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Approaches for water demand management
Water saving devices and appliances

Peter Thomas
HATI - Company for craft technology and innovation, Berlin

As a plumber, my understanding of water demand management is focused on the usage of water inside buildings and on outside rainwater treatment. Since in Berlin more than 90% of the inhabitants live in residential homes with more than 20 persons, I have specialised in the water household of these buildings.

When I started with my work in the mid-seventies, most of the old residential homes in Berlin had only one tap inside the flat. Several families had to share the toilet on the main floor. In these old homes the water consumption was 50 to 70 litre per person a day.
In the same period, the water consumption in modernised homes and new flats was three times higher as in the old residential homes. Publications of the waterworks show that per person, 170 to 210 litre were consumed every day.

Core element of this integrated urban waterproject in Berlin is an aprroximately 800 m² large graywater purification plant. The plant is situated like an island within an approx. 1.000 m² large rainwater pond.

Without a vision of efficiency watermanagement, town modernisation leads to a three times higher water usage and sewage. To be able to deal with the higher water consumption, new water catchment areas and also tract of land should be applied to purify the three times more sewage.

In the former situation of West-Berlin, which was surrounded by the wall, there were neither additional restricted areas for water catchment nor were there areas for sewage plants. This situation is similar to that of most big cities in the world. In the beginning of the 80-ies, other waterworks in Germany like Hamburg, Munich and the agglomerate Frankfurt, had big problems to retrieve enough water from the water catchment areas because of dehydration.

Therefore, watermanagement needs to be an integrated part of the local governments modernisation and town-renewal strategies.

The political discussion on the field of energy (resistance against nuclear energy) late 70-ies / early 80-ies mobilised some societal groups to surge for practical solutions.

One of the consequences of the energy crisis was, that in the beginning of the 1980-ies one started to separate graywater, just to subtract the thermal energy from the graywater. The additional costs for the separate pipes, the integration of a reservoir and a heat exchanger was only financed with the saved energy costs.

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