More than 1.8 million German households and companies collect rain in concrete or plastic tanks, in order to water the garden, flush the toilet or wash their cars. About 110 million cubic meters of valuable drinking water have been saved in 2009, nationwide.

Last year at least 60 000 new rain water tanks were built in Germany – making the country the largest market in Europe. The neighbors are catching up slowly. France had around 20,000 new installations in 2009 (2010 trend - rising), the United Kingdom had 6,000 tanks (with a strong rising tendency), while Switzerland installed almost 1,000 and Austria about 2,500 units (both with a slightly increasing trend).

The figures are for one- and two-family houses. They come from a recent study by the German environmental technology company Mall (http://www.mall.info/en/company.html). For the second time since 2004, Mall had carried out wide consultations and market analysis among associations and leading companies of the rainwater harvesting industry.

The rain water industry had to face some setbacks in the last years because of the economic crisis. As a result of weaker construction activity, the number of new installations has fallen by almost 20 percent ? but their share in new buildings has risen sharply: in 2009 already 44 percent of newly built single-family homes were equipped with rain water systems.

In addition, the sales of large systems rose significantly. More and more industrial companies are investing in facilities for rain water harvesting. Recently they discovered rain water for cooling tasks in production processes.

Cities and municipalities are increasingly relying on water from the sky, too. According to the Mall study, many new development areas are built with a requirement of implementing rain water tanks in gardens or adding rain collection systems under streets, parking lots etc. The latter can, for example, help in stormwater retention during heavy rain or as water storage for the fire department.

One in three new rain water tanks is being installed in an old building. For example, the City of Falkensee in Germany's federal state of Brandenburg installed a rain water storage system in an existing school with 1,000 students. The roofs of all buildings were connected to a central underground cistern. The toilet flush is controlled automatically by the rain water control center. If the underground water storage is completely filled and it still continues to rain, the overflow is discharged into a pond. There some water evaporates, while the rest seeps away. The pond was created as a biotope-like landscape element.

"Many systems pay for themselves in eight to ten years," says Klaus W. König, Vice President of the German Association for Rain Water Harvesting and Water Utilisation (http://www.fbr.de/english0.html), "because every rain water system user saves money on drinking water fees, ultimately having to pay less sewage charges."

The European Union is turning increasingly to the topic, too. There is currently a directive being planned for the water use efficiency of buildings. According to the findings of the Commission – better use could save almost a third of the water consumption in some regions. Exactly what the directive will look like is still unclear. "It could lead to a water certificate for buildings," says Klaus W. König, "comparable to the already existing German energy efficiency certificate. It could, for example, contain the average consumption per inhabitant." As an accompanying measure, the water specialist imagines an obligation for new buildings to provide a second piping network for rain water. "That would cost almost nothing because the tubes are simply placed parallel to the drinking water network of the new houses", says König.