Georgia Water/Best Practices/Conservation/Rainwater harvesting

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This book describes the types of common rainwater harvesters which are usable in practice and which can be built DIY. Also, the book provides some basic how-to content on how the harvesters can be built in practice. Rainwater harvesters are devices used to gather, or accumulate and store rainwater.

Systems

Schematic showing how rainwater can be obtained from hillsides

There are many types of systems to harvest rainwater. Notable systems are systems for runoff rainwater (e.g. hillside run-off) and rooftop rainwater harvesting systems. The type used depends greatly on the purpose (domestic or industrial use) and to some extent also on economics and physical and human considerations. Generally speaking, rooftop rainwater systems are most used as they are most economical (if there is more than 254mm of precipitation a year) To determine the amount of precipitation falling in your area, refer to this map.

Domestic rooftop rainwater systems

A domestic rooftop rainwater harvesting system

The regular set-up of a pressurized rooftop rainwater harvester

System types

At the moment, 2 types of systems are generally used. These include DIY and commercial systems. Both of these systems are known under the term water harvesters and require only a limited amount of knowledge to set up (if basic systems are used). In both cases, the system consists of a storage tank to store the water and piping (to guide the water in). Additionally, extra pressuring equipment as pressure vessels, inline pump controllers or pressure sensitive pumps may also be required. Finally, water purifying equipment such as water-purifying plants, ultraviolet light or distillation equipment are sometimes added to purify the collected water, depending on local conditions.

A water collection system that processes water from sinks or showers is called a Greywater treatment system. Greywater systems are usually preferred over regular water harvesters for the increased volume and regularity of water.

Depending on local circumstances, a gravity-fed system may provide enough pressure for water distribution. In the latter case, no pumps/pressure vessels are thus required to have a pressured system. In practice, gravity-controlled systems are usually created by placing the water harvester on an elevation (e.g. rooftops).

DIY domestic systems

As water conservation is becoming more and more popular, more people have begun to make their own homebrew installation. These systems range from traditional technologies like rain barrels to more complex greywater systems. Through the Internet, plans and accurate construction information have become available. Depending on the degree of personal skill and preference, a more basic (regular water tank and piping) -or more advanced (e.g. pressured systems with water treatment, etc.) system is chosen.

Commercial domestic systems

Commercial systems are also made. They are offered by a variety of companies ... Commercial rain harvesters can be obtained in both pressurized as gravity-fed systems . Greywater treatment systems are sold by companies as Water Works UK, Nubian Water Systems, BRAC Systems, ... Again, they are available in pressurised as gravity-fed systems.

System's operation

A mechanism can be used to send the initial water flow to waste, usually the first few liters. These are commonly known as 'first-flush' diverters, and are used to increase the chance that the large-particle residue that might accumulate on your collection surface is washed away from (and not into) your storage tank. Such a system also compensates for the fact that the initial minutes of a rainfall can include airborne pollutants being washed from the sky, and likewise minimizes contamination of your captured supply. Simple but regular inspection and maintenance of such a device is usually necessary.

Not all catchment systems use such a feature. For example, rainwater in rural areas of Australia is traditionally used without such a system, and without treatment, but this may be unwise as it can contaminants that can cause diseases in different environments.

Industrial systems

Rainwater may also be used for groundwater recharge, where the runoff on the ground is collected and allowed to be absorbed, adding to the groundwater. In US, rooftop rainwater is collected and stored in sump. In India this includes Bawdis and johads, or ponds which collect the run-off from small streams in wide area.

In India, reservoirs called tankas were used to store water; typically they were shallow with mud walls. Ancient tankas still exist in some places.