Sewage System Types

Class 2 Sewage System

A Class 2 sewage system is designed to dispose of the greywater component of the sewage waste from domestic plumbing. A Class 2 sewage system is usually used in conjunction with a Class 1 sewage system and a building permit for a sewage system is required.

A Class 2 sewage system shall not be constructed where the total daily design greywater flow exceeds 1 000 L/day. This is calculated based on the fixture units discharging to the system. If the water supply system is pressurized, the total daily sewage flow is calculated at 200 L per fixture unit and 125 L per fixture unit where there is no supply of pressurized water.

A Class 2 sewage system must maintain minimum vertical and horizontal clearances.

The bottom of the greywater pit shall be a minimum of 0.9 m above the high ground water table and 0.6 m above rock or soil with a percolation rate > 50 minutes/centimetre.

The loading rate to the side walls shall not be greater than the value calculated using the formula: LR = 400 ÷ T

Where: LR = Loading rate of the sidewalls in Litres per day
              T = Percolation rate of the receiving soil

Further information can be accessed by visiting the Ministry of Municipal Affairs and Housing Building and Development Branch Website.