Wamsutta
Well-known member
Which is better; Teflon or Graphite?
Valve Stem Packing String
- Thread starter Wamsutta
- Start date
Beerhippie
Well-known member
Yep.
TurnipTruck
Well-known member
Depends upon the temperature. I would use graphite above 200F or so, Teflon below.
Firebrick43
Well-known member
Teflon also does better with acids and bases, but definitely don't use teflon in high temps or its poisonous. I don't know about all teflons but most are good to 300 or so degrees. Definitely not furnaces or high pressure steam.
Main water shut off gate valve 1-1/2". Made out of solid bronze. Age is somewhere between 60 and 70 years. Wish I could just replace the whole valve, but the steel pipes connecting to it are corroded in place. I tried measuring the stem diameter a few minutes ago and my 12mm wrench fit on it the best. 11mm is too tight and 7/16 is too loose. 12mm just right. My next venture is seeing if the stem is replaceable. It's got wrench flats to loosen the stem assembly, but I don't dare unless I'm sure.
alfadan
Well-known member
I've used graphite on water valves. Works fine.
TurnipTruck
Well-known member
Fully shut (or fully open if machined to have a backstop) should slow the flow enough to allow you to repack, especially if it’s just rope and not rings.
TurnipTruck
Well-known member
You angle cut the beginning of the square section Teflon rope and wrap it around the stem a couple times to fill the stuffing box, assuming you dig all the old packing out, tamping it down with the stuffing box gland follower. This is also assuming it’s an OS&Y (Outside Stem & Yoke) with two bolts holding the follower down, and not a giant threaded bonnet. A little baby 1-1/2” valve could have either.
You may be successful just adding a ring or two of packing and tightening it down on top of the existing packing.
Some of the problems I have experienced over the last 40 years with valves in the oil field include rotten yoke bolts, fatigued stems snapping off or stripping threads (especially if they are brass or bronze or anything else not chromed) so the stem either doesn’t rise (stripped body) or turns without end (stripped gate), or the gate fingers break so it separates from the stem, or the stem breaks above the backstop so the stem blows out and you get wet, stripped handles or wheels, cracked bodies that separate when you put a wrench to it, or soft seats that have eroded or break loose when disturbed.
In other words, be prepared ahead of time for maximum excitement, up to and including total isolation and replacement.
Beerhippie
Well-known member
Sounds to me like you just found that little five minute fix that requires re-plumbing the entire house.
If the galvanized iron pipe is that corroded, you're not too far from some major failures.
Oh I know that. I've had a trench dug in the front yard for years. I need to replace both the water line and the sewer line.Sounds to me like you just found that little five minute fix that requires re-plumbing the entire house.
If the galvanized iron pipe is that corroded, you're not too far from some major failures.
I ran into something called a "Valve Bibb Washer" on the internet. Man that would sure be nice. Slide it over the valve stem and then bring the packing nut down on top of it. No more rope to spring out and unwind. I wish I would've measured the inside diameter of the packing nut when I had a chance.
What difference does the diameter of the stem make, if you are repacking it?
What I'm thinking is I should try to find the correct size seal instead of using the packing string all the time which doesn't stop the leak completely. Right now I have a slow drizzle which is better than spraying all over the place.What difference does the diameter of the stem make, if you are repacking it?
Did you try to tighten the packing nut?
W seriously, how many decades is that packing material been in there?
When I worked for a plumber occasionally, we’d have to repack them because they had not been turned maybe in 30 years
I tried what you’re considering, but all valves are not the same as new valves
If I tighten the packing nut too much, the leak turns into a squirt and goes straight up the valve stem. I'm using Home Depot packing string. I think the Ace Hardware packing string I used last time is probably better quality. Next time I'm going to try the graphite instead of the Teflon. I would love to replace the whole valve put the pipes connecting to it are heavily corroded and aren't going to let go of the valve without crumbling apart and creating a bigger problem.
Firebrick43
Well-known member
Are you pre soaking the string?
How much string are you adding?
It needs to go on fairly thick. I wrap enough strands for the packing nut to just barely clear it.
Tightened it about halfway and see if it’s snug enough and if it’s still leaks, tighten a little bit more
Beerhippie
Well-known member
I think you're going to have remove the old packing to have enough room for the new.