Joining 1/2"BSP to 15mm

[Angus]

Does anyone recognise the coupler in the photo? The pipe is the mains coming up into the flat. I aim to replace all the plumbing with 15mm plastic but I'm concerned about leaks where it joins the mains. I'm thinking of removing the existing coupler and putting a speedfit 15mm to 1/2BSP tap connector onto the male thread (on the bottom pipe). However this pipe is probably 60-70 years old so I'm a bit concerned that I'll find that the male thread end is a bit corroded and hard to get a good seal on, and for that reason I'm considering leaving the coupler on and trying to unscrew the upper pipe so that I can then screw a male to male brass nipple into the top of the coupler (which, being female and thicker, may have suffered less corrosion) onto which I can then attach my tap connector. (Another option would be to attach a Philmac PE x Copper /PEX joiner to the female thread at the top of the coupler). However I don't know how this old coupler works - perhaps there's nothing to screw into. Any ideas, tips or alternative strategies? I've thought about dielectrical corrosion but from my research it seems that brass to galvanised iron is as good as anything.
Many thanks in advance.

 

[Angus]

Here's the photo I meant to send.

 

[sheff paul]

Here's the photo I meant to send.View attachment 22996

Bang on a Yorkshire no 2 ,with a bit of locktite on it,cant tell if its 1/2 or 3/4 thread from the photo,that will bring it to copper... Doe's that 'Dielecrtical' play for Chelsea or Man u

 

[Chalked]

That fitting us called a "long thread" I would try and leave the socket on and remove the top piece of steel. Then use a male adaptor. You will find that the female steel thread will be in better condition.

 

[Chalked]

That fitting us called a "long thread" I would try and leave the socket on and remove the top piece of steel. Then use a male adaptor. You will find that the female steel thread will be in better condition.

Ps hold against the socket when undoing the pipe to stop it breaking the seal and the nut at the bottom is not connected to the socket.

 

[jonnyswamp]

Agree with all that Chalked has already said
If though there is any problem with the female thread on the coupler, or if you can't undo the top pipe you could cut the bottom pipe just below the nut leaving about 20mm of thread
this can be joined with a 1/2" (or whatever size the pipe is) female iron to 15mm (or 22mm if 3/4")
This way, the 20mm of thread will be tapered so should make a good joint

 

[Angus]

Thanks. I'll try to remove the upper piping to reveal the upper female thread, as you suggest. The outer diameter of the pipe, according to my measurements, is 21.3mm, which I understand to be 1/2"BSP, so I presume I need something like a Center straight compression male iron (spigot) tapered thread connector 15mm x 3/4inch. Only I guess it needs to be 15mm x 1/2inch - though I have to say the 3/4 inch looks more compatible to the eye, ie 21mm being closer to 3/4" than 1/2".

Would the female top end of the long thread be tapered as well? Can/should you go tapered to tapered? I assume a straight brass thread is not a good idea.

PS I'm not sure what a Yorkshire no 2 is (sounds whiffy..) - I can't find it on the net -but I'm looking at a compression fitting cos the stop-cock doesn't work 100% so slight drip.

 

[Angus]

That's another very good idea / plan B, thanks! Still wondering, do I go tapered to tapered or, in this case, straight female to BSP tapered?

 

[jonnyswamp]

You should be fine as long as one of them is tapered

 

[Eric withy]

Pipe and fittings long screwed and back nut used before unions made for all sizes personally I would cut pipe to where I needed to connect 2 choices cut new thread in situ or cut and use a promo fit ie Johnson coupling hope that helps you out

 

[Angus]

Many thanks to all for your replies - what a great forum. I'll report back after I've attempted it, in a few days.

 

[Angus]

Forgot to report back.....so, the results: I managed to unscrew the 1/2" pipe out of the female socket without disturbing her (thanks, no doubt, to the tip about gripping the socket/'long thread' and not the nut below it). The thread looked as good as the day it was put in (1950s?). Next step was to screw in a 1/2" to 15mm coupler. I had two types - parallel and tapered. I couldn't bear to damage the thread on the iron socket with the tapered coupler, so went for the parallel one, even though it wasn't DZR brass (which the tapered one was), DZR, according to my research, offering a better dielectric union. Time will tell if that was a mistake! I used some Loctite 55, screwed it in - nice snug fit, no leaks, success!

 

[snowhead]

The end of sleepless nights for me worrying about whether you fixed it or not!!

Thanks for updating.

 

[Angus]

Ha ha!