Can I repack the stem of a pressurized globe valve?

The main water shutoff valve inside my house is a globe valve, and it leaks a little around the stem. I have tightened the packing nut a few times, but it always starts leaking again pretty soon. The valve shuts off the flow /through/ the valve pretty well though.
I don't want to have the city come out and shut off the water from the outside. I don't even know if their valve still works, as I don't know that they have operated it in about 40 years.
So I want to repack the stem with the valve closed and the line under pressure. Will that work okay?
It is a Nibco 3/4" NPT right-angle bronze globe valve from the late 1960's. Where can I find replacement packing? Will it be a rubber washer or what?
Thanks.
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On 1/31/2011 3:40 PM, Matt wrote:

Its their problem if it doesn't. Now would be the time to find out.

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Others have cautioned about removing the valve bonnet while system is under presssure. I would add the following information. The rope used for packing is called oakum and is hemp or jute rope infused with oil or tar. Its other use is to caulk open seems of wooden ships.
Joe G
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On Mon, 31 Jan 2011 16:55:57 -0800 (PST), GROVER

Valve packing is infused with graphite, or something close. I don't know the material that makes up the strands. High pressure packing like I used in the Navy is wire reinforced. We cut rings, didn't wind it. Offset the ring gaps about 1/3rd the stem circumference. Packing width had to be matched to the stem-to bonnet wall exactly. It was standardized though 1/4", 5/16:, 3/8th though, so it didn't take much thinking. I've had more problems packing home hose faucet stems with the odd size stuff from the hardware stores than sealing 1300 psi steam valves in the Navy. Maybe because I wind it. Seems to stop it from leaking you end up with a stiff valve. You should probably measure what width packing the valve needs, and cut rings. Valves are cheap. Next time my hose faucet stem starts leaking I'll put in a new valve. Oakum packing uses some kind of tar, and is also used on steel ships with riveted hulls. When I was in the Merchant Marine and watertending on the Rocket, a Cleveland Oil tanker, the Skipper had us dead in the water in the middle of one of Great Lakes, can't remember which. He put on scuba gear and went over the side with oakum and whatever driving tool you use for that. I heard there was a leak in one of the plates. Maybe he was showboating, but it's good to have a Skipper that can do "things" like that. I wouldn't try to pack a valve with pressure on it, but you might get away with it.
--Vic
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On 01/31/2011 08:57 PM, Vic Smith wrote:

I will look for packing rope of a diameter the same as the gap between stem and bonnet wall.
If I cut rings, should their lengths all equal the circumference of the bonnet wall? Or maybe the circumference of the middle of the gap? Or something else?
I guess I would cram the rings down the bonnet one at a time using the edge of a PVC coupling of an appropriate diameter. Is that approximately how you would do it?
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On Mon, 31 Jan 2011 22:49:58 -0600, Matt

You ''ll see the length to cut when you wrap it around the stem. Problem is the high pressure packing I used in the Navy was square in cross-section, and I don't think you'll find that for your valve. Try to get packing that's a tight fit between stem and bonnet wall. when you wrap it around the stem. Mark it with a knife/razor so the ends butt with no gap when you put in the ring, then cut it and put it in. Even with round coss-section packing, it should work. I had to cut the wider high pressure stuff at an angle to get a clean butt, but you shouldn't have to worry about that with the soft packing you're using.

That's good thinking. Any tube that fits well will work. Push it down, then tap it lightly with a hammer. You'll be tapping on the gland at the other end of what tube you use. The valves I worked with all had split packing glands, and I would put in a ring and push it down with the gland. Next ring, or third ring would require putting an open end wrench on top of the gland and rapping them down by whacking the wrench with a hammer. Don't know what kind of gland is on your valve. You'll find it under the gland nut. Probably a solid gland, like a bushing. Seat each ring well using the gland. Don't put so much packing in that the gland nut can only grab a few threads. You don't want to strip it.
--Vic
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On Mon, 31 Jan 2011 23:20:27 -0600, Vic Smith

BTW, I still don't recommend repacking with pressure on the line. Might be okay, might not. I've noticed with these small valves that the stem to body threads are a pretty sloppy fit. I think the packing around the stem gives that fit stability. It's possible that pulling the packing will allow the movement of the stem and let the disk move on the seat. Just a "feeling." You're going to need scribes to pull the old packing with the bonnet on. We called them scribes anyway. Something like this (Amazon.com product link shortened) But I got a better set somewhere else for about 5 bucks. Can't remember where.
--Vic
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On 01/31/2011 11:32 PM, Vic Smith wrote:

I hadn't thought of that. Maybe I'll loosen the packing nut and try to wobble the stem to get an idea of how tight the fit is. If I get sprayed or get a wad of packing up my nose, I'll know the stem is way too loose to do the operation. :-) At worst I will have to put it back together, close the valve, and go without water while waiting for the city to come out and shut their valve.

Thanks for the tips, Vic.
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On 01/31/2011 11:20 PM, Vic Smith wrote:

Maybe you guys cut the packing into rings because you can't use the gland to press a coil one loop at a time.
But I guess I could press a coil a little at a time if I used a tube that had a section cut out of its circumference. What would you think of that?

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On Tue, 01 Feb 2011 16:16:18 -0600, Matt

The gland is too tight a fit to allow any packing to stick out, so that rules out spirally it. The cut rings with staggered gaps worked fine. I'm not an engineer, just followed the established practice.

Neat idea. Like a weed whacker string. As I recall packing the few home valves I've done, I would spiral what I could around the stem, pushing as much into the body as I could, then would snip it and use the gland to push it down, then repeat the process, probably just once. Always fixed the leak, but I always thought the valve turned harder than I like. But the last one I did, maybe 5 years ago, the front garden faucet, turns easily now, so maybe the stem just has to wear into the packing.
Hey, I think you know more about packing valves than me now. Good luck, and be careful You don't want a flood.
I dealt with a similar situation when I re-piped the galvanized in my last house, a 2-flat. Stuff was about 50 years old. Water flow to the faucets was getting real poor. Shut off the city water valve myself, a gate valve under a small manhole cover on my front lawn. It was very stiff and I figure scaled up. I worked it opened and closed maybe 10 times trying to stop the flow to the basement sink.
The main valve in the house that you're working on was cranked down tight too, but leaking through. Same flow whether it was opened or closed. All other valves in the house were open. Best I could do was get it down to a weak stream in the sink.
I had a new house shutoff valve with nipple ready to attach to the lead service pipe when I took it apart. Taped and with the valve open. Had a buddy sitting on the floor holding a washtub to catch the water. When I broke the union after the valve he caught the same small stream that had been going into the sink, and I moved that pipe out of the way. Then I cranked the old valve and nipple off the lead pipe. It was like a fire hose had been opened. He was facing it and put the washtub up like a shield to protect his face. I got the new valve/nipple on pretty quick and shut the valve. If the valve wasn't open it wouldn't have gone on. We got pretty wet and probably lost a few gallons of water on the floor. Having the new valve ready to crank on was important.
My point here is if the pipes are scaled up it hard to know how bad the city valve is leaking through. I was really surprised with the volume and pressure I got from the city feed. Closing that city valve was almost useless. Didn't have much travel, so I probable never got it but half closed. But I didn't want to break it and have to call the city out.
The pipe I replaced was scaled bad. The 3/4" maybe down to 1/2" Hot water was much worse. At the joints it was barely open
--Vic
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