Properly dimension drinking water pipes.

Hello everyone,

since I want to move into my newly purchased property in 3 months and not a single heating engineer has time to lay the new drinking water pipes for me, I thought about doing it myself.

Stainless steel pipes with a price system will be used.
Heating will be redone by the heating engineer.

But since I have little knowledge about the dimensioning, I turn to you.

It is a bungalow. The bathroom is below the bathroom, which means I will run the pipes up along the wall on the left and right and connect there with washbasin and WC, and on the other side tub with shower, then through the wall with kitchen sink and dishwasher. Actually not complicated, but how big should the pipes be?

I attached a picture, what do you think?
Is 18 mm hot water sufficient for circulation ?
18mm cold water pipe for washing machine?
15mm cold water pipe for dishwasher?

I would be very grateful for any advice from you.

Bold to size that yourself. Doesn't that also depend on water pressure, pipe lengths, heights, etc.?

Also, it would be too risky for me to make the connections myself. Water damage can be costly ...

I believe that sizing is not the difficult part... but doing it yourself? Is that allowed? I wouldn’t do it.

Why shouldn't one be allowed to do that themselves? I would also better keep my hands off the fuse box, but water pipes?

I believe sizing is not the difficult part... but doing it yourself? Are you allowed to do that? I wouldn't do it.

Without knowing the location of the pipes and thus the number of outlets, it's hard to say anything about it. The circulation pipes for hot water are executed as 3/4 inch here (the shower and sink are connected in series), the cold water pipes as well. But they also run completely through the house.
As a single pipe for a dishwasher or washing machine, 15 mm (what is that, 1/2 inch?) is certainly sufficient.

Best regards,

Andreas

So the way you drew it, it won't work.

Hot water:
On the one hand, you need to avoid branch lines because of the risk of legionella; on the other hand, you basically have a parallel circuit of loops where the hot water then takes the shortest path. Run all consumers ring-shaped from your buffer. This has two advantages: 1. you can reduce the cross-section because the water can run through 'both' pipes if necessary, and 2. this prevents branch lines. There are special fittings that have 2 connections, or if you absolutely want to use stainless steel, insert a T-piece a few centimeters before.

Cold water:
Basically the same applies as for the hot water. A ring would be optimal, but if not possible, avoid branch lines and connect the consumers one after the other. The toilet should be the last consumption point. This ensures that the pipes are always 'flushed' and no 'rotten spots' develop due to lack of use.

Besides, the previous speakers are right. According to the drinking water ordinance, it is actually not permitted to lay water pipes yourself in the house. As long as nothing happens, no one cares, but if something does happen, there could be problems. And I'm not talking about water damage here but about personal injury.

Besides, the previous speakers are right. Actually, according to the drinking water ordinance, it is not permitted to lay water pipes in the house yourself.

Can you back that up with a quote? The Federal Environment Agency has a brochure (also freely available as a PDF on the internet) entitled "Rund um das Trinkwasser". It only recommends having work on the drinking water supply in the house carried out by a professional company.

Note: Of course, the work must be carried out professionally, but if this condition is met, then in my opinion, one may also do it oneself; INAL.