Ok, will need to replace the mains stopcock in the house (classic scenario, try turning it off, gets very stiff, water still not stopped, then an ominous loosening of the shaft and water starts flowing again....)
The stopcock is BSP threaded rather than compression (which was rather annoying as it meant I couldn't pick one up yesterday afternoon from Screwfix).
A couple of quick questions
Assume that BSP threads are sized by the diameter of the male part - in this case a 3/4 inch steel pipe incoming main.
do I need to seal the thread with anything as well?
On a plumbing aside, and reason for tuning off the stop c*ck. Why might a copper pipe develop a tiny pinprick hole (pipe maybe 25 years old?, Cambridgeshire, very hard water area)
Some years ago I remember having to change a friend's DHW cylinder as the top dome had become porous. It seemed as if the copper had some minute contaminates (perhaps zinc or somesuch) that had eventually corroded away leaving invisible holes in the copper.
No. The size is the bore of the wrought iron or, for 3" and above, cast iron pipe that the thread was originally cut onto, so there is no obvious relationship between the pipe OD and the BSP thread size.
This table from my web site may help:
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would guess from what you say that the thread is 1/2" BSP.
The thread is probably a parallel BSP thread, in which case it will need sealing. I like PTFE paste, but PTFE tape is probably easier for most people.
Problem is that directly above the stopcock there is a T. One running up to feed the WC, one running horizontally to the rest of the supply. To put another stopcock in means replumbing this. Do able of course, but I'm minded to try to removed it first. Also I'm concerned that the stopcock might now be a partial restriction to the water flow.
There is a stopcock outside by the meter, so not a problem dealing with water flowing. Not entirely sure what has happened inside the valve. It got very stiff, but water still flowed. Used a spanner to give some more leverage to carefully shut it some more, then at some point I felt it get easier, as if the shaft was shearing off or something. Then water started flowing out of the tap more so I stopped :-) Presumably the bit that cuts off the water has sheared off and been pushed back out of the way by the water pressure.
I thought De-zincification was an issue in soft water areas?
any other suggestions to make the job easier Harry :-)
A drive paved with pattern imprinted concrete, and no desire to spend a couple of grand replacing the pipe isn't really a path we want to go down right now.
Can't say as any of the other fittings in the house show any symptoms
My house was originally fed with a steel pipe from the farm across the road. At some point this was replaced (pre WW2) by a non-metered supply from a different direction at a better pressure. During the house renovation the steel pipe was in the way and had to be dealt with - it was still live and apart from turning off the farm briefly to deal with it, I did find a join which came undone without any problem at all so that it could be capped.
Nothing on a "3/4" BSP" pipe or fitting actually measures 3/4". the "3/4" refers the bore (inside diameter) of the original standard pipes, but the standard bore was later increased so it is a bit bigger than 3/4".
Ok. first of all as other posters have said, this will be 1/2" BSP. This is good, as larger and smaller sizes tend to be more difficult to find, though any BSP fittings can require you to order something in rather than picking up from Screwfix or wherever.
Before going too far along the road of replacing the stopcock, it may be worth seeing if you can dismantle it in situ and look at the washer and the moving parts - if there's something obvious there it may be possible to put it right without going to the trouble of removing the main body of the stopcock. Be very careful when unscrewing it, obviously - you don't want to have to leave it turned off while you go to find the parts to fix it!
The big problem in removing the stopcock is of course that - unless the pipe on one side or the other is free to rotate - in trying to unscrew one pipe you're tightening the other. Installers use a couple of methods to get around this, such as unions (for example see
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- down at the bottom of the page) or longscrews (don't have a picture of this at the moment - will try to find something if needed). If they haven't done this, but have just started at one end then assembled one piece after another it makes things more difficult - I'm assuming you wouldn't want to try to reverse this assembly method. A picture or two would help us to know what your situation is. Even if you can unscrew the stopcock, of course, you may hit the problem that the new one isn't quite the same length... What I've seen done most frequently in this situation is the following
- presumably because not all plumbers have the equipment to thread the ends of steel pipes, and it's easier to do -
1: Locate points upstream and downstream of the bit you want to replace where the pipe is screwed into a socket, tee or bend.
2: Hacksaw through the pipe and unscrew these joints.
3: screw in a BSP to copper adaptor in each position
4: Replace the bit in between in copper
When I had to replace my stopcock it was a similar excercise but using lead to copper adaptors - the original was soldered to the pipe with wiped joints. It was a more urgent exercise than I should have liked - after failing to turn fully off, the flow did not increase beyond a trickle when I tried to turn it on again. This proved to be because the jumper that carried the washer had managed to break and then make its way round the corner to lodge just before the solder joint
I'm pretty certain something inside has broken and would need replacing. I'm not confident I could find inards to put inside a 30, 40 who knows how old stopcock
AFAICT under the paint, the copper is joined to the stopcock via a compression to 1/2" BSP fitting. (Hopefully - it may well not work our like that - this can be loosened and unscrewed from the stopcock
Piccie here:
There is enough leeway to move the pipe up/down a bit if necessary. The horizontal pipe runs for a couple of metres or more before getting to another junction. The one going vertical has a a horizontal section further up (it feeds a WC cistern) which could be bent a bit as well.
If it's just the jumper (the piece with the washer on it that's pushed against the seat) then it's likely you could find that quite easily: if it's anything else I'd agree that without a big box of spares collected from old systems you're probably stuffed on that one. I suspect you'll find it worth unscrewing the works from the body anyway to make it possible to rotate the stopcock without gouging the plaster, so I'd still think it might be worth examining at that stage to see if you can get away with just replacing the jumper.
That makes it much clearer - I'd assumed somehow that the change to copper came at a later stage. Looking at the picture I think I might well change to having the BSP to copper connector just before the new stopcock.
That's a gunbarrel tap body and is easily replaceable with a gunbarrel lever valve. Unscrew what's above it, get molies on the bottom iron pip and unscrew the tap body. Bob's yer faintly-smelling-of-wee strange uncle.
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