In an average household, each person uses about 150 liters of domestic water daily. Only 2% of that is used for cooking. 35% of our domestic water is flushed down the toilet (without water-saving system). This means a large savings potential in water consumption. We obtain rainwater free from nature, so we should use it.

Potential savings

• With toilets with a 6-liter tank and a water-stop button, you can save significant amounts of water. 
• The installation of water-saving shower heads and kitchen faucets makes sense 
• If water is not available, compost toilet systems can be used. With proper installation, they are odor-free and hygienically harmless. 
• A vacuum toilet system enables ca. 90% water savings and significantly smaller pipe diameter. They can also be used for toilets under sewer level.

Rainwater instead of drinking water

• With new construction, you can plan a rainwater harvesting system from the start. 
• This can be located externally or internally (e.g., in the basement).
• The storage tank should be easy to clean and nonmetal (corrosion) 
• Use harvested water for flushing toilets, washing machine and lawn & garden watering.
• Instead of connecting the domestic water, connect the rain water to all toilets. 
• If the weather stays dry for long periods, then domestic water can be fed into the rainwater tank. 
• Rainwater and drinking water lines must be completely separate 
• For use in the household, rainwater must be filtered, whereby there are different filtering stages:
  • for toilets: simple filter bowl
  • for washing machine: fine filter
• In areas with hard water, the use of rainwater saves detergent.
• Keep rainwater cool and dark: bacteria grow rapidly above 15° C and with light. 
• Do not over-size the storage tank (long standing times lead to hygienic and odor problems).
• Average size: 5 - 8 m3 per household, depending on utilization and required degree of coverage. 
• Garden watering: 6 m3 per 100 m2 to be watered annually. 
• Rainwater harvest = roof area x amount of precipitation (in Austria approx. 900 liter/m2) x drainage value (for tile roofs 0.75). 
• It makes sense to have a tap for other uses (label: Not drinking water).