Urban Affairs and New Nontraditional Programs

Rainwater Harvesting

System Design

There are several steps involved in creating a suitable rainwater collection system. There are also numerous solutions and methods you can use to create a system.

For best results, consider the following steps:

  1. Ensure that the catchment surface is suitable for collecting quality rainwater.
  2. Ensure roof gutters are installed to the appropriate standards according to the regulation fall and number of outlets.
  3. Install a fireproof mesh or gutter cover system to prevent leaves and debris from blocking outlets.
  4. Fit gutter outlets under the roof gutter to prevent sludge buildup.
  5. Fit rain head to gutters to divert leaves and debris. Use a screen with less than 1 millimeter apertures to reduce mosquito infestations.
  6. Fit insect proof screens to all pipes that hold water and all pipes and openings to and from the tank.
  7. Fit appropriately sized first flush water diverters. Diverter tubes should redirect 0.1 to 0.5 gallons per 10 square feet of roof surface.
  8. Select an appropriate tank based on collection area, rainfall, water use, and climate.
  9. Choose a pump that provides sufficient pressure for desired lift, rise, and run of the water lines and type of irrigation system.
  10. Draw water from the highest point in the tank possible. Floating outflow filtration systems will do this best.
  11. Ensure the system is maintained. Service gutters, rain heads, water diverters, tanks, and pumps regularly.
  12. Insulate and protect all water lines and pumps from freezing temperatures.
  13. Check local ordinances and tax laws to see if you can get tax credits or rebates for installation of your system.

Cost of the System

We have constructed a small, tank system for under $400 (see Figure 1) and 1,500-gallon systems for commercial crops that cost about $3,000, not including the irrigation lines. Your system costs will depend on whether you need some or all of the following:

  • Gutters
  • Downspouts
  • Tank
    • Above ground or in-ground
    • Size
    • Tank material (polyethylene, fiberglass, metal, concrete)
  • Pump
    • Rise of land to irrigation site
    • Lift (if water must be raised out of the tank)
    • Run (greater distances reduce pressure)
    • Pressure tank
  • Filtration
    • Leaf collection
    • First flush diverter
    • Insect screens
    • Inline filters
    • Floating filter
  • Plumbing-pipes and fittings
  • Irrigation supplies

(Adapted with permission from Rain Harvesting Pty Ltd. www.rainharvesting.com)