How to deal with failed gate valves

[usenet]

Two of the gate valves on the hot water circuits from our hot water cylinder have failed. They are permanently open and turning the red handle does nothing, which makes doing plumbing jobs (see my other question about bath taps) rather difficult.

I expect something inside has sheared but I'm wondering whether I can replace just the 'innards' as it were. The mechanism part obviously screws into the brass part with two compression fittings that goes on the pipe, if I buy a new gate valve (I could even try and get the same make I suppose) is it a sensible/possible job to swap just the mechanism by unscrewing the old one and putting a new one in?

[John Stumbles]

You could do but gate valves rarely (IME) turn off tight so I usually replace with lever ball valves. This invariably means cutting back the old pipework as the ball valves are longer than the gate valves, and occasionally the old pipework is 3/4" requiring appropriate olives on the new valve. Whether replacing with a gate or a ball valve, depending how much give there is in the pipework it can be a struggle to prise the pipework apart enough to demount the old valve and reconnect into the new one.

[Andy Hall]

It would be much better to replace the valves with lever ball valves, Chris.

They don't suffer from any of these problems and do turn completely off with a quarter turn.

[usenet]

This is one of the reasons I was hoping to just replace the innards of the gate valve, it'll be much less hassle than trying to remove the whole of the old valve from the pipework.

[Cicero]

================ Wickes sell an adjustable telescopic pipe to facilitate inserting valves etc. where the gap is too small / tight.

Cic.

[simon beer]

I'll have to try these next time I get a gate valve jam on me. I always think they rubbish anyhow and as you say never turn off 100%. But what I have found in the past is that it is quite often the red disk that starts to rotate on the brass part of the valve. So as a quick fix to get the water off I have removed the red disk and put maul grips on the brass part and turned it then. That normally gets the badger!

[Set Square]

As others have said, gate valves are never very good - and you would be better off with full-bore lever-operated ball valves.

When you say that the red wheel is turning but the valve isn't closing, is the shaft turning? If it's just that the square hole in the red wheel has become rounded so that it no longer engages with the square end of the shaft, remove the wheel and turn the shaft with an adjustable spanner or mole wrench.

[usenet]

Yes, the shaft is turning, quite easily actually.

[Set Square]

In that case, the innards are shot. They are held in by a big nut which surrounds the shaft. You *may* find that you could swap them for the innards from a replacement gate valve - but there's no guarantee that they'll fit. There's a much bigger chance that the compression nuts and olives will fit, enabling you to swap the whole body - but you need to be able to move one of the pipes axially to do this. If you've got to do this, you might as well fit a ball valve instead - even if it means shortening the pipe slightly and re-doing one of the compression joints.

[usenet]

Yes, thinking about how a gate valve works and seeing as these are stuck 'on' I think the chances of replacing the innards are just about nil.

So I'll have to take a look and see what the chances of moving the pipes a bit are. Fortunately since the stuck valves are hot water ones I can turn of the cold feed to the cylinder (which does still work) and then very little water will emerge when I remove the valves.