Can't drain hot tank

[Vicario]

I want to replace my immersion heater and need to drain water from the top of the hot cylinder before I unscrew it. I attached a hose to the drain cock at the bottom, turned the nut and.....nothing. The drain tap is obviously furred up inside (the cylinder is very old). The sparky who came to fit the new immersion heater was there when I tried this (I'd agreed to get the tank drained myself before he came) and he said that he'd seen plumbers disconnect the pipes at the top of the cylinder to drain some water off that way. He also said that he'd seen a new drain cock fitted beside the old one while the tank was still full - is this possible? Anyway, any advice appreciated. (The spark didn't charge me, by the way, but will come back when I've managed to drain some water off by any means available.

 

[seco services]

what ever you do make sure you isolate the feed to the cylinder.
run a hot tap till the tap stops running
slacken the pipe on the top of the cylinder and hold a towel road the top and remove the pipe from the top of the cylinder.
place a hose in the top and drain a few inches off.

or place a towel on the floor under the draincock place the hose on the draincock and remove the draincock you'll probably find the washer is jammed up the hole.
when it starts flowing refit the draincock.

there is a number of ways you can do it.

if you had got a plumber in the first place he would have done both jobs.

 

[doitall]

I don't like touching very old gate valves, instead I would tie the ballvalve up or turn the mains off and open all the taps.

 

[advancedplumber]

fair enough doitall, but sometimes u can get air locks draining down and surely thats one headache this chap doesn't need to be typing in next i would plug the tank with plugging kits. draining down is also time comsuming.

 

[kevplumb]

seco has the plan

ok forget the valves tie the ball valve or turn the lot off

jeez it's only a 10 min job