Calculation Example: Determining Total Water Supply Fixture Units (WSFU)

Example

A commercial office building restoom contains the following fixtures: 4 flush-valve water closets (WC), 3 wall-hung urinals (flush valve), and 4 lavatories (sinks). Calculate the total simultaneous peak demand using the Water Supply Fixture Units (WSFU) method for public use facilities. Assume the individual WSFU values are: WC=10, Urinal=5, Lavatory=2.

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Calculation Example: Roof Storm Drainage Area Sizing

Example

A flat commercial roof has a total horizontal projected area of 400 m2400 \text{ } m^2. Local climatic data specifies a maximum design rainfall intensity (II) of 100 mm/hour. Calculate the total required storm drainage capacity in Liters per Second (LPS).

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Key Takeaways
  • Gravity is King: Drainage systems depend absolutely on proper slope (2%).
  • Sizing Methodology: Commercial water distribution must be statistically sized using Fixture Units (WSFU) and Hunter's Curve to accurately estimate simultaneous probable peak demands.
  • Health Defenses: Plumbers vigorously defend the pristine potable water supply by completely eliminating toxic Cross-Connections using proper Air Gaps and mechanical Vacuum Breakers.
  • Protection: Traps stop smells from entering living spaces, while Vents stop traps from failing due to pressure changes.
  • Separation: Storm water and Sanitary waste must never mix to prevent overwhelming municipal wastewater treatment plants during heavy rains.
  • Materials Matter: Use PPR or PEX for pressurized potable water and heavy-duty PVC (Series 1000) for sanitary drainage.