Georg and Beate Tolle's farm in Calden-Fürstenwald, in Hesse, is run organically. The construction of a 20 m³ underground cistern in 1998 when they had to rebuild the barn was a natural step the couple took. Rainwater is collected here from the 800 m² roof surface. A DN 150 downpipe for each half of the roof leads down to the rainwater tank. And a WFF 150 vortex fine filter, by WISY AG, is fitted in each downpipe. Dirt is reliably filtered off from the useable water, such that cleaning of the cistern is not necessary. The rainwater is used for cattle troughs, to clean animals and tools and also to flush the toilet.
The state of Hesse has contributed to the costs of the rainwater harvesting system, which amounted to almost EUR 13,000, from ground-water payments. The rainwater from the building remains completely on the property. What is not used, runs off into an underground seepaway system.