What do you think of gate valves?

25 Jan 2004
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United Kingdom
After a post regarding a gate valve previously fitted where a stopcock should be used, I got to thinking about gate valves.

Out of 5 gate valves I have installed and used, I have only ever had one do its job 100%. And I found one seized that required a lot of WD40, a night to soak and then a big (but careful) spanner. What are the opinions of plumbers on gate valves?

Would lever ball-valves be a better solution than gate valves in terms of reliability and effectiveness?

Is there a different valve that would be better in place of a gate valve?

I am sure it can't be inherent in the idea of a gate valve, in the movies they are always using big versions of them to close off steam pipes in submarines and the like. Is it just that they aren't suited to being made cheaply I wonder?
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Full flow ball valves are replacing gate valves. GV's were never spec'd to hold much pressure 100%. You still need a screw down valve in the trad stop cock position though. FFBV's suffer from wear on the seal to the ball, and stick open if there's a lot of scaling.
I have used a few gate valves around my home in the past and I have found them unreliable i.e. not closing fully. So I have fitted FBBVs' instead. They don't seem to weep around the ball but the spindles do weep sometimes after they have been operated although they stop after a couple of days or so. I think some ball valves (with the yellow handles) are only suitable for use at 60 deg C max. Perhaps this is something to do with it.
I never fit gate valves unless its a quick 1-1 replacement where it would be impossible to remove.

Several gate valves have stuck shut. In this case the spindle appears to screw out of the body! They also weep over time.
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So, the consensus is that gate valves are c**p then. Not just me!

You see they are so familiar, which is why I used them in the past. There were already gate valves on my plumbing so I assumed I should use them too.

I will be using FBBV's in future. Something more satisfying about a quarter turn on a lever than twiddling a little red wheel like it's some kind of crazy spoked nipple. And no matter how hard you twist it, you don't get the desired effect.
So why not just use a reliable stopcock? Is this a cost thing or does it have to do with the ability to flow in both directions?
Horses for courses!

A gate valve has NO sealing washer (so cannot be 100% tight and not intended to be) but when fully open hardly impedes flow. A stopvalve has a washer (which will quickly deteriorate with water hotter than (say) 60 degrees, and DOES impede flow when open.

For isolating parts of a central heating system and / or adjusting flow rates, use a gate valve. To stop high pressure cold water dead, use a stopvalve. If the spindle leaks, the gland seal can usually be tightened.

Lever-operated FFBVs are also good for isolation, not so good for regulation, but once they start to leak, they're useless (for example, the isolating valves on a well-known Combi boiler).

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