Rainwater Harvesting

Introduction                                                                                                                   Rainwater harvesting is an ancient technique enjoying a revival in popularity due to the inherent quality of rainwater and interest in reducing consumption of treated water.

Rainwater is valued for its purity and softness.

It has a nearly neutral pH, and is free from disinfection by-products, salts, minerals, and other natural and man-made contaminants.

Plants thrive under irrigation with stored rainwater.

Appliances last longer when free from the corrosive or scale effects of hard water.

Users with potable systems prefer the superior taste and cleansing properties of rainwater.

The water is free; the only cost is for collection and use.

The end use of harvested water is located close to the source, eliminating the need for complex and costly distribution systems.

Rainwater provides a water source when groundwater is unacceptable or unavailable, or it can augment limited groundwater supplies.

The zero hardness of rainwater helps prevent scale on appliances, extending their use; rainwater eliminates the need for a water softener and the salts added during the softening process. Rainwater is sodium-free, important for persons on low-sodium diets.

Ladies say that when they wash their hair with rainwater it is allways much softer.

Rainwater is superior for landscape irrigation as it is natural with no added chemicals.

Rainwater harvesting reduces flow to storm water drains and also reduces non-point source pollution.

Rainwater harvesting helps utilities reduce the summer demand peak and delays expansion of existing water treatment plants.

Rainwater harvesting reduces consumers’ utility bills, recently just increased by a further 12%.

When assessing the health risks of drinking rainwater, consider the path taken by the raindrop through a watershed into a reservoir, through public drinking water treatment and distribution systems to the end user.  

Being the universal solvent, water absorbs contaminants and minerals on its travels to the reservoir. While in residence in the reservoir, the water can come in contact with all kinds of foreign materials such as oil, animal wastes, chemical and pharmaceutical wastes, organic compounds, industrial outflows, and trash.

It is the job of the water treatment plant to remove harmful contaminants and to kill pathogens. Unfortunately, when chlorine is used for disinfection, it also degrades into disinfection by-products, notably trihalomethanes,(Google trihalomethanes) which may pose health risks.

In contrast, the raindrop harvested on site will travel down a roof via a gutter to storage tanks. Before it can be used for drinking, it will be treated by a relatively simple process with equipment that occupies about 1 cubic meters of space.

Rainwater harvesting can reduce the volume of storm water, thereby lessening the impact on erosion and decreasing the load on storm sewers.

Decreasing storm water volume also helps keep potential storm water pollutants, such as pesticides, fertilizers, and petroleum products, out of rivers and groundwater.

But along with the independence of rainwater harvesting systems comes the inherent responsibility of operation and maintenance.

For all systems, this responsibility includes purging the first flush system, regularly cleaning roof washers and tanks, maintaining pumps, and filtering water.

For potable systems, responsibilities include all of the above, and the owner must replace cartridge filters and maintain disinfection equipment on schedule, arrange to have water tested, and monitor tank levels.

Rainwater used for drinking should be tested, at a minimum, for pathogens.

Rainwater harvesting, in its essence, is the collection, conveyance, and storage of rainwater. The scope, method, technologies, system complexity, purpose, and end uses vary from rain tanks for garden irrigation in urban areas, to large-scale collection of rainwater for all domestic uses.

More are being installed by the urban home gardener seeking healthier plants, the weekend cabin owner, and the homeowner intent upon the “green” building practices – all seeking a sustainable, high-quality water source.

Rainwater harvesting is also recognized as an important water conserving measure, and is best implemented in conjunction with other efficiency measures in and outside of the home.

Rainwater harvesting is practical only when the volume and frequency of rainfall and size of the catchment surface can generate sufficient water for the intended purpose.

With a very large catchment surface, such as that of big commercial building, the volume rainwater, when captured and stored, can cost-effectively serve several end uses, such  as landscape Irrigation and toilet flushing.