Loft Cold Water tank and Gate Valves.

Thanks for reply DD.

Yes I did turn off the mains and ran the cold taps in the house until they stopped running.

The problem is that even after doing this there is still a cold feed to the shower. 
Looking at the pipework > There is one pipe which comes from loft CW tank and it comes down into the airing cupboard > thru the Gate Valve > then direct thru the wall into back of the Mira Shower. It doesn't feed anywhere else.
So I think (obviously no expert) that this pipe is solely for the shower and doesn't go anywhere else > and if I can't close the gate valve then it will keep flowing to the shower until the tank is empty.

No problem, the more input the better.
I maybe didn't explain very well.  Here are the main steps I did. Actually listing it made me realize where I went wrong (maybe).

1. Turned off rising main.
2. From Loft CW tank there is a pipe which runs down into bottom of cylinder > so this is cold water feed to the cylinder (in airing cupboard) and is in effect the feed to hot taps (as I understand it) > Closed this as well. (belt and braces)
3. From Cylinder in airing cupboard there is main pipe which comes out of top > this is the feed to hot water taps (as i understand it).  This pipe splits into two > one for taps and also one which goes thru gate valve and then into back of shower > closed this gate Valve ok as it turned fine.
4. From Loft CW tank there is a pipe which comes down into airing cupboard > thru a gate valve > into back of shower > This is the gate valve I couldn't close.
5. Ran taps until they stopped. 

At this point, If I try to mess with the shower, there is still a cold water feed coming into the shower.

So to my mind the cold water tank in the loft is not empty and it has to be empty in order to stop the cold feed into the shower as i can't close the pipe in Step 4.
The cold water taps are mains fed i think like you suggested as they stopped running after a few minutes.

Anyway, thinking about it, I guess I could empty the cold water water in loft by not doing Step 2. In which case if I kept running the hot taps, the water would continue to flow from CW tank in loft into the Cylinder. But it wouldn't be replaced from the mains as I have turned off the rising main. Then eventually the CW tank in loft would run out of water ?  

P.S I didn't go into the loft to visually check the level. I guess I should have done really, but man it was hot up there and then we had people come round and i was already sweating buckets..lol
P.P.S > yes I could keep running the shower with mains turned off > but at the moment there is no shower tray so no where for water to go.  ( I should have mentioned that ..apologies)


Thanks for replies so far.

Get a rubber bung & stick it in the hole in the cw storage where the cold flows from to the shower, turn the cold shower / tap on & make sure it’s not running, they’re maybe a little bit giving way, that’s ok, undo the gate valve nut &’slowly pull the pipe out, there may be some water, if you’re confident swap the gate valve for a lever valve, do the same for the hot while you’re at it.

Get some plumber boy(my nick name for them)bungs in the tanks and stop the flow. the gate valve has snapped inside, that is why it's spinning, definitely replace with lever valves as dafty says👍👍👍👍👍

Thanks very much for all help and replies.
I'll have a look in the CW tank in loft to see how all the pipes flow.

Using a bung to stop the flow sounds like the way to go. 

And I'll have a look at replacing the gate valves with full bore lever. For these, the cold water one should be ok as I will have stopped the feed from CW tank in loft.
With regards to the hot one > I currently don't have an isolation valve from the main pipe coming from the top of Cylinder. Would I need to reduce the level of water in Cylinder before undoing the hot water gate valve ?
I guess I could close that gate valve and install the lever valve further up the pipe. Then I would have two valves on the hot pipe. Maybe confusing, but not that bothered by it since it is our own house.

Couple of pictures attached.


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Only thing is do those bungs work up to 28mm tank connectors? As a DIYer I#ve no idea if such connectors are common but in my house, they are used for both hot and cold feeds out of the tank. The shower feeds are obviously 22mm.

And one question on airlocks. Can they be avoided by keeping most/all taps open until they start running when filling up? Maybe or maybe I've just been lucky here with the way the pipes are layed out but don't think I've had an airlock on the HW. Had plenty of the CH though !