Help replacing gate valve - more help needed please!

Hi

My water is currently off as I'm doing up my bathroom.

While I'm at it, I'm thinking about replacing the broken gate valve in my airing cupboard (I have bought the correct 22mm replacement valve already).

However, before I proceed, I'm a bit nervous about it as when I started to open one end of the broken valve, water came out. Now I know there is going to be 'some' water that is already in the pipe, but can someone confirm just exactly where I need to turn off the water to prevent a flood while I'm doing this?

I have provided links to a couple of photos, but for clarification, the pipe in question comes down from my loft and down into the BOTTOM of my hot cylinder. Before it enters the cylinder, there is a drain cock.

I have turned off the tap in the loft (on the pipe leading out of the water tank), so do I just need to empty the pipe using the drain cock then remove the valve, or will water come out of the cylinder and up out of the pipe since I have removed the water pressure coming down from the tank? Is it even necessary to drain this piece of pipe (will there only be a bucketful or so?

Pictures are HERE

Hope that's clear!

Thanks[/url]

If it is the same pipe in both photos this will be the cold gravity feed from the cold water tank into the cylinder. To change the valve you need to drain the cylinder to a point below the height of the valve. You can do this initially by stopping the feed to the cold tank and running the hot taps, then you will need to drain water using the cylinder drain cock.
I can't tell from the photos at what height the valve is relative to the cylinder but as I say, if it is lower than the top of the cylinder you will need to drain the system to below the height of the valve.

Hi

Yes, it is the same pipe on both photos and the gate valve is about 6" higher than the top of the cylinder.

So if I've understood you correctly, I need to:

1. Turn off the valve from the rising main into the cold tank (done)

2. Turn off the tap (in the loft) on the pipe coming out of the cold tank down to the cylinder (done)

As the valve being replaced is higher than the top of the cylinder, I dont need to drain the drain cock going into the bottom of the cylinder (as shown in the 2nd photo)?

Many thanks for your help

You should still run the hot taps as this should empty the pipe down to level with the top of the cylinder but that is all you need do.

How old is your pipe work? If very old and imperial size pipe (3/4") you will need to buy 3/4" olives and remove the 22mm that come with the gate valve

True - though I'd usually be too lazy and wrap several turns of ptfe round the old olives in situ and hope for the best...

It's ok, the original gate valve was 22mm.

I'm pleased to announce that in 2 days I have gone from complete plumbing novice to having:

- Drained down open vented system
- Replaced broken gate valve (with only one mild moment of panic until I realised I should bung the cold tank)
- Moved pipework for (and fitted) new WC
- Plumbed in new basin (complete with changes to pipework)
- Fited new pipework (including 10-15mm reducers) for new towel rail
- Re-Filled Central Heating and added inhibitor

And hey-presto! It all works with no leaks (and hopefully it'll stay that way!)

Thanks to the guys-in-the-know at diynot.com - couldn't have done it without you.

Now, what's going to be my next project?

very good post to make sure that the water coming out of the cold water tank is shut properly in the loft I want to run the cold tap in the bath . When I do this procedure and no more water is coming out shall I close the tap in the bath before I reopened the cold tank outlet feed or leave the tap in bath open until the water comes back out?