Fitting a 28mm gate valve?

Hello, has anyone fitted a new gate valve in the pipe from the header tank to the hot water cylinder? I had a go yesterday, but it appears that the pipes are so stiff that they cannot be moved enough to slide out the old valve, so I will have to undo the union to the header, remove the pipe from the header tank, then slide the pipe up the inch or so to remove the old valve.
Even if the header tank is empty, there are still overflows and inlet pipes attached which are all fairly solid looking, so it looks like there is not enough play to get the pipe up a little bit.
Any tips to do it, or should I just drain off, then remove the upper part of the pipe to allow fitting of the new valve?
Ta Alan.
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On Sat, 16 Jan 2010 15:25:01 +0000, alan@darkroom.+.com (A.Lee) wrote:

Dunno if you can get them but could you take a piece of the pipe out then use a 28mm slip feed connection or 2 and a piece of new pipe if you have a bit lying around which should enable you to get the new valve in ?
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On Sat, 16 Jan 2010 15:25:01 +0000 someone who may be alan@darkroom.+.com (A.Lee) wrote this:-

I'm sure somebody has:-)
Many have probably been lucky enough to be able to replace the valve relatively easily. Installations are different and there may be many ways to get the ends of the pipes far enough apart. Dismantling compression fittings may work, as might springing the pipes. Different approaches are often necessary when the cylinder and tank are 8m apart compared to them being 1m apart.
If you have access to the fitting where the pipe enters the cylinder then this can be the best one to remove to get space. Obviously this means draining the cylinder first, unless you want to be covered in hot water.
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David Hansen, Edinburgh
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On Sat, 16 Jan 2010 15:25:01 +0000, A.Lee wrote:

I'd steer clear of the bottom feed connection into the cylinder - potential for nasty leaks there. I'd be inclined to cut the pipe further up from the valve you're replacing so you can take out a short section, then get your new valve in and re-join the upper cut with a compression coupling, cutting the intermediate pipe to just the right length that you can assemble valve, coupling and pipe without having to spring everything apart, and carefully doing up the compression joints so that you have a reasonable length of pipe going into each joint, IYSWIM.
And I'd use a lever ball valve rather than another gate valve, but then I've seen enough duff gate valves to loathe them with a fervour I cannot begin to convey :-)
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John Stumbles -- http://yaph.co.uk

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On Sat, 16 Jan 2010 15:25:01 +0000, A.Lee wrote:

=============================================== You can make your own slip couplings if you need to and they're certainly worth doing. You'll need a suitable reamer to cut out the central stop in the coupler but you might manage with a good round file. The important thing is to avoid damage to the olive seatings.
You'll need to make sure that you've got enough space to accommodate them as you'll probably need to use two.
Cic.
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A.Lee wrote:

if you really can't get any sufficientmovement,cut the pipe and use a slip join http://www.tbsmerchants.co.uk/cgi - bin/build/detail/PS02120R_Yorkshire_YP1S_Slip_Coupling_28mm_.html these don't have a centre stop, so will slide over the pipeallowing you to re-join the bit you cut.
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On Sat, 16 Jan 2010 23:06:11 GMT

Yikes! Look at the price of that! Over £15 if you need two, as you might. This is a better price for a YPS1:
http://www.jtmplumbing.co.uk/yorkshire-copper-fittings-118.html
R.
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TheOldFellow wrote:

YPS1 is a Straight fitting, and not what i was talking about at all. YP1S is a Slip fitting, 7.90 is in fact the rrp for them, but you can find them cheaper.
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Can you not just swap the guts of the old gate valve with the new gate valve? I have done that before when they have failed.
Adam
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First thing I tried. Totally different thread size, and the old shaft was stuck solid, so i refitted it after taking out the broken gate, and was going to leave it until another day when I could drain it down properly. The gate valve had broken in the closed position when I went to turn off the hot water. Rather annoying when all I had to do was change a tap tail. I had plugged the tank outlet with a latex glove packed with tissue, so didnt really want to mess around with it too much with such a flimsy bung holding 50 gallons+ of water! Ta Alan.
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On Sun, 17 Jan 2010 11:48:19 +0000 someone who may be alan@darkroom.+.com (A.Lee) wrote this:-

Work them once or twice a year. Fully close, fully open and leave a quarter turn shut. Then they work when needed.
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