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Cleaner Technology Projects in Denmark 1996

Reduction of Water Consumption in Residences

This report evaluates the possibilities of reducing the water consumption in residences and what the consequences are for the existing drainage systems. This report should be considered a supplement to already existing guides concerning the reduction of water consumption in residences.

In Denmark the water supply is based on ground water which is used for drinking water without extensive purification. During recent years the increased consciousness of the necessity of reducing the water consumption, if status quo shall be preserved, has produced numerous technical initiatives for water saving measures.

This development has been furthered not only by the environmental aspects, but also by the increased excises on water and drainage.

In the industries water-saving measures have been developed and implemented as a consequence of an increasing number of water consuming processes. Within the building industry campaigns have been carried through with the objective of informing the consumers of do-it-yourself measures to reduce the water consumption.

The campaigns have primarily been aimed at changing bad user habits and proposals for purchase and installation of simple water saving devices. Proper package solutions where savings are obtained without the awareness of the consumer and where the savings – such as reduced water flow incorporated in the design of water pipes and drainage pipes – are not yet available. Instructions for the design of systems where rainwater and "grey waste water" are recycled are also not available in a general, accepted form.

Chapter 2 of this report is about water savings in a general way and describes some of the possibilities of reducing the water consumption by means of relatively simple measures.

Chapter 3 is about the possibilities of designing water pipes so that the reduced water consumption results in smaller pipe dimensions and thus reduces the consumption of pipe materials.

Chapter 4 describes in detail the subject of water saving toilets. In private dwellings the toilet accounts for the largest water consumption and furthermore the flushing water from the toilet is important for the natural purification of the drainage system.

A reduction of the amount of flushing water means that special measures must be taken when the discharge system is designed. These measures are amplified in chapters 5 and 6.

Chapter 7 gives detailed instructions on the design and execution of drainage systems that have been approved for use together with water saving toilets. Chapter 8 describes an approved renovation system with smaller pipe dimensions than traditional systems. This is done by using toilets that flush with 3.5 l of water per flush.

Chapter 9 describes, by means of figures and text, a tool for assessing the condition of old drainage pipes. This method makes it possible to decide whether there is a risk of blocking water saving devices are installed in an existing drainage system.

Author/ institution

Inge Faldager and Viggo Nielsen, Dansk Teknologisk Institut. Rørcentret

This report is subsidised by the National Council for Recycling and Cleaner Technology.

ISSN no. 0908-9195
ISBN no. 87-7810-640-0

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