Water Reuse Handbook - the Public Building Commission of Chicago

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Water Reuse Handbook Planning for a Water Reuse System 32 : Public Building Commission of Chicago August 2011
Planning for a Water Reuse System: Planning for Rainwater Harvesting Planning for Rainwater Harvesting System Supply and Demand August 2011 Step 1: Estimate demand Treated rainwater can be reused in many ways, such as flushing toilets and urinals, irrigating landscape areas, or running clothes washers. To inform the rainwater harvesting system’s design, it is critical to consider the end uses of the treated rainwater. The table* to the right lists fixtures that may reuse treated rainwater and their water demands per day per person. Demand for rainwater can typically be calculated by multiplying the number of building occupants by the average daily demand per person for the item (such as for toilet flushing). Demand for clothes washing and irrigation must also be included in this calculation. This number represents the approximate minimum daily rainwater supply (in gallons) needed to support that function. Step 2: Evaluate supply Roof Catchment Calculation The amount of rainwater that may be collected is often constrained by the amount of roof surface available. The amount of roof surface area, based on the needed water volume for the system, is summarized as: Surface area (sf) = Demand (gal)/0.623 * Precip Density (in) * 0.85 • Surface area is the horizontal projection of roof surface in square feet. It is not the actual surface area. Measure the area the roof covers, not the actual roof. • 0.623 gallons is 1 inch of water covering 1 square foot of surface area • Precipitation density is the average amount of rainfall in inches for the time period that the system will be used (monthly or yearly averages) • 0.85 represents the roof’s collection efficiency and accounts for rainwater loss through leakage, evaporation, roof composition, etc. Roof coefficients typically range from 0.80 to 0.85. Storage Sizing Calculation The maximum amount of rain that can be collected can be calculated as such: Run-off (gal) = A * (Rainfall (in) - B) * Roof Area (sf) Fixture Flow Rate (per use) Water Reuse Handbook Average Average # Daily Uses/Day (per Demand per person) Person (gal) Toilet (HET) 1.28 gpf 5.1 uses/day 6.5 gal. Urinal (HEU) 0.5 gpf 5.1 uses/day 2.55 gal. Estimating Demand for Rainwater. *May vary based on application Source: http://www.epa.gov/watersense/pubs/indoor.html Public Building Commission of Chicago : 33
Page 1 and 2: AUGUST 2011 Public Building Commiss
Page 3 and 4: Contents Introduction .............
Page 5 and 6: Letter from the Chairman As Chairma
Page 7 and 8: Letter from the Executive Director
Page 9 and 10: Introduction The Public Building Co
Page 11 and 12: Reduced Demand for Potable Water Re
Page 13 and 14: Water Regulations Introduction Exis
Page 15 and 16: Recent Regulatory Developments Augu
Page 17 and 18: Tools and Strategies: Reducing Fres
Page 19 and 20: Tools and Strategies: Reducing Fres
Page 21 and 22: August 2011 VENTILATION 8 FINISH In
Page 23 and 24: Tools and Strategies: Rainwater Har
Page 31 and 32: August 2011 VENTILATION 7 REQUIRED
Page 33 and 34: Tools and Strategies: Greywater Sys
Page 35 and 36: Tools and Strategies: Greywater Sys
Page 37 and 38: Tools and Strategies: Blackwater Sy
Page 39: August 2011 Public Building Commiss
Page 43 and 44: Planning for a Water Reuse System:
Page 45 and 46: Building Operations and Maintenance
Page 47 and 48: Building Operations and Maintenance
Page 49 and 50: Local Case Studies: Beach Houses Be
Page 51 and 52: Local Case Studies: Beach Houses Au
Page 53 and 54: Local Case Studies: Valley Forge Fi
Page 55 and 56: Local Case Studies: Yannell Residen
Page 57 and 58: Local Case Studies: Center on Halst
Page 59 and 60: Local Case Studies: Center on Halst
Page 61 and 62: National/International Examples: St
Page 63 and 64: National/International Examples: Po
Page 65 and 66: National/International Examples: To
Page 67 and 68: National/International Examples: Ha
Page 69 and 70: National/International Examples: Sy
Page 75 and 76: Bibliography “Greywater Reuse in
Page 77 and 78: Bibliography “The Lifesaver Bottl
Page 79 and 80: Definitions Definitions August 2011
Page 81 and 82: August 2011 Water Reuse Handbook Pu
Page 83 and 84: August 2011 Water Reuse Handbook Pu

Water Reuse Handbook - the Public Building Commission of Chicago

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