Cistern and water extraction

Hello,

I have been thinking about rainwater use. I have approximately 185 sqm of roof area and about 275 sqm of green space. We would like to use the rainwater for garden irrigation and cleaning. I have attached the outdoor area of the property as a PNG. Here are a few questions:

- The garage and the garage extension have internal downpipes for drainage. If I lay pipes underground in advance, how can they be connected when moving the garage? Or is it better to merge the downpipes internally (inside the garage) and then lead them outside during the garage construction?

- The existing building has its own downpipe, as does each roof area of the house. I will combine the two house roof surfaces with a T-piece. Is it typical to also combine the garage drainage and that of the existing building, and then only go into the cistern?

- I am also not sure about the cistern size and how large we should choose it. When I enter the data into online calculators, it always comes to about 2500 liters. My excavator proposed 5000 liters. The cistern should, if possible, go into the corner between the garage and the existing building. This rather speaks for a somewhat smaller cistern, as the corner back there is only 3.5 x 3 meters large. Moreover, the foundation for the heat pump still needs to go back there. It could get tight. What do you think?

- Extraction: My excavator suggested leading a suction hose into the house interior and placing the pump there. Actually, I was thinking more of a submersible pump and not going into the house at all, but rather leading a supply line directly from the cistern to the extraction points. In your opinion, which is the better option? I have too few pros and cons to make a decision. How is the submersible pump supplied with power?

- I would like the extraction points of the cistern to be south-west along the long path (this is my private path - we have built in the second row) and another one east at the house. How do you cleverly run the pipes from the cistern there? Or is the path too far for a pump?

- I would also like to only switch the pump on when water is being extracted. Is a submersible pump capable of that?

Thanks in advance for your help.

There are already many topics on this.
- direct everything possible into the cistern, including the terrace etc. (also saves fees on sealed surfaces)
- size the cistern larger (heavy rain can be used and buffering is possible), I would suggest 10,000l
- install a well pump (e.g., Tipp AJ 4 Plus 100/57 AUT), control and pressure switch already integrated, only needs electricity..
- then run away from the pump with PE-HD pipe (DN 32). Whether to a water tap, floor socket, or directly valves for automatic irrigation.

Take a look at Graf Carat XL. Even the 10,000l tank fits. Please don’t buy the sets. My suggested pump is more suitable for irrigation (pressure and flow rate).
Lawn needs about 15l/m2/week. That means 4,125l per week for you. So with 10,000l you can bridge just over two weeks of dryness. You still have to water the rest of the garden.
2,500l or 5,000l won’t bring you much.

We have 1,000m2 of lawn and a 76,000-liter cistern. That is enough for our demanding lawn (20l/m2/week) and the rest of the garden only with refilling from the well;)