ᐅ Design of Drinking Water Installation Renovation

Hello everyone,

I am currently renovating our detached house built in 1984. Two bathrooms in particular will be completely renewed, and the drinking water installation (previously copper piping) will be replaced with composite plastic pipes up to the basement. I would like to handle the planning and installation myself (the Viega Raxofix press-fitting system, etc. is available). The following points have been important to me in the design:

1. Orientation according to the current state of the art for drinking water hygiene >> no dead-end branches and adherence to the 3-liter rule;
2. The installation should be feasible with minimal remodeling >> therefore, a full hot water circulation system is ruled out; I plan to use floor-level circulation and branch lines on each floor;

My current design is as follows:

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Cold Water Pipe Network

Design according to DIN EN 806-3

Question 1: The standard specifies a maximum pipe length of 5 m (16 ft) for sections 3 and 10. Are 5.9 m (19 ft) and 8 m (26 ft) still acceptable?
Question 2: For section 8 (start of the riser), my calculation suggests an inner diameter of 20 mm (26 x 3 mm), but I would prefer to use only two different pipe dimensions. Is it feasible to use the 20 mm (3/4 inch) pipe at the beginning?



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Hot Water Pipe Network

Design according to DIN EN 806-3 (despite circulation)

Question 1: The standard demands an inner diameter of 14 mm (18 x 2 mm) for section 4. Would it still work to keep the 20 mm (3/4 inch) pipe all the way to the shower?
Question 2: The standard refers to DN10 circulation pipes. Should I rather use these, or stick with 16 x 2 mm pipes?
Question 3: According to my calculation, a 16 x 2 mm pipe is sufficient for the riser from ground to upper floor (section 2). Should the pipe diameter reduction take place already on the ground floor or only on the upper floor (as shown in the pipe network)?

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I would appreciate your general feedback on the design and the questions above. Thank you!

When it comes to water, gas, and electricity, amateurs should not get involved; this is a job for professionals. This is also specified in your utility provider’s technical connection conditions (TAB) due to drinking water hygiene requirements.

Thank you. Does anyone have any technical advice?