Unvented cylinder - turn off hot water

I am living in a house with an unvened cyclinder in the hot water system. It is of the Megaflo type.
I would like to turn off the hot water to disconnect an old shower but cannot find a hot water stop cock only the cold water one in the kitchen.
Can I just turn off the cold water and allow the cylinder to drain below the shower level or is that not possible with an unvented cylinder?
I know these things have "bubbles" in them to allow for expansion but I do not know whether I can safely partially drain the cylinder without having to call in a plumber.
I have tried searching the web and have looked at current messages in this group but have not found a definitive answer yet.
Can anyone help, please?
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There should be no need to drain the cylinder at all. If you cut off the cold feed to the tank, then no water will come out of the top, as it needs to be pushed out by the mains pressure.
Try turning off the kitchen stop cock. The hot taps throughout the house should immediately stop working. Sure there will be a few dribbles, but as long as you use a compression joint to connect to the pipework, there shouldn't be a problem. Compression stop ends are easily obtained, but try to install very close to the original T, so you don't have a load of stagnant water sitting around. Better still is to remove the T, but this is more work.
Christian.
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