Old leaky 1/2" system - compatibility with metric parts

Hi,

Wondering if anyone can help.

Ive got an old 1/2" system but have a leak.

One of my options is to fit a blank nut.

Is it ok to fit a 15mm blank nut to a 1/2" joint?

 

Yes - the sizes are close enough

 

If you mean put a blank capnut or cap on a 1/2" compression fitting, the threads are both 1/2" BSP, so yes it is OK.
You will need to fit either a rubber or fibre washer in it.

 

not all the threads on old 1/2" compression fittings are the same "prestex" for example

 

hi, can you expand on what you mean by this.
(the current nut has prestex on it and im not sure if this is a specification, manufacture or what.

 

wont this come with it?

 

The old half inch " Prestex" compression fittings had more threads per inch,

finer threads than 1/2" BSP.

 

A rubber washer should come with a blank capnut, but a brass cap will not have one.

 

Prestex is the brand name of compression fittings made by Pegler (now Pegler Yorkshire.

If, as Jim says, their older fittings had a b'stard thread you will struggle to find a capnut to fit.

You could try a blanking disk, but you'll only find them in 15mm.

 

A photo and a discription would be a help Daz

 

thanks.
whats the difference between a blank nut and a blanking disc and why would you use one instead of the other?

 

would you expect there to be an olive with a prestex joint? I think my problem is there is no olive.

and do i need a special prestex olive? if not what kind do i need?

 

Prestex is a brand of compression fittings made by Pegler.

They used to do both Type A and type B joints, but now only do Type A.

Type A:

Type B, where the pipe is swaged or belled out:

Blanking disc, as shown above, goes into a fitting, replacing the olive.
Blank capnut replaces the olive and nut, and should come with a rubber washer.
Blank capnut. This is conex's fig. 63b:

 

is it possible to put too much pfte tape on?

ive wrapped it around the thread, where the pipe goes into the joint and about 5mm above that

 

Yes, it is, and "ive wrapped it around the thread, where the pipe goes into the joint and about 5mm above that" is.
A bit round the olive should suffice, although no manufacturer I know recommends using PTFE on a compression joint.

 

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