Collecting the Drops

"Rules of Thumb"

Sanitary Water Usage
  • 10 -25 gallons per person per shift
  • The lower value is used where there are just toilets. A higher value is used where there are toilets, showers, full kitchen services, that is, food preparation and dish washing.
Irrigation Usage
  • Number of sprinkler heads x the flow capacity per head (e.g.; 2.5 gpm x  the duration [minutes] of water application)
  • Inspect the irrigation system during operation to determine if there are leaks from broken sprinkler heads and from water distribution lines.
Wastewater Streams from Water Treatment Operations
  • Reverse Osmosis Reject Flow
    • Reject stream generally ranges from 10 to 50% of the feed to the system depending on the salinity and the desired purity.
    • Reject flow can be higher than the indicated range. RO reject streams can be used as cooling tower makeup if the water is softened prior to the reverse osmosis system.
Cooling Tower Usage
  • Windage Loss
    • Commonly 0.1 to 0.3 % of the Recirculation Rate
    • The tower recirculation rate can be obtained from the manufacturer’s literature and or head versus flow curve for the pump.
Boiler Usage
  • Boiler Blow Down
    • Range of 4 to 8 % of boiler makeup
Other Uses
  • Slab Washing
    • 5 gal/min for each hose
  • 1 drip/second
    • 10,000 l/year or 2,642 gal/year
  • Water Flow Estimation
    • Use a bucket and stop watch


Helpful Links

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Module 1: Water Use and Impacts | Module 2: Water Management Risk Assessment | Module 3: Case Examples and Links
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