Leaking Stopcock tap

27 Oct 2020
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United Kingdom
Hi, I have a very slow leak coming from the shaft of the tap on my stopcock (1 below), where the shaft enters the body of the stopcock - see photo below. This only happens when the tap is open, when it's closed, the leak stops.

Can I (after turning off the mains water at the stopcock outside my property) unscrew the nut that the tap goes into (2), to see if I can clean the inside? Or should I unscrew nut (3)? This is a twenty year old stopcock that I fitted myself many years ago, when I was building a new kitchen. The water supply pipe that comes up from below is black and flexible, and it was a non standard width, imperial I think, not metric, because it was from 1980, when my house was built. Does anybody know what that standard width was back then? I remember having to shop around before I could find a stopcock that would fit it, because it wasn't metric. If I can find that out, I can just replace the whole stopcock, but I thought it might be quicker and easier to unscrew the part where the tap goes in and see if there is a build up of limescale inside.
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Make sure the mains outside (your boundary stopcock) is free from dirt and debris and can be turned off, there isn’t a need to turn it off at this stage (if at all). Carefully back off the gland nut (number 2 on photo) add some ptfe, in a thin string type arrangement approx 100mm in length, and wind onto the spindle (what you’re calling the shaft) in a clockwise direction, and push into the void. Using the gland nut push and turn clockwise to re-engage onto tap body. If you struggle with some of this, turn the stopcock clockwise a little until you can feel it engaging on the thread. Once this is done, nip up with a spanner and all should be ok. I mentioned the outside stopcock incase anything goes awry.
Thanks very much for your reply! I will give that a go! Sounds really simple and I've redone all the pipework in the kitchen anyway, so I should be able to cope with more PTFE tape, wonderful stuff.
If you want it in detail:

To fix a leaking gland nut on a stop valve:

1. Close the valve completely. Turn clockwise looking down on the handle.
2. Undo the gland nut. This is the small nut, usually hexagonal but occasionally a knurled ring.
3. If the “T” piece for the handle is screwed on in the centre, try and loosen the screw.
4. If possible, remove the handle and the gland nut. If not possible, carry out 6 and 7 below as far as you can.
5. Clean any limescale from the shaft of the tap as far as possible. Use a limescale remover like Kilrock if possible. For any remainder, use fine sandpaper (120 grit or greater) or a fine file.
6. Clean the shaft as much as possible, and make sure there is no roughness to it. A polish with grade 00 wire wool or Brasso is good.
7. Cut a length of PTFE tape. Start with about 10 inches / 250 mm. Twist it into a “string”
8. Wrap the string around the spindle, clockwise looking down from the handle end.
9. Put the gland nut back on the spindle if removed.
10. Push the PTFE down into the body of the tap with something like a thin flat bladed screwdriver.
11. Screw the gland nut back into the body of the valve.
12. Tighten the gland nut so that the spindle can just be turned by hand (with the handle back on if removed).
13. Open the valve and check for leaks.
14. For a slight weep, try tightening the gland nut a little more.
15. For a more serious weep, repeat as above and use more PTFE.
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Many thanks, oldbuffer! I have printed out your instructions and will have a go at it tomorrow, very helpful.
I like to pack the gland with vaseline or silicone grease when winding the ptfe in....helps with the packing a bit.
John :)
I'd like to say a big THANKS to you all, I fixed it in five minutes yesterday - didn't need to turn off the water mains stopcock, I undid the gland nut, twisted 10 inches of PTFE into a string and wound it round the spindle clockwise, pushed it in with a flat headed screwdriver, did up the gland nut again, and ran half a bath of water to make sure there were no leaks at the stopcock, and it was dry as a bone! And if it ever goes wrong I've printed out this thread and have a copy to refer to, thank you all so much!
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