if the ground (infiltration coefficient) and the terrain allow it, I would connect a few underground infiltration blocks to the overflow of the cistern for a few hundred euros. I would not want to put up with forced irrigation in winter with possible freezing and even freezing of the pipes
It means that the surface water from unvegetated roofs should be collected, and that the cisterns used for this purpose should not only retain the water (i.e., delay its discharge into the sewer system) but also that the water should be consumed from them (i.e., that none of it needs to be discharged). For this purpose, one's service water demand should be covered with this water. "Service water" is a term for water intended for use without special quality requirements. In this sense, the term distinguishes it from "drinking water" (intended for consumption, requiring assured quality). Consumption should therefore not have to be accomplished by using the water also for drinking water purposes. The wording has legal reasons, nothing more. Practically, this only means: only those who can make use of the corresponding amount of precipitation running off such roofs themselves should leave roofs unvegetated."Unvegetated roof surfaces must be connected to cisterns. The water is to be used as service water."