Division B
Section 8.4. Class 2 Sewage Systems
Section 8.4. Class 2 Sewage Systems Copy linkAdd bookmark
8.4.1. General Requirements Copy linkAdd bookmark
8.4.1.1. Scope Copy linkAdd bookmark
(1)This Section applies to the construction of a Class 2 sewage system.
8.4.1.2. Application (See Note A-8.4.1.2.) Copy linkAdd bookmark
(1)A Class 2 sewage system shall be designed only for the treatment and disposal of greywater.
(2)The total daily design flow for a Class 2 sewage system shall be calculated based on the fixtures discharging to the system as follows:
(a)200 L per fixture unit where there is a supply of pressurized water, and
(b)125 L per fixture unit where there is no supply of pressurized water.
8.4.2. Design and Construction Requirements Copy linkAdd bookmark
8.4.2.1. Construction Requirements Copy linkAdd bookmark
(1)The bottom of the pit shall be at least 900 mm above the high ground water table.
(2)The pit shall be constructed in such a manner as to prevent the collapse of its sidewalls.
(3)Any material used to support or form the sidewalls of the pit shall be an open jointed material of a type that will permit leaching from the pit.
(4)The pit shall be provided with a tight, strong cover that shall remain over the pit except when it is necessary to remove it for purposes of adding greywater to or removing greywater from the pit or for purposes of maintenance of the pit.
(5)The earth around the perimeter of the pit shall be raised or mounded to a height of at least 150 mm above ground level.
(6)The surface of the ground in the area of the pit shall be so graded that surface drainage in the area will be diverted away from the pit.
(7)The pit shall be surrounded on all sides and on its bottom by at least 600 mm of soil having a percolation time of less than 50 minutes.
8.4.2.2. Maximum Sewage Flow Copy linkAdd bookmark
(1)A Class 2 sewage system shall not be constructed where the daily design greywater flow to the system exceeds 1 000 L/day.
8.4.2.3. Sizing Copy linkAdd bookmark
(1)A Class 2 sewage system shall be designed and constructed so that the loading rate to the side walls shall be not more than the value calculated using the formula,
400 L
R
T =
where,
LR = loading rate of the sidewalls in litres per day/m2, and
T = percolation time.