How do I extend a 21.5mm OD black pipe for external water supply?

[Nell Boase]

Hello!
Have had a hunt for similar threads, but think I might still need help identifying a black pipe and how to fit a stopcock to it.

I've got pipe going to an external tap. It's black, flexible plastic and was probably installed 10 years ago. It's 21.5mm OD (measured several times with callipers, definitely not 20mm or 25mm). I assumed it was some kind of MDPE, but having measured it, I'm now not sure.

I want to cut it and insert a stopcock, and a tee to take a supply away to install a tap 30m away in the field (have already dug the trench).
Was planning to use 25mm blue MDPE and a pushfit 22x25mm stoptap plus equal tee. But I am a total newbie, and now worried that I won't be able to make a seal (there's no other stopcock between the tap and our main water supply).

Seen suggestions that it might be black alkathene with a 3/4" outer diameter, but that seems unlikely as installed around 2012.
But I can't cut it to check the internal bore without having a means of sealing it so I can eventually turn our water supply back on.

Would be super grateful for any suggestions....

 

[Doghouse Riley]

Hi and welcome.

I suggest you go to a plumbers' merchants and ask for some "professional advice." That always gets helpful suggestions. Thirty-five years ago I wanted to fit a basin with a hot and cold water supply in our garage, so I needed to fit a supply from a spur on the tap outside our kitchen window and did just that.

I have a blue (painted black) alkathene pipe connected to the spur and it runs under the drive to the garage where it connects to ordinary copper pipe and then to the tap on the basin.
They supplied everything I needed for both ends. Too long ago to remember what were the individual connections. So I took a photo this morning. You can see there's a few "bits." The copper pipe is at the top left corner of the photo and you can just see the alkathene at the bottom. It was quite an easy fix.

 

[Nell Boase]

Hey doghouse,
Thanks v much for the post and pic. We’re rich in screwfix and toolstation round here, but short of trad plumber merchants — makes it hard as mostly it’s just me and someone similarly amateur leafing through the catalogue :-(. And my excellent plumber is mad busy at the mo.
I’ve found a Plasson “universal” coupling that says it can cope with 15-22mm (connecting to 25mm). But will hunt further afield for a good plumber’s merchant….

 

[Doghouse Riley]

Hey doghouse,
Thanks v much for the post and pic. We’re rich in screwfix and toolstation round here, but short of trad plumber merchants — makes it hard as mostly it’s just me and someone similarly amateur leafing through the catalogue :-(. And my excellent plumber is mad busy at the mo.
I’ve found a Plasson “universal” coupling that says it can cope with 15-22mm (connecting to 25mm). But will hunt further afield for a good plumber’s merchant….

This is the firm I've used for decades, the counter staff are very knowledgeable.

Home

bathroom showroom manchester northwest Sale Cheshire plumbing heating

www.jcquirk.co.uk

 

[Nell Boase]

thank you!

 

[Nell Boase]

In case others search this later: The plasson universal coupling worked great. I very lightly sanded the black pipe (circular NOT lengthwise) to remove scratches and old limescale. Top tip: DO mark the pipe before you insert it so that you know it has gone in far enough, as you can’t pull out a partial insertion to check!
Completed join, plus stopcock, garden tap, and elbow off to take further up the field in photo: