Rainwater cistern - Installation questions

I now also need the help of the [Hausbau Forum]!

We are planning to use rainwater in our new build, ideally for the toilets, washing machine, and garden irrigation. Unfortunately, we have a tricky hillside property and also a very shallow rainwater sewer connection (about 1.10m below street level). A 6000l concrete cistern is planned. The domestic water system is to be positioned in the utility room on the ground floor.

- Does the suction line to the domestic water system (Wilo) have to have a continuous upward slope?
- How deep do the suction line and inlet need to be buried? From what depth is the frost-free zone?
- What minimum gradient must the (emergency) overflow of the cistern to the rainwater sewer have?
- MUST the overflow definitely go into the rainwater sewer? ... Our wastewater connection is actually lower.
- How can a backflow into the house be prevented when the rainwater sewer is full? Only with a pressure seal (Doyma?)

Thank you very much in advance for your answers and help!

Greetings from the Rhineland

Hello,

We are planning rainwater use in our new building, ideally for the toilets, washing machine and garden irrigation.

Based on the feedback from our building owners, you should reconsider the topic of "rainwater use" for operating the washing machine; everyone unanimously speaks of premature graying of the laundry and, besides spending a lot of money on the system itself, has invested further resources to stop this process. Whether operating the toilets afterwards - measured against the costs - is worth the effort is something you have to assess yourself; for garden irrigation there are definitely more cost-effective systems.

For the system itself, you will probably need to have a hydrogeological report prepared - about €600.00 - from which you can then see all the parameters for construction.

Kind regards