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Septic Tank Size Calculator

Calculate the proper septic tank size based on bedrooms and occupants. Essential for new installations and system upgrades.

How to Size a Septic Tank

Septic tank sizing is based on daily wastewater generation and local building codes. The tank must provide adequate retention time for proper treatment.

Sizing Factors

  • Daily Water Usage: Typically 75 gallons per person per day
  • Retention Time: Minimum 2-3 days for proper settling
  • Building Codes: Local codes specify minimum sizes by bedroom count
  • Peak Usage: Account for holiday guests and special events

Standard Minimum Sizes

  • 1-2 Bedrooms: 750-1000 gallons
  • 3 Bedrooms: 1000 gallons
  • 4 Bedrooms: 1200 gallons
  • 5 Bedrooms: 1500 gallons
  • 6+ Bedrooms: Add 250 gallons per additional bedroom

Cite this page as:

Daniel, P. Septic Tank Size Calculator. Available at: https://constructioncalculators.com/septic-tank-size-calculator/. Accessed: October 25, 2026.