University of Illinois Extension

Quiz

Practice Problems: Sizing Septic Tanks 1

Residential sizing is based on the number of bedrooms and if there is a garbage grinder present. Sizing residential tanks can be found in section 905, Appendix A, Illustration F Commercial sizing is based on gallons of flow expected per day, either by actual use figures; code derived estimates, or approved IDPH estimates. Commercial sizing can be found in section 905, Appendix A, Illustration A. Tank size for commercial sites require a minimum of 750 gallon size for flows less than 500 gallons per day, or 1.5 times the average daily flow for amounts over 500 gallons per day.

Size the septic tank for the following residential situations. 

  1. Practice Problems: Sizing Septic Tanks 1

    A 3 bedroom house with no grinder:

    1000 gallons
  2. Practice Problems: Sizing Septic Tanks 1

    A 3 bedroom house with a grinder:

    1500 gallons
  3. Practice Problems: Sizing Septic Tanks 1

    A 5 bedroom house with no grinder:

    1500 gallons
  4. Practice Problems: Sizing Septic Tanks 1

    A 3 bedroom house with 5 bathrooms:

    1000 gallons