Properly dimension drinking water pipes.

§ 12 (2) of the AVB-WasserV, the installation and significant modifications may only be carried out by installer companies registered in the installer directory of a WVU.

As said, no plaintiff, no judge.

Oh dear oh dear, I think I will keep looking for a heating engineer who would do it for me.

The Federal Environment Agency should editorially revise its publication ... (Mein Vater hat vor ca. 15 Jahren offenbar gegen eine Ordnungswidrigkeit begangen.)

The German Environment Agency should editorially revise its publication ... (My father apparently committed an administrative offense about 15 years ago.)

I am pretty sure that he is not the only one who laid his pipes himself; in my opinion, there is not much to it.

Take a look at an aluminum composite pipe. Often also called PEX. Anyone can do it themselves with that. Just use a few screw clamp fittings. Holds great.

I don't think that bodily injury is still a regulatory offense. If a corresponding personal injury occurs due to a Legionella infestation, it's no longer a trivial matter.

As I said, where there is no plaintiff, there is no judge. But as soon as you get involved with renting, it can really get nasty.

Besides, it's up to everyone to decide what they do. Personally, I have no problem doing something like that myself as long as it only affects me and my immediate surroundings, that's certainly OK, but since I mostly rent out the renovated properties, it becomes a different matter and that's why the note.

By the way, you can skip using aluminum composite pipes in sanitary installation; that's only interesting for heating because it's about oxygen tightness there. I would take a normal 20 or 25 plastic pipe, it's easier to install and thereby build a loop.