Now look at the second picture, showing a really interesting "wiring" of the pipes.
In Sweden, it is illegal to join or branch two pressurised water pipes inside a wall All joins and branches, whether soldered, flanged, press-fit or threaded, regardless of pipe material, must be out in the open. And for good reasons, it seems.
Drains, OTOH, are OK; a lot of waste water piping is done with gasketed HDPE pipe, and that's OK to run in concrete or otherwise inside a wall.