Replacing Radiator Valve

4 Jan 2007
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United Kingdom
I need to replace a valve on my upstairs bathroom radiator as the 'head' is cracked and the rad cannot be turned on brrrrr.

There is a combi boiler system in the house. There is not a 'drain off' on the pipework for the heating. I assume that in order to drain down the system to replace the valve I need to:

a. Turn off the water coming into the combi from the mains. The combi has a filling loop.
b. 'Open' the pipework (by cutting) at a low point (ground floor) to allow the water to drain off - whilst about it may as well fit a new drain off?
c. Bleed the radiators to allow complete drain off.
d. Replace valve!
e. When turning the water back on the heating pipework is filled again from the filling loop?
f. Turn water and boiler back on.
g. Re-bleed radiators (does it matter in what order these are done?).

I think this will work, though confirmation would be great. My thought is that this is a lot of work to replace one valve. So firstly, is there an easier way of doing this? And, have I got it right if I go ahead with the method above?
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If it is just the plastic head that is cracked you can probably just change that. It will probably just pull off to reveal a flat end to the spindle. Some have a fixing screw and a square end.

If you take an undamaged cap off another valve with you to the plumbers merchant you can see if it will fit a new tap. You will probably have to buy a complete tap but they are only a couple of pounds.

If you have to fit a complete valve buy a thermostatic one which is dearer but more energy efficient.

You will not have to drain the system to fit a new valve. As it is sealed, water can only come out if air gets in. Shut off the rad at the both ends. When you slacken the joint water will gurgle out odf the rad but you can catch it with a basin and old towel. To make it come out faster loosen the bleed valve at the top. When you remove the old valve a little water will trickle out, then it will stop. Do not open the valve at the other end. Observe the water that comes out to see if it black or contains sediment or sludge.
if its the spindle that broke, then try turning all rad valves off to each rad to save as much draining down as possible, also not recomended, but you could then use the prv in the combi to drain the upstairs thats if the boilers downstairs .

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