3/4” Class D pipe, what to do?

[SolRobinson]

Hiya, looking for a bit of advice. I was told when I had a plumber round at my property when I first purchased it that we were on a galvanised or lead pipe mains supply. Not really knowing what those looked like, I trusted that the dirty black pipe was what he said it was.
I’ve ended up applying and being accepted to our water suppliers lead pipe replacement scheme, so we had planned to lay the new blue MDPE.
I came to do some work on the water main yesterday (fit a new temp stopcock as current one leaks) and I’ve found that the pipe is the old imperial black plastic pipe.
I turned the water off at the boundary stopcock and went to plumbers merchant with an cut of the pipe and they’ve said it’s 3/4” class D pipe. It’s roughly 22mm with an internal diameter of about 15mm. They gave me a 22mm straight coupler with a brass 3/4” olive, which I’ve now temporarily connected to some 25mm MDPE, with a stopcock going to 15mm copper & drain off.

- I’m now kind of stuck on what to do and would like some advice.
Is this stuff worth ripping out and replacing with blue pipe? I know 25mm plastic would be better flow than 15mm plastic, but is there any other downside? I’m not even sure if the water company will replace the pipe now.
- Is it even worth messing around with my 25mm MDPE or should I just go straight from this 22mm into 15mm copper.

 

[Exedon]

What you have is 1/2 in alkathene it may be class D more likely class C.
Either way using a 22mm compression connector and 3/4 olive it needs a pipe insert, if it's class C a short length of 15mm copper with end flanged will do nicely,
If its class D I wish you luck!
As for replacement if it were mine I would.
Alkathene pipe was always/is gas permeable so had to be laid well clear of gas pipes and drains .
For health reasons it was changed to the current m d p e.

 

[ianmcd]

As @Exedon says you have Alkathene horrible stuff replace it, doubt if you will get a grant to get rid of it though, your water supplier might pretend it was lead to get the business,

 

[SolRobinson]

Thanks for the advice! Not sure we have the budget to be replacing the whole thing without the grant from the water supplier.

I've got a question about earthing & bonding then. I plan to run a 20ish meter length of 22mm speedfit PEX (no joins ) from where the water mains comes in, to the bathroom at the opposite side of the house and then drop it down into the kitchen (below the bathroom)
The old water mains came into the garage, ran along the floor, into the kitchen to the stopcock. After the stopcock was the earthing cables running back to the consumer unit in the garage. If I'm now going from plastic water mains, to plastic pipe (1 tee off to copper pipe for boiler feed) where do I put my earth? Cause as I understand it, anything after plastic isn't effective...