Replacing An Immersion Heater Supply Gate Valve

[j0nb0y]

I was fitting some new bath taps this evening. I closed the gate valve which feeds the immersion heater from the tank in the loft to turn off the hot water, without having to drain the tank. Fitted the taps, turned on the mains cold and then went to turn back on the gate valve to turn on the hot water supply. The flipping thing broke,( in the closed position ) so unable to turn on the hot water. My question is, how do I drain the tank in the loft to be able to replace the gate valve? Obviously the tank in the loft is still full of cold water, so as soon as I undo the top half of the gate valve, there is going to be water.
any help, advice or suggestions, much appreciated.

[johnk]

which part of the valve has broke, has the stem snapped?

[j0nb0y]

No, the handle just keeps turning, so presuming the spindle has snapped. So now it is in the closed position.

[johnk]

can you get to the bottom of the tank and force a bung into the outlet?
Then you'll only have to contend with the water in the pipes.

[netherfield]

Otherwise buy a pipe freezing kit.

[donny48]

Is there enough of the stem left to be able to grip with pliers, molegrips ?

[Etch]

I would hope that the loft tank has a lid. If so then bail it out using saucepans/buckets. Alternatively, use a length of tubing/hosepipe to siphon the water out of it.

[Atheist]

following on from Etch... Don't forget to turn off the supply to the tank, by tying up the ballcock arm, or shutting a valve if there is one.