Part VIII of the Ontario Building Code governs the design, construction, operation and maintenance of Sewage Treatment Systems up to a capacity of 10,000 Litres per day on one individual lot. (These are sometimes referred to as 'septic systems')

Sewage Systems greater than 10,000 Litres per day, or if a single property contains several small systems (less than 10,000 L/d each) but the combined capacity of the systems exceeds 10,000 L/d, all those systems are subject to Ministry of Environment approval regardless of their individual sizes.

The Ontario Building Code specifies the minimum requirements of approval for 5 different Classes of Sewage Treatment System.

Class 1 Sewage System - composting toilet, pit privy, vault privy etc

Class 2 Sewage System - leaching pit (used for the treatment and disposal of
grey water only)

Class 3 Sewage System - cesspool (used for the disposal of the contents of a
Class 1 sewage system only)

Class 4 Sewage System - conventional - septic tank and leaching bed
alternative - septic tank and treatment unit (used for the treatment and disposal of all wastewater)

Class 5 Sewage System - holding tank (contents must be pumped as often as is required)
This system is permitted only by exemption under the Building Code. Contact the Health Unit for details.