What is this 14mm/20mm pipework?

[ABCwarrior]

Our house has been cursed with this stuff, and I'm installing a shower in the downstairs shower room/toilet directly below the bathroom above, and need to run a pipe from here down through the floor/ceiling to the shower below.
I've drilled the hole which will take the pipe through, all gone well, but to avoid cutting this hideous stuff that needs hammered in inserts etc, I'm planning to remove the section between the one that feeds the cistern above- ie it runs through an isolator valve, I'm planning to remove this section from the valve to the cistern and replace it with JG Speedfit with a T from this running down to the shower. Would that be ok? Or if someone flushes the upstairs toilet will it significantly reduce the flow to the shower? We've got 3 bar static pressure btw.

 

[muggles]

It will work but it would be much better to run it off the main run. No idea what kind of pipe you're talking about though, are you able to post a picture? Static pressure means naff-all, it's working pressure that's important.

 

[ABCwarrior]

The main run branches off first to the cold tap, then the cistern, and then terminates at the cold supply to the bath.
One of the problems is that the main feed pipe(same diameter anyway) is close to the floor and even getting to it would be a nightmare- it's in a boxed off section, can barely reach it and can't climb in it.
Hence the reason to replace the pipe from the cistern isolator to the cistern, this I can get to easily as it's at the top of the boxed off bit.

I'm sure the pipe sizes are some euro crap...why they didn't stick to 15/22 I'll never know....

 

[Charnwood]

There are some weird and wonderful sizes coming out of the woodwork nowadays, generall on crimp-type fittings systems. Pegler Yorkshire's Henco range, for instance; 16, 20, 26mm etc.

 

[ABCwarrior]

Aye, it's got those stupid crimp things on it too. Last winter a plumber mate re-did the whole downstairs to get the pipes all above FFL to stop them feezing, I had to do an 80mile round trip on Hogmanay to get the inserts etc to be able to mate this crap to conventional UK isolators etc...