Rainwater harvesting is one of the best ways of conserving water in an era where every drop counts. But, while consumers, in general, are aware of the necessity to conserve energy, a much smaller percentage is conscious of the need to conserve water.
The good news is that conserving water by harvesting rainwater is in fact very easy and not only will you be taking steps to help save the planet, you will also save yourself a whole lot of money by cutting down on utility charges. You will also find it effortless to meet regulatory needs of reducing and controlling storm-water runoff volumes and the pollution loads so often associated with it.
Here is some fairly basic information that will help you get started, but you may prefer to consult with an engineering firm that specializes in plumbing, or a mechanical, electrical, and plumbing (MEP) engineering firm in Chicago, New York, Toronto, or close to wherever you live.
Rainwater Harvesting Systems
There are two main types of rainwater harvesting systems:
- Passive systems like rain barrels and other above-ground containers that usually involve smaller 50- to 100-gallon volumes from rooftop runoff.
- Active systems that are able to harvest larger 1,000- to 100,000-gallon volumes from roofs as well as other surfaces including terraces and walkways.
While various U.S. states have different rules, requirements, and regulations relating to the harvesting of rainwater and storage of the water collected, most consider water collected in rain barrels to be non-potable and only suitable for outdoor use. This includes garden use, for watering plants
Barrels should be screened so that insects and disease-carrying creatures don’t breed in and around them.
Typically, passive systems have an overflow that releases excess water into the nearest storm-water drain or simply allows it to flow out of the barrel. Most have a spigot through which the water may be extracted.
When choosing a barrel or cistern for a passive rainwater harvesting system, avoid light or opaque colors. If water is exposed to sunlight, it will tend to act as a catalyst for algae growth, and you don’t want that to happen.
Generally, passive systems require very little maintenance and they cost next to nothing to run. It is, though, a good idea to clean them annually, and it’s essential to keep the catchment area clear of debris. Of course, gutters and downspouts that direct water into barrels must also be kept clean.
Active systems are designed, usually by an engineer, to suit specific locations and water-volume requirements. They incorporate an appropriate distribution system as well as suitable water treatment facilities. Integrated systems supply water for indoor and outdoor use and provide potable water.
Most active rainwater harvesting systems are fitted with a pump or pumps as well as electronic water-level sensors and other control mechanisms. They are often designed so that municipal water is available as a back-up when there is no rainwater available in the tank. However, many states have regulations that restrict the use of mechanical backflow apparatus and require the use of smaller tanks for municipal water supply. In this event, water cannot be fed directly into the plumbing system of the building.
Cisterns and other containers for active rainwater harvesting systems are manufactured from various different materials including plastic, metal, wood, and concrete. Several states, including North Carolina, Virginia, Georgia, and Texas, have guidance manuals for suitable treatment systems. Several cities, including Los Angeles, Portland, Tucson, and San Francisco, have policy documents that cover local requirements including treatment of the water. In states where there are no regulations and no available guidelines for harvesting rainwater, these documents can be very useful.
Active systems are considerably more efficient in terms of both storage volumes and delivery. Maintenance is similar to that required for passive systems, but, because there are more components, additional upkeep will be required for filters and other elements.
How Rainwater is Used
An enormous amount of water used is not required to be potable (or fit for drinking). Because of this, it makes absolute sense to use harvested rainwater rather than treated drinking water for these needs.
The American Water Works Association (AWWA) and various other bodies have estimated the end uses of water not required for drinking (ie non-potable water) in various sectors. Figures published by the United States Environmental Protection Agency (EPA) in a Rainwater Harvesting review several years ago, show that the greatest use of non-potable water was for landscaping and other outdoor use, followed by toilets and other restroom uses, laundries, kitchens, and in commercial buildings, cooling and process water. More specifically percentages for residential(shown first) and commercialuse were:
- Landscaping/outdoor – 59% & 35%
- Toilets – 11% & 12%
- Other restroom uses including cleaning – 11% & 4%
- Laundry – 9% & 2%
- Other (not specified) – 7% & 9%
- Kitchen – 4% & 6%
- Cooling – 0% &15%
- Process water – 0% & 17%
The AWWAhas also estimated water usage for various commercial and industrial operations.
In all instances, climatic and regional factors impacted on the results. For example, in Denver, Colorado in the mid-west, schools use about 29% of their non-potable water on landscape irrigation, while in Phoenix, Arizona, in the southwest, they use 54%, which is nearly double the quantity.
In line with this, when a rainwater harvesting system is designed by a company that provides plumbing engineering services in Chicago, San Francisco, Los Angeles, or any other city or town, it is essential that it will meet water demands. This will depend on the needs of those living or working in the house or building but will be largely determined by rainfall patterns. If typical rainfall figures are insufficient, then the system will need to be designed accordingly. In reality, it is challenging to try and match supply and demand.
At very least, why not get a rain barrel and implement a passive system? You can always expand the system later.