Removing a central heating radiator. Combi Boiler

[davidk65]

I have to remove a radiator for repairs/renewal. The radiator is heated by a Combi boiler. At one end of the rad is a thermo valve and the other is a lock shield valve. I have removed the head of the thermo valve and used the supplied plastic cover to shut this valve off. The problem is the lock shield valve. To close this valve I have to use a flat bladed screw driver, however, when I do this turning from open to close water starts to dribble out of the valve opening. At this stage I am not sure if the valve has closed but water is obviously bypassing the valve spindle. The other thing that puzzles me I expected the leaking water to be black but it is clear in colour
I assume the valve is faulty and I will have to be replaced? The question is how do I go about draining own the heating system to replace or attempt to repair the valve? Bearing in mind that I need to keep the hot water side of things.
I cant see any valves on the boiler but at this stage I have not taken any panels of the boiler.
Any suggestions appreciated.

[murraymints]

you need builder or his mate !!!

[SlackAlice]

First off
Does the lockshield valve look similar to these?

http://www.wickes.co....421550/?source=123_75

If you remove the plastic cover, normally a push fit or occasionally a small screw. Quite a tight fit sometimes.
Underneath is the valve body. You should be able to see a valve gland nut. Carefully tighten this and it will probably stop the dribble (not too much or you will be unable to close/open the valve). Be aware that they are usually made of soft metal, do not use excessive force. If the dribble persists then renewal of the valve should be considered.

Let us know if you've still got problems and one the more plumber orientated ABer's will join the thread at some time.

[davidk65]

Hi. Thanks for the reply. Yes the lockshield valve looks like those in the link you gave.
When the plastic cover is removed from the valve the valve spindle and gland nut do not protrude above the valve body. Looking down on top of the valve (with the cover removed) one can only see deep inside the valve body a screw drives slot, it is when I turn this, clockwise to shut the valve, that water begins to dribble upwards out of the valve passing the spindle. At first it was difficult to turn with a screwdriver but it then moves freely clock and anti clock. I assume the spindle is fitted with some sort of seal like an O ring and this has failed. In connection with replacing this valve it is how much draining down I would need to do?

[The Builder]

It does sound as though the gland is leaking, David.
Turn it to "off". Do the same to the Thermostatic valve at the other end, then take off the rad. Have plenty of cloth down to soak up the water, and turn the rad upside down immediately (to stop it from draining).

You'll need to screw a blank into the nut that was screwed onto the rad. Then you can turn the lockshield back on again, as I guess it doesn't dribble when it's in the "on" position.

That's only if you don't want to replace the valve. If you do, then you will have to drain down. Most combis have to be re-filled manually afterwards. I can tell you how to do that, but you can leave the hot water on. Remember to turn the heating off at the boiler though.

Alternatively, buy a small freezer kit (or rent one). Very simple to use. Just use the kit to form an ice plug in the pipe run to the lockshield valve. You'll have a good 20 mins to change the duff valve.

[davidk65]

Thank you to "The Builder". I like the idea of freezing the pipe rather than draining down. I see Wicks have kits for about £12 which come with a jacket. Can the jacket be cut to size, as I only have about 3 inches of pipe showing between the valve and where it comes out of the wall, in those circumstances would it work??

[ChuckFickens]

Probably not, you're meant to leave about 20cm between the jacket and the fitments you want to remove so you don't freeze the water inside the part you're working on.

[The Builder]

Yes, that is a problem. I usually go under the floorboards for this, but in your case, you would need to get into the wall to find the run.

Unless you carry on with the faulty valve (assuming it doesn't leak when it's open), then I guess you'll have to drain. Look for a drain-off point on one of the rads............. preferably near an outside door. Then you simply push a garden hose over the spigot, and drain.

[davidk65]

Thanks again to The Builder. I turned off the C/H feed and return at the Combi boiler. I then removed the thermo heads from a number of radiators and shut them off as well. I drained the radiator and this seemed to create a vacuum which allowed me to dismantle the lockshield valve in situ. The "O" ring had failed and I replaced it and that part of the job was OK, but that was not the end of the difficulties. Because I needed to replace the rad with a new one I had bought a new lockshield valve. I fitted the new valve tail into the radiator but when I came to connect the old valve body to the new tail they were different threads and would not fit. To solve this problem I decided to remove the old valve, leaving the gland nut and olive on the pipe, and fit the new valve body. I then discovered the the valve body was a different thread to the gland nut and it would not fit. I eventually got the olive and nut of the pipe and fitted the new lockshield valve and apart from a slight leak all appears well.
Because I have had to drain down a couple of times I have lost the water and inhibitor how and where can I replace the lost chemical from the system?
Thanks again.

[The Builder]

Too much to expect any standardisation isn't it, David? Many times I've had to re-use the old rad tails so that I could re-connect.
That's why plumbers keep a mountain of old bit and pieces in the back of the van :o(

Well done to you though.
A simple way to replenish the inhibitor is to unscrew the blank at the top of the rad (opposite the bleed valve end). Use a funnel and a short length of plastic tube.