Septic and Garbage Disposals & Bedroom Count FAQs

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We would like to extend special thanks to Zackary Seabury, the Health Agent from the Town of Mashpee, Massachusetts for giving us permission to share with you this very helpful Q&A!  As with all regulations, please check directly with the board of health in the town where the property is located for any specific local regulations that might apply.

Can I add more bedrooms/bathrooms to my house [that has a septic system]?

The addition of bathroom is not considered an increase in flow and does not require a septic upgrade; however, the addition of a bedroom OR any space that meets the definition of a bedroom in Title 5 would be considered an increase in flow. (See “What is a bedroom?”)  When determining bedrooms, there are three Codes in Massachusetts to consider.  The first is Title 5 (310 CMR 15) – this regulation is for the septic design flow for the facility which, for residential properties, is based on 110 gallons per a day per a bedroom.  The next is the Building Code 780 CMR, and the third is 105 CMR 410.000: Minimum Standards of Fitness for Human Habitation.

What is considered a bedroom?

The requirements of a bedroom are determined by state codes; however, individual towns can enact more stringent requirements, above and beyond the following:

  • Two means of egress*.  One must go directly to the outside of the home.  This is the emergency egress.
  • A window for natural light and ventilation.  The glazing and opening size of the windows is determined by the total square footage of the usable floor space.
  • Minimum of 70 square feet of floor space
  • Minimum height from floor to ceiling of 7 feet
  • Two (2) electrical outlets or an outlet and a light fixture
  • Fire Safety
  • Opening protection from garage
  • Private access.  The room cannot be a throughway to another room.
  • Floor-to-ceiling height below average ground grading.

*Building Code 780 CMR requires that two forms of egress from a bedroom are provided.   The egresses usually consist of an interior door leading into the rest of the facility and a window to the outside (the emergency egress).  The requirement allows for at least one exit directly to the outside of the home. This allows the occupant to escape the bedroom from two routes during an emergency.  It also allows emergency personnel access from the outside.

Are garbage grinders/disposals allowed with septic systems?

Per 310 CMR 15.223(1)(c), garbage grinders/disposals are permitted when the minimum liquid capacity of the septic tank is at least 200% of the design flow with a minimum tank size of 1,500 gallons, and when a two compartment tank or two tanks in series are provided.  Soil Absorption System (SAS) area requirements increase by 50% when garbage grinders are installed and the system shall be upgraded to meet such requirements prior to the installation of a garbage grinder.  Domestic garbage grinders are prohibited in facilities which include an elevated septic tank constructed in accordance with 310 CMR 15.213.

Courtesy of the Mashpee MA Board of Health

16 Great Neck Road North, Mashpee, MA  02649

Office:  508.539.1400 X8553

Email: Zseabury@mashpeema.gov