Imperial Waterpipe Sizes

[badlad.biz]

I have a 1980's built house with what I think is supplied by a 1/2" Alcathene pipe. Its black plastic and measures 21.5mm outside diameter. It fits onto a Stopcock and then becomes Copper which measures 22.02mm outside diameter.
The stopcock leaks and needs replacing, but my local DIY shop says there is no such size as 1/2" Alcathene/Plastic and it has to be 3/4". A stopcock of this size looks huge and I'm sure its wrong.
Is there such a thing as 1/2" Alcathine and will it fit a 22mm Stopcock is my question?
Any help would be appreceated. Thx

[scotman]

There was a 1/2" size plastic pipe once. I reckon that with 3mm nominal wall thickness it would be about 19mm outside diameter.
I seem to recall that copper pipe with OD of 22mm is the metric equivalent of the old 3/4" size.

[The Builder]

Shopman speak with forked tongue, badders ................... not only was there a 1/2" alcathene, but a 3/8" as well. To make it wonderfully complicated, there were several densities as well. (Different pipe wall thicknesses.)

You need a proper plumbers merchants, or a Farmer's store. Fittings like this are mainly used now:

http://www.screwfix.c...-stop-cock-20mm/37602

[badlad.biz]

Ok, Its off to town with my vernieer guage to measure all the fittings. I was kind of hoping I might be able to buy a 22mm compression stopcock to fit as its what it looks like from your screwfix catalogue.
Badlad.

[The Builder]

Easier than that Badders, that pic was just for illustration......... in practice, you buy the stopcock plus plastic adaptors and inserts to fit the ends that you have to connect to.

Any chance of cutting off a bit of the two ends to take to the merchant's?

[badlad.biz]

Thats another problem. The pipe comes up through the concrete and is only 2" long. Plus, its behind a Kitchen Cabinet. Life is never easy. I'm going to be busy this Easter.

[scotman]

Should have asked earlier; where is the stop-cock leaking from? Also, is it plastic as shown in the picture posted by Builder or metal like this image?

http://www.screwfix.c...rs-4.1/&company=ae235

If it is metal and leaking around the operating knob that can sometimes be fixed by tightening up the small nut on the top. If it is leaking where the pipe(s) enter that can also sometimes be fixed by tightening the fixings. I am not familiar with the plastic ones.

[badlad.biz]

Well Scotman, Your picture shows exactly what mine looks like, but do you think the threads will fit. For Info the valve is leaking from the stem because the bit it screws into is split. I dare hardly look at it as it looks as if it might just fall apart, and I havent found the stopcock outside yet.

[scotman]

Before anything else happens you need to find the main stop valve in the street outside as you have to shut this before removing the stop-cock in your property. If the body is split as you say it will have to be replaced.
Just to make things absolutely clear here - I understand from your posts that you have a plastic inlet pipe which connects to your metal stop-cock and then continues inside your property in copper pipe with sizes as you have already given. Is this correct?
If the access is difficult and the exposed length of the available plastic pipe is short I would seriously consider getting a plumber to look at this.
Are you intending to replace your stop-cock with similar metal one or use plastic similar to the picture posted by Builder?

[scoob101]

It sounds like old polypipe which they used to use before MDPE (alkathene), most plumbers merchants will supply an adaptor to fit this.