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RAINWATER HARVESTING STORAGE WORKSHEET
WEATHER STATION:Saltspring Island
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Optimize your storage volume
PROJECT NAME:Gabriola
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DATE:July 20, 2017
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INPUTS
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MONTHJANFEBMARAPRMAYJUNJULAUGSEPTOCTNOVDECTOTAL
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Environment Canada Precipitation (mm)
162.099.089.057.043.037.023.028.033.094.0168.0154.0987.0
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Household Usage (imp gals) - - - - - - - - - - - - -
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Irrigation/Outside Usage (imp gals) (make-up)
1,000 1,000 1,000 1,000 1,000 5,000
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Total Usage (imp gals) - - - - 1,000 1,000 1,000 1,000 1,000 - - - 5,000
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OUTPUTS
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MONTHJANFEBMARAPRMAYJUNJULAUGSEPTOCTNOVDECTOTAL
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Precipitation Received from Roof (imp gals) 6,633 4,054 3,644 2,334 1,761 1,515 942 1,146 1,351 3,849 6,879 6,306 40,413
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Start of Month in Storage (imp gals) (Last Dec.)
10,000 10,000 10,000 10,000 9,834 9,094 8,109 4,551 1,198 0 1,349 5,728
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Overflow Volume - wastage (imp gals) 4,133 1,554 1,144 0 0 0 0 0 0 0 0 0 6,831
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End of Month in Storage (imp gals) (make-up) 10,000 10,000 10,000 9,834 9,094 8,109 4,551 1,198 (1,951) 1,349 5,728 9,533
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SELECTED TANK CAPACITY (IMP GALS) 10,000
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ROOF AREA (SQFT) 2,500
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ROOF EFFICIENCY0.8
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ANNUAL OVERFLOW VOLUME (WASTAGE)17%
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ANNUAL MAKE-UP WATER (SHORTFALL) -5%
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Notes:
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- Performance based on monthly averages.
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- Bracketed numbers indicate rainwater shortfall
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- Precipitation includes snowfall
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- Useful links:
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*Rainwater Guide for Homeowners - CMHC
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 *Irrigation Discussion
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 *Irrigation Calculator
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 *Premierplastics.com
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