Introduction for Rainwater harvesting

Harvesting Rainwater for saving drinking water has gained enormously in significance as a modern water saving sanitary technique. This can be used for private and public buildings as well as for many industrial areas. Beyond that rainwater harvesting plays an important …….. for the rainwater (stormwater) management of housing estates. Due to the storage (retention) and the usage of rainwater the water flowing off housing estates in both reduced and delayed.

Rainwater harvesting – a system for conserving resources

Daily in Germany a huge amount of ground water is transported. It is used by households, communal institutions, as well as trade and industry. The used rainwater is drained as quick as possible via the sewer info into the purification plant.
Due to the sealing of areas with buildings or the paving of traffic areas and places the possibility is taken away from nature to generate more groundwater from precipitation in the required amount. So locally it can result in drastic lowering of the ground water level because in housing estates the rain can't be used for replenishing new ground water. Also, intense or long periods rain draining to sewers produces floods in rivers.
The first step for responsible handling of the basic food stuff “Water” should be water saving behavior and using water saving utensils. Due to the rising demand for water saving utensils through the consumer the industry developed better and better technical solutions. For example the average water usage of washing machines in 1970 was 140 litres and by 1992 it was reduced down to 50-60 litres.
But not only due to the usage of water saving tools can water consumption can be reduced.

Other small changes can show a big effect:

• The consumption can be halved from 8-12 litres in old toilet cisterns per flush down to 4-6 litres in modern toilet cisterns

• Also water saving pressure flush with 3- and 6- litres push buttons are now commercially available

• Leaking of water taps should be watched, dropping water taps can waste 5.000 litres water in a year

• Personal behavior helps saving water. During teeth's cleaning you must not leave the tap on or having a shower instead having a bath. It saves a third of the normally used water.

• Also water can be saved in the garden. Only water your plants early in the morning or in the nights.

Further steps for responsible handling of water could be rainwater harvesting

One possibility is the decentralized Rainwater soak away. Here the flowing of rainwater is carried up to the ground (as near as possible to the outlet on the down pipe). So it can be used for ground water replenishment.
Another opportunity is to replace drinking water in a household where no drinking water quality is required.
The idea of collecting rainwater in reservoirs an to use it in dry periods is as old as the human culture. Very often you can find something about tanks in the Old Testament. Until today in countries, poor of rainwater tanks are created to have a buffer for the periods between rain- and dry- periods. Also you can very often find rainwater tanks on islands to cover the fresh water demand.
More and more in Germany consumers develop an ecological thinking. Also with the growing water costs the realization grows that the drinking water quality is not required for everything.
The rainwater butt for garden use is standard again after it was proscribed for a long time.

Replaced of drinking water with rainwater is possible when drinking water quality is not required. Rainwater is great for toilet cisterns, where it is only used for rinsing the toilet and transporting away faeces. Another good possibility for using rainwater is washing clothes. Rainwater is very soft. The washing machine has significantly less problems with lime sedimentation and the usage of washing powder is reduced.
Meanwhile the installation of rainwater plants is supported by some communities, direct or indirect, sometimes even with financial help, as an arrangement for active ground water protection.

The installation of a rainwater harvesting plant is as follows:

The flow from the roof is led through a filter into a tank. Different Tanks allow a filter installation inside the tank as well as outside. Due to the calmed inlet of rainwater the finest dirt is able to settle on the bottom of the tan which results in another water quality improvement. To control the overflow of the tank there must be a connection to the sewer or, better, to a soak away.
The water collected in the tank is abstracted by a suction pump from above sedimentation to the points of use in the home. Due to an automatic water level sensor, and a topping up system the continues supply of water from the tank is assured, by controlled drinking water top up only if the tank is empty. The drinking water topping up happens as required. Only so much potable water is used for topping up as it needed.
The installation of a rainwater plant has to correspond with the regulatory situation and instructions. That means the rainwater plant has to be registered with the local water supply company and it is recommended that an expert carries out the installation because only the expert knows all the exact laws and rules.
For the rainwater usage in the house from different companies specific designed plants are offered. The cost for a rainwater plant for a four person household is about 4000 Euro.
If you look at the average water usage and the possible saving potential from responsible handling of water and rainwater harvesting you will save significantly due to reduced drinking water demand. One person needs daily in average 128 litres of water. Due to the presented water saving arrangements the usage can be reduced down to 100 litres. Due to using rainwater in a household another 30 litres can be saved.

Dietmar Sperfeld