leaking stopcock nut-help with pipe sizes please!

2 Mar 2004
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United Kingdom
hello folks,to start with i apologise in advance for my numpty question and my lack of knowledge,but i guess that's why you guys are here.
I have a leaking nut! The main cold water feed coming up under my kitchen sink is a large (28mm?? a 22mm olive won't fit over) thick blue plastic pipe and has a brass stopcock attached to it,leading up from the top of the stopcock is more of the same blue pipe attached to the stopcock with a large blue plastic nut,further up there is a weird reducing fitting (push fitting on the blue plastic pipe side/compression fitting to grey 15mm plastic pipe) which leads up to a brass T compression fitting which branches off to the washing machine and my sink. After discovering water all over my kitchen floor i sourced the leak back to the big blue plastic nut,after shutting down the water from the outside stopcock i removed Big Blue Nut using some swanneck pliers,wrapped PTFE tape around the thread of the stopcock and up the pipe around the olive and rubber washer and replaced the whole lot. I turned the water back on and i'm still leaking at the base of Big Blue Nut,it also seems to have a split in it as there is a very fine jet of water. Is there a brass compression reducing fitting that i can use to get rid of all the plastic pipework and replace with standard 15mm copper pipe up to the compression T fitting? Sorry for my long winded explanation but as you can tell, i'm no plumber and without uploading a photo i thought i'd try to give the full picture. My house is less than a year old so i'm guessing that metric size pipes have been used. Please help as i'm getting pi**ed off with getting wet feet! Thanks,
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The pipe is 25mm mdpe. Not sure what you mean by a nut, which seems to be alone?? Perhaps you can find a pic in a cat?
Thanks Chris,
the leaking "nut" is the one that is attaching the 25mm MDPE pipe to the top of the brass stopcock. Should i just get a replacement "nut" rather than trying to replace the whole thing with 15mm copper pipe?
Oh I see. I expect you'll have to buy a new stopcock to get the right nut. No standard on threads :cry:
Could try taking one from a cheaper fitting if you can see a make.
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Couple of years back I fitted a new stop cock purchased from B & Q.
The inlet side was for 25mm blue MDPE (using a steel insert) The outlet side was for 15mm compression. Both nuts were brass.
Thanks for your help and replies guys but sadly it's all too late as i am now sitting in a house without water,on returning from work it was still dripping,stupidly i slightly overtightened the offending blue nut which promptly split sending mains pressure water all over me and the rest of my kitchen. So it's now down to my landlord,who bodged the thing in the first place,to fix the thing! Good luck to him i say,i took photos and showed the guys at my local Plumbing Trade Supplies who were completely mystified by his whole set up and couldn't supply the parts i thought i needed. Ill let you know the outcome!

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