Rain harvesting

By Shawn Hatley on 02/01/2008

What about rainwater harvesting?

It’s true that in order to collect rainwater, it must rain. But when it does rain, as many as 60,000 gallons of rainwater per year may fall on a 2,000-square-foot roof in the Mid-Atlantic states. Harvesting this amount from just 100 homes in a single neighborhood, we could easily conserve 6 million gallons annually. How many neighbors do you have?

Consider this: If just 15 percent of residential landscapes in the United States were irrigated with rainwater, more than 1 billion gallons of water could be conserved daily, according to the American Rainwater Catchment Systems Association.

In addition to the obvious advantages of rainwater — it’s free of charge, and it doesn’t have to be treated or transported over long distances — there are two important arguments for utilizing this resource:

1. As a supplement to drinking water resources, utilizing rainwater has the benefit of saving precious, potable water.

2. By reducing the impacts of storm-water runoff, rainwater harvesting protects water quality and limits the flooding and degradation of streams and lakes.

How do we harvest rain?

By simple definition, rainwater harvesting means collecting the rain for later use. When deciding which rain-harvesting system is right for your project, consider the following:

• Budget: If you have a specific dollar amount in mind, then your simplest task is picking the best system for your well-earned dollar. Remember, storage is the No. 1 cost for rain-harvesting systems, and most above-ground tanks are more affordable than below-ground. Systems can cost as little as a few hundred dollars, and as much as tens of thousands of dollars.

Myth No. 1: Rainwater systems are expensive! Debunked: With complete rainwater systems available in all price ranges, you can easily select a system that is right for your budget.

• Project goals: Not all projects are the same. If you are a hobbyist perhaps you want a system with small to medium storage capacity and good water pressure for outdoor gardening. Maybe you have a drainage problem and want a system big enough to prevent water from entering a basement or a neighbor’s property. Are you living in a community that prevents the use of city water for landscape irrigation? If so, choose a system large enough to maximize collection potential. If your system will be used for fire protection, aim for a higher capacity.
• Do-it-yourself or do-it-for-me? Selecting the right system is a big step, but getting it installed and operational can be a bigger step — depending on which system you choose. Not all systems require professional services, however. If you require professional installation of your rainwater system, choose a locally available contractor whom others recommend.

What is included in a complete rainwater system?

• Filtration: This is the initial step for ensuring only the highest quality water enters your storage tank. Filter water before storing water!
• Storage: The most important component of a rainwater system. When selecting a rainwater cistern/tank, ask yourself: Will I store the water above ground or below ground? What appearance do I want for my above-ground tank — wooden, steel or plastic? How much storage do I need?

Myth No. 2: Rainwater storage tanks are ugly! Debunked: Rainwater storage does not have to be unsightly or ugly. There are many attractive above-ground storage tank options to choose from. How about installing your storage below ground? It is hard to be ugly if it is out of sight! Design tip: Use black or dark-green tanks opaque to light for above-ground storage. Tanks that are not opaque allow light to grow algae in the water and cause water quality problems.

• Pump systems: Pump systems deliver rainwater to end-use applications. They can be sized to pressurize small garden hoses, supply school buildings with rainwater to flush toilets, or to irrigate ball fields.

Myth No. 3: Rainwater systems do not have pressure! Debunked: Rainwater collection systems are often offered with pump systems that can deliver 5 to 500 gallons per minute. Rainwater systems don’t have pressure if you rely on gravity, because for every one PSI (city/well water is generally 30-50 PSI) you would have to elevate your tank 2.31 feet. To get 30PSI, you’ll need to elevate your tank 69.3 feet. I hope you live in the mountains!

• Water treatment: This refers to the process of purifying rainwater to meet end-use water-quality requirements. For example, irrigation systems require sediment screen to prevent clogging of spray heads.  Projects requiring a higher level of protection use high-efficiency carbon filters and/or Ultraviolet (UV) disinfection as the ecological choice for non-chemical water purification. 

Where can I rain harvest?

Anywhere! Rainwater systems can incorporate simple rain barrels located below a single downspout to capture the rain, but can also be large tanks located below ground at a school for collecting the millions of gallons of rainwater each year. Office buildings, churches, houses, parks, zoos, schools and manufacturing facilities are all suitable locations to collect the rain. Below are a few more common applications:

• Water supply: Common challenges include low-producing wells, high irrigation demands, expensive municipal water, and/or lack of water, period. Rainwater offers a supplemental water source to existing water supplies (well, spring, city water) and can help meet more than 65 percent of daily nonpotable demands.
• Storm-water runoff / drainage control: With real-estate values skyrocketing, the costs of storm-water damage to your investments can decrease their value tremendously and increase your liability. Rainwater harvesting is a best-management practice for reducing storm-water runoff. Ideal for use in combined sewer or high flood-risk communities, rainwater cisterns capture storm-water during heavy rains, mitigating flooding of sewers and flood-susceptible areas and protecting sensitive water quality in streams, lakes and rivers. Rainwater cisterns store rooftop runoff, thereby diverting rainwater away from structures. This practice helps avoid problems associated with water seeping into basements or crawl spaces and creating wet-mold problems.
• Fire protection: Today, it is more common for neighborhoods and commercial facilities to integrate cisterns with fire-protection systems. Due to the remote location of some homes and commercial buildings in mountain regions, available water supplies for fire protection are severely limited or not present. To address this problem, rainwater cisterns are being installed for individual homes, and communities are integrating single large cisterns to protect multiple homes in case of fire. As an added benefit, some insurance providers recognize this practice and provide reduced premiums for participating projects.

With the South experiencing unprecedented drought, our communities will continue searching for ways to supplement and extend available water resources. Rainwater harvesting is one practice out of many that will help meet water-supply challenges throughout the Southeast. Easily taught and simple to implement, challenge yourself to add a rainwater-harvesting system to your home, business or school. You may be surprised how much water it will collect!