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We will discuss some strategies for incorporating water harvesting into sustainable landscaping, using example projects to illustrate our points. We will focus on residential systems for outdoor usage but will also touch on commercial applications and non-potable indoor use.
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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