removing bathroom rad and it's
contents)....but I suppose it must not be quite at zero, and 0.1 bar
may cause problems?

Cheers

You don't want *any* pressure in the system when you swap valves - otherwise
you're likely to end up with a flood.

Under normal circumstances, the system should be at about 1 bar when cold
(with the boiler not running) and about 2 bar when hot.
--
Cheers,
Set Square
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