Massachusetts General Law (Chapter 176, Acts of 2002, Sec. 3) allows the use of "self-contained, zero discharge, stand-alone composting toilets." Zero discharge means the toilet does not produce an effluent that needs to be pumped out or discharged to a soil absorption system. You do not have to apply for MassDEP approval to install toilets that meet these criteria. All other humus/composting toilets not meeting the above criteria must first be approved by the MassDEP and before the local Board of Health can allow them to be installed. Note that any interior plumbing device must also be approved by the State Board of Plumbers and Gas Fitters before it can be installed in Massachusetts.

You must obtain a Disposal System Construction Permit from your local Board of Health before you install a composting toilet. For homes or businesses that also generate greywater (i.e., wastewater from sinks, showers, washing machines, etc), you still need to install a disposal system consisting of an effluent filter and/or a septic tank and soil absorption system.

Title 5 has the following provisions for greywater and composting toilets systems.

Greywater is subject to the following (310 CMR 15.262):

  • Allows greywater systems for new construction: residential facilities need to demonstrate that a fully complying system can be installed.
  • Reduces the septic tank size to 1000 gallons for residential systems. Septic tanks for commercial and public facilities shall be at least two thirds the size of a septic tank based on the design flows presented in 310 CMR 15.203. An effluent filter system specifically approved by MassDEP and/or the State Board of Plumbers and Gas Fitters for this use may be used in place of the septic tank.
  • Greywater systems for new construction or increase in flows must comply with the nitrogen loading requirements of 440 gallons per acre.
  • Provides an allowable nitrogen loading rate for residential facilities of 660 gallons per acre and up to 770 gallons per acre on a case-by-case as determined by the Department for commercial and public facilities provided there is no discharge of blackwater and the compost is disposed off-site.   
  • Allows a 50% reduction in the SAS when a composting toilet is used.
  • Requires nine inches of cover over the SAS.
  • For remedial upgrades the groundwater separation may be reduced to 2 feet where the percolation rate is greater than 2 mpi or 3 feet where the percolation rate is 2 mpi or less.

Humus/Composting Toilets are subject to the following (310 CMR 15.289):

  • No liquid wastewater discharge from the humus/composting toilet.
  • If the humus/composting toilet produces a liquid by-product that is not recycled through the toilet, the liquid by-product is either discharged through a greywater system on the property that includes a septic tank and soil absorption system, or removed by a licensed septage hauler.
  • An existing cesspool may serve as a leaching pit for greywater subject to restrictions in 310 CMR 15.289.
  • Humus/Composting Toilets are certified for general use in new construction for residential facilities where a system in full compliance with 310 CMR 15.000 could otherwise be installed on the site
  • For commercial and public facilities or private organizations, humus/composting toilets are certified for general use without the need to demonstrate that a system in full compliance with 310 CMR 15.000 could otherwise be installed on the site.
  • The composting system must be designed to store solids for at least two years or as approved by MassDEP. Residuals from the system must be buried on-site and covered with a minimum of six inches of clean compacted soil, collected by a licensed septage hauler, or disposed of in another manner and location approved by the local Board of Health.