Where to branch out of 15mm hot water

[MorganL]

We have just got a top end boiler, and are ready to ditch the electric shower. As such I now need to put in a hot water supply to the shower which is currently only cold only. We have no problems with water pressure which is pretty epic since we got rid of the water bottle.

here is a (cough) roughy diagram of the existing hot water system with flow direction.. it’s currently doing very little, one Bath, one sink and a (new) downstairs sink for an under stair toilet.

15mm copper pipe, copper t junctions. The blue line is where copper has switched to the plastic pipe (route to downstairs basin was epic) with a plastic connector. My question is this

for the new shower hot supply should I
1) put in a T off the main copper pipe before the sink and after existing T or
2) can I replace the plastic connector which is a 1:1 connect copper to plastic with a plastic 1:2 connection T and branch off to the shower from that point, a branch off a branch so to speak

1 requires cutting, new T joint in main copper line
2 requires almost no cutting, just replace a connector, new a new pipe for the shower

the distances are negligible and there is not much chance of sink / Bath / shower being used together (only 2 of us in the house). There is a tiny chance downstairs hot tap may be briefly used at same time as shower

 

[terryplumb]

You can join into the copper pipe wherever you wish,and continue in copper to the shower. Plastic pipe has smaller interior bore and restrictive pipe stiffeners ,ok for basins ,but for showers and baths stick to copper.

 

[Madrab]

IMO, depending on pipe run lengths then you shouldn't have any issues converting the straight coupler into a Tee and then run that to the shower. Even then if you have good water pressure and flow then you shouldn't have an issue.

You will see a drop off in HW if another hot outlet is opened though, it's just the way combi's work unfortunately.