Water Harvesting for Landscape Irrigation
Rosalind Haselbeck & Rich Alianelli
Building Green Futures Inc. CCSE
April 19, 2012
Introduction: Who we are
Water Run-off: developed vs. natural
Source: http://www.coastal.ca.gov/nps/watercyclefacts.pdf
Water Use, San Diego
http://www.savewateroceanside.com/conservationtips.asp#graph
Rainwater Harvesting
Components of Rainwater Harvesting for Irrigation
Roof catchment area
Gutters & downspout
Storage
Tank
Overflow Pump
To drip system/hose
Benefits of Rainwater Harvesting
• Reduces personal water bills
• Provides naturally soft, neutral pH water
• Conserves water
• Conserves energy
• Erosion and flood control
• Protects our beaches and rivers
Estimating Supply & Demand
Source: Building Green Futures (www.buildinggreenfutures.com)
Above-ground Tanks
Source: RainHarvest Systems
Source: BH Tanks Inc. Source: Bushman Tanks USA
Source: Tankworks Australia
Below-ground Tanks
Source: Graf Rainwater Tanks
Source: Rainwater Collection Solutions
Source: Xerxes Fiberglass Tanks
Source: Atlantis Water Management
Urban Rainwater Harvesting
A Rainwater Pillow
Source: Building Green Futures (www.buildinggreenfutures.com)
Source: Building Green Futures (www.buildinggreenfutures.com)
2) 8,500 gallon
below-ground
system with a
geothermal loop
field and barrels
above ground
Underground Rainwater Storage:
8,000 gallons in Graf Carat
Tanks
Corrugated
steel tank with
10,000 gallon capacity
Using Earthworks
Greywater Recycling
• Background
• Clothes washer systems
• Whole house systems
• Constructed wetlands
• Indoor non-potable
Why Use Greywater?
• Reduce personal water bills
• Conserve water & energy
• Convert potential pollutants into nutrients
• Reduce strain on treatment or septic systems
• Enhance water quality and recharge groundwater
• Conserve aquatic ecosystems
• Grow plants!
Greywater Numbers
• San Diego homes use 14 HCF water per month
• 14 HCF = 10,472 gallons
• Greywater ~ 50% indoor water use
• By code, 40 gallons per day/occupant
• 3 bdrm house 4,800 gallons greywater/month
• Outdoor use > 50% total water
Defining Greywater
• Greywater = Washwater
• Excludes toilet wastes and kitchen scraps
• Provides Phosphorus, Nitrogen, Potassium
• Greywater systems are onsite wastewater treatment systems using subsurface irrigation
Why Use Greywater?
• Reduce personal water bills
• Create a sustainable landscape
• Convert potential pollutants into nutrients
• Conserve water & energy
• Reduce strain on treatment or septic systems
• Enhance water quality and recharge groundwater
Energy Down the Drain
Source: NRDC “Energy Down the Drain” 2004
Energy intensity = energy required to use a
specific amount of water in a specific location
water heaters
pump stations
pressurizing water
(car wash
Energy Savings with Low Flow Shower Head
Years Rated flow rate, gal/mim
Actual flow rate, gal/min
Estimated energy use per household kWh/yr
Energy savings with low flow 2.5 gpm
1994 to present
2.5 1.7 1,128
1980 - 1994 3.0 2.0 1,328 200/$34*
Pre 1980 5.0 – 8.0 4.3 2,855 1,727/$294*
Source: NRDC “Energy Down the Drain” 2004
* Based on average 17 cents per kWh tier two
Combining Water Harvesting with Indoor Conservation
Water Harvesting Benefits
• Saving water saves energy and reduces air pollution
• The more than 60,000 water systems and 15,000 wastewater systems in the United States
• are among the country’s largest energy consumers, using about 75 billion kWh/yr
• nationally—3 percent of annual U.S. electricity consumption
• Energy intensity = energy required to use a specific amount of water in a specific location
Greywater replenishes groundwater
& enhances soil fertility
Designing a Greywater System
• Minimum irrigation area (code)
• Actual greywater production
• Soil and percolation rate, slope
• Plant choices and water requirements
Soil Texture
Largest minimum area = 192 sq ft/ 160 gal/ day
Estimating Greywater Production
Fixture GPM Uses/day Occupants Gal/day
Lav faucet 2.5 0.5 min
5 each 2 12.5
Shower 2.5 8 min
1 each 2 40
Clothes washer
20 gal per load
0.65 8.5
Total gal/day
61
Weekly 427
Yearly 22,186
Sizing Greywater Irrigation Area: Summary
• By code 3 bdrm house 160 gal/day; 1,120/wk
• Maximum area for minimum requirement (clay soil) = 192 sq ft/160 gal
• More typical ~ 350 - 700 gal/wk
• Can irrigate ~ 7 - 15 trees and shrubs (500 – 800 sq ft)
Plant Considerations
• Fruit trees and
ornamentals best citrus, banana, apple,
plum, guava
• Groundcovers and turf with
dripperline
• Laundry soap cautions
Code and Permit Issues
• 1603A.1.1 Clothes Washer System (may be installed without a permit if in compliance)
• Follow 12 guidelines; don’t alter existing plumbing
• May not result in ponding or run-off • If released above-ground requires >/= 2” mulch • Minimize contact • Operations & maintenance manual • Permit triggers: cutting pipe, using pumps, >250
gallons/day
Laundry to Landscape
• Indoor plumbing
• Outdoor piping
• Test, “tune”, label
3-Way Valve & Washer Hose
More Complex Systems
• Greywater stub outs
• Whole house
• Constructed wetlands
• Non potable indoor use
Greywater Stub outs
• Greywater stub outs enable greywater distribution systems to be installed later
• Lowers economic hurdle for occupancy
• Stub out may be in anticipation of new system types
Whole-house Greywater System for Irrigation
including 3,000 gallon Rainwater Cistern
Water treatment: Constructed Wetland
Cost Benefit Summary
System Cost (Range) Gallons Saved Per Year
Laundry to Landscape $500 - $2,500 2,000 - 10,000
Branched Drain (showers)
$1,000 - $3,000 15,000 - 30,000
Whole house Pump/dripperline
$4,000 - $7,000 35,000 - 60,000
Whole house wetland
> $5,000 35,000 - 60,000
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