Water shut off, tank drained and now no hot water..


We installed some new taps at a friends flat. Slight problem in that we couldnt find the stopcock (subssequently discover its in next doors flat...go figure!)
Anyway, we managed to isolate the kitchen sink ok and installed the new taps.
Now, problem is, that once all the valves we shut off were re-opened, no hot water came back in to fill the storage tank (or at least if it is, its doing it at a dribble..)
The storagfe tank had to be drained down to perform the works, but cant work out why no water is coming in to re-fill the system.
The system is of a sealed typ (no open header tank). There is a grey pressure vessel in the loft crawlspace that has a red valve on top that hisses when turned, and a pressure guage on it. The pressure guage reads 0 atm, but will rise a little (to a 1/4 bar) if left overnight.. I assume this is the pressure releife system, as its hooked into the drain pipe that pokes out of the outside wall..
If we leavce the system for several hours, the tank seems to fill a bit, but turning a tap on quickly drains this (in like 15 seconds..) We had the gas turned off as well, but that is now back on and the pilot on the boiler is lit.
Im stumped.
Any sugestions people?
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Had a similar thing here turned out to be airlock in the system. Had to back fill hot system with mains pressure. Simple hose connected from mains tap in kitchen to hot tap.
Hope this helps
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Were any 'gate valves' involved? If so often when they are closed after long periods of non use, the brass innards shread leaving the valve in the almost closed position.
This happens so often that I am amazed they are still allowed to make and install the 'eeeeefffffing''' things.
Peter

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Peter wrote:

What would you recommend instead? I've been looking at ball valves and isolation valves (the ones you use a flathead screwdriver with). I'm not sure what the mechanism inside an isolation valve looks like though.
John
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I use isolation valves.
P
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