Removing radiators on unvented system

[A dangerous thing]

Can anyone help me with what to do to drain down an unvented system so that we can remove a radiator in an upstairs bedroom? We had the system fitted about 2 years ago, and I haven't got a clue how to drain it so we can remove this rad.

Matt

[John Rumm]

You don't need (or want) to drain the complete system - just the rad in question. In simple terms you need to turn off both valves[1] and then undo one of the connections to the rad a little to let the water out (catch in a cat litter tray or small bowl - beware the water may contain black iron oxide which is a strong dye that will stain carpets if spilt.

[1] Many rads will have a lockshield valve on one end which can be turned off by removing its cap and closing the tap with a pair of pliers etc. The other end may be a thermostatic valve - some of these have a genuine "off" position which makes it easy. Some are supplied with a decorating cap that can be substituted for the thermostatic head when you want to turn it off completely.

Once the rad is drained, undo both connectors and use some small plastic bags over the connection tails fixed in place with rubber bands. This should stop any sludge falling out when you move it.

Remember the nuts on the rad are fixed to the rad and screw onto the valve - not the other way round. Hence they undo in the opposite direction to that which many people expect!

For more details see the FAQ here:

[Lobster]

Do you want to remove it permanently or temporarily (as John assumed below)?

Ideally you should make a note of how many turns (and fractions thereof) the lockshield valve was open before you start fiddling with it; if the system was correctly installed it should have been "balanced" which would mean the lockshield valves would have been set differently on each radiator for optimum results - so ideally, it should be put back as it was. (Although in the real world, when did a plumber ever balance a system properly?!)

David