Rainwater Harvesting: A Timeless Solution for Water Scarcity and Sustainable Living

Rainwater Harvesting: A Timeless Solution for Water Scarcity and Sustainable Living

Rainwater Harvesting: A Timeless Solution for Water Scarcity and Sustainable Living

Rainwater harvesting has been a standard of practice and use for much of the arid and semiarid regions of the Earth. In areas with low or infrequent rainfall, there is not typically enough water stored in surface depressions, the landscape, or the groundwater to meet human demands for water for consumption or irrigation. This approach to managing water dates back to the Neolithic Age (New Stone Age) , i.e., the last century of the Stone Age or up to 9000 BCE (Gregorian calendar – Before the Common Era) The early cisterns were typically associated with openings/depressions in the local bedrock and the cisterns were used for storing rainwater/surface water for irrigation and drinking purposes.

Cisterns today are typically a watertight tank that collects and stores water for later use and are typically made of reinforced concrete, cinder block, precast concrete, fiberglass, NSF 61 approved material, and even steel. If the source of the water is from a roof, the gutters and downspouts usually funnel rainwater into your cistern, and you can use that water as a supplemental supply, an emergency supply, a water source for fire suppression, or for landscape irrigation. Cisterns have also been used to store recycled gray water (mostly wash water from sinks and laundries) in homes, water that is later used for flushing toilets or irrigating the landscape. Typically, cisterns are more common in older homes that did not have a well or spring water source or when there was no local community or public water system, but cisterns are becoming more popular. The primary reason for the increased interest in cisterns is a combination of new interest in rainwater harvesting, an attempt to reduce water usage for landscape irrigation, to deal with the cumulative effects of uncontrolled stormwater runoff, “climate change”, and to avoid the increasing cost of potable water.

The recent interest in rain water harvesting can be rooted in trying to make development more climate-resistant and less vulnerable to seasonal and long-term changes in precipitation, but also to off-set the increasing cost of domestic and irrigation water. Rainwater harvesting can provide a source of water for a combination of uses that may include irrigation water, “third pipe water (flushing toilets), and drinking water. Rainwater can also be integrated into a gray water recycling system to attempt to bring the user's water footprint to something approaching zero. The simple approach might be a basic rain barrel harvesting and storage system. The Rain Barrel Project is a River Network project that helps to host rain barrel workshops in the USA and Canada. In our local area, the project has worked with the Keystone Clean Water Team and the Carbon County Conservation District to host Rain Barrel Workshops.

Question: How much rainwater runoff does my roof create?

Example: (Northeastern Pennsylvania)

Area (A) with a 1000 ft2 roof
Typically Rainfall (R) Event of 1 inch per event
40 events per year
Collection Efficiency ( E) – 80 % (For 20% permitted to runoff)


= Area * Rainfall * 0.62 (conversion factor) * Efficiency
= A * R * 0.62* E = 1000 * 1 * 0.62 * 0.80 = 496 gallons per 1” rainfall event
With 40 events per year, this would be 19,940 gallons

Assuming a typical single family home uses 250 gallons of water per day, this would be enough water to sustain a single-family home for up to 80 days – Nearly 3 months.

Note that this is a greatly simplified example. While the annual rainfall equivalent in NE Pennsylvania is approaching 40”/year (global warming), there are many more than 40 rainfall events per year, usually at considerably less than 1” per event. There could be a significant loss of potential rainfall capture from a roof due to evaporation of the water from the roof. Another complication is that not all of that precipitation comes down as rain, especially in the winter. The capture efficiency of snowmelt from the roof may not be the same as that of rain water. That 80% capture efficiency used above is very much a very rough estimate. The point still stands, however, that rainfall harvesting from a roof can make up a significant portion of the annual water consumption of a home.

Educational Information or Training

Do It Yourself (DIY)_Rainwater Harvesting “DIY: System Design, Installation, Water Purification, Storage, and Sustainable Usage (Sustainable Living and Gardening “ (Paperback) – April 10, 2024

Rainwater Harvesting Made Easy “A Beginner's Guide to Build and Maintain Your Own Sustainable Clean Water System for Your Urban Home, Rural Farm, or Homestead” (Paperback) – November 2, 2022

Drinking Water Quality - Water Treatment Technology (1 hour)

Drinking Water Quality - Monitoring & Security (1 hour)

Introduction to Sustainable Roof Technologies (2 hours)

Green Urban Design (2 hours)

Components of a Rainwater Harvest System

The major components of a rainwater system are the collection system, storage system, filtration and purification system, pumping and recirculation, and control/ monitoring systems.

Collection system

The roof surface and gutters capture the rainwater which is then diverted to a series of inlet filters or pre-filters that help to remove large inorganic and organic debris. The first flush of rain onto a roof (or highway) tends to pick up contaminants from the roof materials (especially from asphalt shingles) and dry fall (like dust). A First Flush diverter prevents this first flush from being collected which, although lowering the collection efficiency, improves the overall quality of the collected water.

Rainy® Rain Water Diverter (auto cleaning)

Rain Barrel Diverter (Oatey) 2" * 3" Residential Downspouts

Rain Barrel Diverter with Built-in Filter

Storage Tank

Storage tanks are composed of food-grade polyester resin material approved by the U.S. Food and Drug Administration (FDA) and/or NSF approved materials w They are green/dark blue/black in color which helps to reduce light transmission and algal/ bacterial growth. The other concern with color is that in some areas, if the storage cooler is too dark, the water may become heated to a point where pasteurization may occur and the water may need to be cooled prior to use. The storage tank needs both an overflow release and a cleanout port. The tank needs to be properly sized based on a combination of catchment area, regional rainfall patterns, design purpose (supplementary source of water or emergency need), and anticipated period of need. Also, do not forget the tank inlet screens.

Polyethylene tanks are widely used because they are relatively light, inexpensive, non-corrosive, and come in a variety of shapes, sizes, and configurations. In addition, these tanks are suitable for above ground, partial in-ground, inside, and below grade storage. The primary problems with these tanks is they can degrade due to exposure to UV light, a tank that is not opaque may facilitate algal growth, and in some cases, a system may require multiple tanks.

For fiberglass tanks a primary advantage is that the tanks are rigid and durable, lighter in weight, and easy to repair. However, the rigidity of the tank is a limitation because it makes the tank vulnerable to vandalism and damage and the tank may not be suitable for complete burial. Another problem with fiberglass tanks is that without an extra coating to make the tank opaque to UV light, the environment in the tank may be susceptible to algal growth.

Metal tanks may be suitable if the metal is stainless steel. These tanks are very sturdy, durable, and can handle a wide range of environmental conditions. The tanks will likely require a sturdy foundation and we commonly use these tanks in spring water harvesting projects. The primary disadvantage for this approach is cost, weight, potential for corrosion, and the need for specialized maintenance.

The storage structure could be a combination of shallow dry wells that are used to help support groundwater recharge of the water and storage in the local or regional groundwater aquifer. This way the water that would normally immediately run off is recharged into the shallow soil or upper bedrock and which then can percolate and recharge the regional aquifer and be filtered by the natural environment. We recommended a similar approach for a project in India, but in that case, we directed the roof runoff to covered sand infiltration chambers that was then directed to a series of dry wells that were within the recharge area for the regional groundwater wells.

Rain Barrel (50 gallons)

Rain Barrel Conversion Kit

Rain Barrel Connection Kit, Rainwater Diverter Kit, Rainwater Collector, Outdoor Rainwater Pipe, Rainwater Filters Water Collection System Catch RainWater (50 cm)

Treatment Concept

Treatment system: This system must use a multiple barrier approach that will need to include filtration, a disinfection system, possibly neutralization, and ion exchange to ensure that the water is potentially potable if this is the goal and objective. The first step is to get samples of your rainwater tested. While working on my undergraduate degree, my work study program included water quality testing of dry fall and rainfall. As part of this experience, I learned dry fall includes particles of soot and a combination of inert and reactive inorganic and organic material which, when mixed with water, created a weak acidic solution that could have detectable levels of radioactive material. In the 1970s in NE Pennsylvania,the rainwater following a thunderstorm could have a pH as low as 3 (acid rain due to the burning of coal). The normal pH of “uncontaminated” rainwater is about 5 to 5.5 due to dissolved carbon dioxide gas.

Water Testing Kits Rainwater

Tap Score: Essential Rain Water Test The testing includes heavy metals, minerals, general chemistry, silica, coliform, and E. coli. (Bacteria)

Tap Score: EAdvanced Rainwater TestThe testing includes heavy metals, minerals, general chemistry, silica, coliform and E. coli., trihalomethanes, and volatile organic compounds (VOCs).

Water Treatment

The U.S. Water System company does not sell rainwater collection systems, tubing, tanks, piping and supplies: rather they provide what they are really good at and that is rainwater harvesting water treatment systems.

US Water System Diagram

Blog Article: Rainwater Harvesting When There Is No Other Choice

The Crystal Quest Off-Grid Crystal Quest Off-Grid, Portable R.O. Water System combines both Reverse Osmosis and filtration to purify water from a variety of water sources such as lakes, streams, rivers, etc. Great companion for off-grid living, boating, camping, emergency prepping, and disaster-hit areas. The Crystal Quest Off-Grid Reverse Osmosis Water System is a portable, compact, mobile, and solar/battery-powered all-in-one water treatment system that utilizes a Reverse Osmosis membrane with sediment and carbon block filters to clear contaminants out of the water. There is also a Crystal Quest Whole-house RO System, to which you should add a UV disinfection system and a remineralizer.

Pumping System

A pump or pumping system operates the treatment system, the distribution system, and the recirculation components of the system. Backflow preventer devices ensure that under negative pressure water cannot flow backwards through the system into the make-up water system.


A Control system monitors water, water use, and operations for the distribution and filtration system.

A Flow meter (with data logger) measures water production and usage.

Power supply: Systems may use either conventional power sources or, to improve off-grid capabilities, alternative sources such as stand-alone or grid-tied solar systems.

A Water level indicator monitors the water level in the storage tank.

The system will need a basic Operation and Maintenance Manual and monitoring equipment to field-check water quality of the untreated and treated water.

The Pacific Northwest National Laboratory (PNNL) in collaboration with the Federal Energy Management Program (FEMP) developed an online GIS-based Rainwater Harvesting Tool to help federal agencies strategically prioritize commercial rainwater harvesting projects by providing rainwater harvesting potentials across the United States.

Other articles

Water Conservation | Tips on How to Save Water Inside and Outside the Home Stormwater Management for Homeowners

Educational PDFS

How to Make a Plan: “Homeowners Guide to Stormwater" for Pennsylvania

Pennsylvania Homeowners Guide to Stormwater

Rain Barrel Installation Instructions (Rutgers Cooperative Extension)

Build Your Own Rain Barrel (Chesapeake Bay Foundation)

Roof Top ReDirection

Using Grass Swales

Rainwater Harvesting: Guidance for Homeowners (North Carolina Cooperative Extension)

Rainwater Harvesting 101: Identifying a Well-Designed Rainwater Harvesting System

American Rainwater Catchment Systems Association (ARCSA) - Rainwater Harvesting 101: Maintaining a Rainwater Harvesting System

Choosing a Pump for Rainwater Harvesting

Rainwater Harvesting: Guidance for Homeowners

Texas Rainwater Harvesting Manual

Another type of “rainwater” harvesting is the atmospheric water generators. An atmospheric water generator extracts water from the humidity in the atmosphere and then passes that water through a water treatment system to make it potable. So, basically it is a dehumidifier connected to a water treatment system.

Atmospheric Water Generation Research (archived)
“AWG generators range from home-based units that can produce 1 to 20 liters of water per day to commercial-scale units capable of 1,000 to over 10,000 liters per day. Water production rates are highly dependent upon the air temperature and the amount of water vapor (i.e., humidity) in the air. The most commonly used AWG systems employ condenser and cooling coil technology to pull moisture from the air in the same way a household dehumidifier does. Although significant quantities of energy can be required to operate these condenser and fan systems, recent technological advancements have substantially improved the energy-water ratio—increasing the feasibility of using these systems to help augment the Nation’s drinking water resources.”