Unusual copper pipe size

I think you'll be lucky on a Sunday, it sounds more like aircon or refrigeration pipe.

Bash the pipe flat with a hammer, fold the end over, squash in a vice or with mole grips and solder it up - mum and dad's house had several such "points" where they couldn't afford a full set of radiators straight away!

Threaded pipe is sized by the thread that will be cut on it. What you have found is almost certainly 3/8" pipe with 3/8 BSP x 19 tpi threads. toolsatan have a range of adaptors and will be open on Sunday. Possibly best to get up to 1/2 bsp thread male and then into 15mm compression fitting unless they do a 3/8 x 15mm adaptor.

Correction: It looks like toolsatan have dropped 3/8 bsp adaptors and now only carry 1/4 and 1/2" in the smaller sizes.

Screwfix have a 3/8 to 1/2 inch bush that would probably do for starters?

Looking it up, I'm sure you're right, thanks. Beats me how 3/8 can be bigger than 15mm but I'm sure there's a rational explanation somewhere!

Now the challenge will be to unscrew the pipe, which didn't want to move this afternoon. Maybe I need some bigger stilsons (and a way to hold the rest steady).

Thanks - looks like that would make a start to get to a standard size.

In article , Chris French writes

Well spotted :-)

Also, I'd recommend a liquid sealant for thread jointing lots of interdependent threads in close proximity, less to go wrong:

On 14/02/2015 19:07, GMM wrote: ...

I have only come across threaded copper pipe in a domestic installation once, and iirc the thread was rather finer than 3/8 BSP, which is 19 threads/inch. This was in my parents' house in Derby, and when I called in the local old-style plumber's merchant, they explained that one particular local builder had used them in the 30s. They'd had end-feed couplers made to convert it to 15mm.

This is all of no help whatsoever to you, because they're long gone. I have used, but can't find again, one of the adaptors sold for converting early plastic pipes to standard sizes. These come with various inserts and sealing rings. I thought it was from BES, but their impenetrable website has prevented it from leaping out.

Not much help there then, either.

I tried.

Kevin

Yes, indeed. The *actual* size of all BSP fittings is considerably bigger than the *apparent* size because the latter is the nominal bore size - to which you have to add the wall thickness. You can find a table of BSP sizes here:

Squash the end flat and solder it...

You can get universal transition fittings designed to connect things to odd pipe sizes:

With 3/8 ID copper you could also probably just flare the end a bit and stick some 15mm into the socket created and solder it.

You won't find the bore sizes match the nominal size either. When the BSP threads were designed, pipes up to 3" bore were wrought iron and those of 3" and above were cast iron. Steel pipe could have thinner walls, but the OD had to stay the same to take the BSP thread, so the actual bore sizes increased. Plastic pipe bores also vary according to their pressure rating, but the OD stays the same.

In the sense that 3/8" is about 9mm, it clearly isn't bigger than 15mm. But in the context being discussed here - 3/8 BSP - the 3/8 refers to to the ID but the OD is about 16.6mm which *is* bigger than 15mm!

You might get an 8 x 15 mm end feed reducer to fit. The 8mm end should be about 3/8 external.

Indeed. That's why I wrote *nominal* bore. Any resemblance to *actual* bore is entirely coincidental!

But 15mm tube (external diameter).

Simple.