In one of our recent projects, we installed a rainwater harvesting system that captures 100% of the roofs’ runoff water. The water is captured through gutters and then routed into a 16,000 gallon tank. For this purpose we installed a “trunk line” all the way around the home’s perimeter. All the downspouts of the gutter system “feed” into this trunk line which is connected to the tank. The water is pushed into the tank by gravity and then pumped out when needed. One important aspect of the system is the pre-filtering system, on this project we used a product called “Gutter Foam”. You can find details about their product at http://gutterfoam.com. You can see in the picture that the foam piece is wedged in the gutter and prevents any debris from entering the system.

The tank is a galvalume tank with interior liner set on a sand & gravel base. It has a backup line from the city water meter in case the water level ever drops too low. At this point the backup kicks in and fills the tank to minimum level with city water. Water is pumped out of the tank with a Grundfos pump and filtered through a UV-filtration system. That way the water will not carry and “foul” odor, especially if it is used for toilets or exterior water faucets. In this home the rainwater harvesting system supplies 100% of the irrigation water and 100% of the water for all toilets and the washing machine. This dramatically reduces the use of city water and also helps with managing drainage around the homes’ perimeter.

Rainwater harvesting captures, stores, and diverts rainwater for later use. The captured water is used for landscape irrigation because the water is free of salts and other harmful minerals and does not have to be treated. Capturing rainwater for the landscape not only makes great use of a valuable resource, it can also save money on the water bill.

Harvesting rainwater not only reduces the demand on our city and state’s water supply, it can also prevent flooding and erosion by slowing runoff and allowing it to soak into the ground. Reducing run-off helps to reduce the contamination of surface water with sediments, fertilizers, and pesticides in rainfall run-off.

For each 1,000 square feet of the roof area or catchment surface of your home, a harvesting system can collect approximately 620 gallons per 1 inch of rain fall.

Catchment is the surface of your roof that rain falls onto and collects from. The catchment area a home is larger than the square footage of a floor plan. It includes garage, covered deck area, and the amount of eave overhang. The vertical slope of your roof does not increase your catchment area, so only the "footprint" of the roof should be considered.

(photo by Yuliya Libkina: Rain In Summer)