Build for the environment, build for sustainability, build for your future.

Wednesday, March 18, 2009

Harvesting Rainwater from the Sky: All About Rooftop Rainwater Collection


Water is a scarce commodity. We are slowly depleting our underground aquifers, and global warming is affecting the surface bodies of water that we use for our water supplies. As it becomes more scarce, the importance of saving water is becoming ever more essential to the earth’s survival.  While there are many ways we can save our water, there is a way to increase our water supply for free—by collecting rainwater from roofs and using it for some of our household needs…

Collecting rainwater from roofs, called roof top water harvesting, is hardly a new concept born of the “green” building revolution. Going back a hundred years in the US, it was quite common to collect water from roof top gutters into cisterns or even water barrels for future use. In addition, people in third world countries with infrequent domestic water supplies will typically collect rainwater in an effort to maintain a supply of water for their household necessities. As we have become more modern, we have left behind the water collecting that was once quite common.

The benefits of water harvesting include:

• Saving money by lowering water bill
• Reducing your dependence on municipally-supplied water
• Helping to diminish local flooding and erosion
• Protecting appliances from the corrosive effects of hard water
• Reducing flow to storm water drains
• Conserving groundwater

How much water can you get by collecting rainwater from your roof? The GeoPathfinder website ( gives us a math-phobic-friendly solution:  “You can simplify the math by figuring that 1.6 square feet of flat roof will yield 1 gallon. To convert your roof’s sloped area to flat square footage, just look at how much ground area it actually covers. Then just divide that area by 1.6.” Fortunately, any amount of water saved is helping the environment and lowering your water bill.

The rainwater you collect from your roof can be used for a variety of purposes. Most simply, you can use it for watering your garden or lawn, or to wash your car. In most areas, local governments do not require permits for this type of water harvesting because the water is being used for non-potable purposes and the collection system is on a small scale. However, with a little more planning, physical labor, and paperwork, you can use the water for flushing your toilet or doing laundry. Because rain water can possibly contain contaminants such as lead (from metals in the roof), E. coli, animal droppings, and debris, you must first purify any rooftop rain water you plan on using for drinking, bathing, and using in the kitchen. 

If you are interested in collecting rainwater, you can start easily and without much difficulty. Granted, there are sophisticated systems that are highly efficient and make using collected rain water very easy, but you don’t have to use them in order to start reducing your water footprint and help save a precious resource. Basically, you can start collecting rainwater with just a plastic trashcan (covered with an insect screen) underneath the gutter spout! Even just a couple of 30 to 50 gallon tanks can definitely help out the environment and get you started down the road to conservation. Of course, this simple method will enable you to use the water for your garden and not provide clean, purified water for drinking or other situations where sanitation is required.

Once you start collecting rainwater and start seeing the real water savings that are possible, you might find it even more economical and environmentally friendly to add a water tank to collect and store the rainwater. In this way, you’ll provide it directly to typical household needs such as flushing the toilet and washing the clothes. This will allow you to bypass domestic water supplies whenever possible for these particular household uses. In many areas of the U.S., it’s possible to supply 100% of your washing machine and toilet flushing just from collected rainwater.

Builders with foresight are even beginning to include rainwater collection systems in their building plans as a way of saving water and helping the environment. They understand that the savings can be substantial for homeowners and that many buyers today are demanding “green” alternatives to wasting environmental resources. Undoubtedly, the future will bring even more focus on using existing supplies of water more efficiently—and that means collecting rainwater from roofs to use for household needs. As more people collect rainwater, the savings will be tremendous, both economically and environmentally.

Posted by casey on 03/18 at 10:21 PM
BuildingRenewable EnergyWaterEveryday LifeOutdoor StructuresRoofing


Register as a new member to leave a comment.