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metadog's avatar

How do I fix/identify a leaky brass gate valve?

Asked by metadog (319 points ) March 27th, 2011

Hi! I have three brass gate valves surrounding a filter for my well. They are starting to show some signs of leaking. I realize that I might need to replace them… or, there seems to be a couple of places where they could be adjusted. Is this something I should do? Or, if I need to replace them, can you help me put a name to this type of valve so I can have an easier time tracking them down?

Here is a photo:

http://www.flickr.com/photos/creativehaze/5564992908/

Thanks!

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8 Answers

WasCy's avatar

You didn’t say where the leak is occurring, but I’m guessing it’s in the stem under the valve handle. That’s the most common place for leaking to be a problem, unless the valve itself is failing at its job of closing off the flow in the pipe. (In that case, either the valve needs replacing or the system needs cleaning – and maybe straining / filtering of the flowing media – to prevent debris from preventing a 100% closure of the valve.)

So if the leakage is occurring at the valve stem, then what you’ll want to try first is tightening the gland nut by ¼ turn at a time (don’t go hog-wild here) until the leakage stops. The gland nut is the brass nut around the stem in your photo. (Remember: ‘righty-tighty’ – turn the nut clockwise as you look down on it through the handle.)

If turning the nut doesn’t solve the problem, then you may need to replace the packing. This is a job that should NOT be done while the piping system is pressurized. You should turn off the flow upstream from this valve and drain the system before you loosen the gland nut to remove the old and replace new packing material.

Any capable hardware store clerk can advise you on the packing you need if you show them your photo – and advise them if your system is for anything more than water.

Ron_C's avatar

I agree with @WasCy about tightening the gland but didn’t see any sign of leakage on the valve. By the way are you sure that it’s a gate and not a needle valve?

If the valve is leaking through, the most likely cause is dirt or deterioration inside the valve. Dirt and small rocks can be cleaned out, deterioration requires replacement of the valve. Did the valves freeze? If so, my experience is that the valve body or brazed pieces break and the valve needs replaced. Further, if I planned to replace them, I would use a ball valve, they are cheaper and less likely to freeze up.

WasCy's avatar

@Ron_C I agree that it doesn’t really appear to be a gate valve, but the type of valve is irrelevant if the leakage is at the stem; it’s still a packing issue.

On the valve in the foreground in the photo, you can see the greenish discoloration at the top of the gland nut, which is evidence of minor leakage. But if you look at the valve in the bottom of the photo… that one has serious issues. And we don’t even know what that duct tape is covering.

Finally, your suggestion to use a ball valve is good for simple “all open” or “all closed” valve applications, like you’d often use for a washing machine inlet or hose bibb or other place where throttling can be controlled elsewhere (or throttling isn’t necessary). Throttling a ball valve in the “slightly open” position can damage the seats. (Which I didn’t know myself until I started to do some research on the packing issue earlier; I’ve never replaced a valve stem packing myself.)

Ron_C's avatar

@WasCy I am a bit colored blind in the blue/green/brown range and didn’t see leakage until I looked closer. Considering that information, it looks like the packing gland isn’t held down tight enough by the gland nut. Considering this small leak, tightening the nut will probably do the trick. I also use a little trick. If the water supply can be shut off, I dry off the valve and spray the stem and packing with silicon. This enables you to tighten the packing gland further and still be able to adjust the valve.

As for ball valve deterioration, the same applies to gate valves for high velocity or abrasive liquids. I suspect that there wouldn’t be much difference in longevity for water valves in household systems. The balls are stainless steel and the seats are Teflon (at least the ones we use). Once either valve is opened more than 50%, fine flow adjustment is lost.

metadog's avatar

Thanks, guys! Tightening the gland nut seemed to do the trick. The photo I showed you was not really the offender. That one was in the back on the top (above the duct tape – harder to take a picture of). The one in the back on the bottom was getting dripped on until I discovered the issue (thus the mess). I used the duct tape to redirect the water until I could find the solution. One thing this adventure did teach me is that I have more than one valve with an issue. Here is a photo of the actual configuration:

http://www.flickr.com/photos/creativehaze/5566239728/

The one in the original photo is the valve on the right.

The water leaking out was blue. I am guessing this has something to do with the interaction between the minerals in the water and the metal valves. Either way, I am now thinking that I will need new valves. They are only 10 years old, but I have already had our water eat out the bottoms of my hot water heaters. Lots of minerals and lots of silt coming from my well.

Would ball valves do anything to increase water pressure? Cut down on the drag caused by the gate valves?

THANKS!!!

Ron_C's avatar

The CV or flow coefficient of a valve is a measure of fiction or resistance to flow. The only effect a valve would have is to decrease the flow coefficient below what it would be if it was just a piece of pipe.

If you build pressure (without changing head pressure) you decrease flow. If you want increased flow, you open the valve. The only way to actually increase flow and pressure is to use a higher capacity pump, or for a dam, increase the height of the dam.

WasCy's avatar

Actually, there’s something in the most recent photo that makes me the most concerned, and that is the proximity of the electrical switch to the possibility of flowing water or water on the ground (when the filter is removed, for example). I’d be very leery of operating that switch in that location unless it’s protected by a GFCI or something similar. (I just don’t like electricity near water, period.)

But to get back to your question: blue water? Have you had the water tested at the well head for pH and whatever minerals are included? It does seem somewhat corrosive (acidic, maybe? pH is easy to test), to have eaten up the inlet valve so soon; you may need stainless for the shutoff and filter inlet. It seems that the filter itself neutralizes the water to protect the lower valve at the filter outlet.

metadog's avatar

That is the well pump switch. It is on a GFCI. Believe me, its proximity to a water source is the least of the issues I have with how this home was constructed. Don’t get me started on when my sump pump failed and I had 3 inches of water in my basement last fall… totally preventable with a little common sense.

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