Western Australian Current Regulations

HEALTH (TREATMENT OF SEWAGE AND DISPOSAL OF EFFLUENT AND LIQUID WASTE) REGULATIONS 1974 - REG 49

49 .         Requirements for receptacles for drainage

        (1)         The receptacles for drainage referred to in regulations 47 and 48 shall —

            (a)         be constructed in the manner and using the materials —

                  (i)         set out in Schedule 7; or

                  (ii)         approved by the Chief Health Officer;

                and

            (aa)         if they are part of an apparatus of a kind to which an adopted Code applies, be constructed in compliance with that Code; and

            (b)         subject to subregulation (5) be constructed so that effluent or liquid wastes will not be discharged into the ground at a distance less than 30 m from any well, stream or underground source of water intended for consumption by humans; and

            (c)         not be constructed within 6 m of any subsoil drainage system or open drainage channel; and

            (d)         be located where approved; and

            (e)         if on residential premises, comply with subregulation (2) or (3).

        (2)         On residential premises with a combined system (other than blocks of flats or units with more than 4 bedrooms) —

            (a)         that have an alternating system, the type, minimum number and size of receptacles for drainage and the minimum infiltrative area of those receptacles shall be as specified in the Table to this regulation in relation to the number of bedrooms of the premises and the classification of soil on the premises;

            (b)         that have a non‑alternating system, the receptacles for drainage used shall provide a minimum infiltrative area of twice the minimum infiltrative area required under the Table to this regulation if the system was an alternating system.

        (3)         On residential premises where subregulation (2) does not apply, the receptacles for drainage on any apparatus shall provide a minimum infiltrative area determined in accordance with the following formula —

                where —

        A = minimum infiltrative area (m ² )

        V = volume of wastewater (litres), calculated under Schedule 9

        L.I.R. = loading infiltration rate, in accordance with Schedule 8.

        (4)         An approving body may approve of the use of a type or minimum number and size of receptacles for drainage for drainage that vary from those specified under subregulation (2)(a) provided that —

            (a)         an equivalent minimum infiltrative area to that provided under subregulation (2)(a) is achieved; and

            (b)         structural integrity is maintained.

        (5)         An approving body may approve the construction of a receptacle for drainage, at a distance less than 30 m from a well, stream or underground source of water referred to in subregulation (1)(b) where the Chief Health Officer is satisfied that such construction would not cause any risk to public health.

Table
For combined systems, other than blocks of flats or units with more than 4 bedrooms

Number of bedrooms	Soil classification
	Sand			Loams or gravels
	Minimum infiltrative area (m 2 )	French, leach or evaporation drain (number x length)	Soak wells	Minimum infiltrative area (m 2 )	French, leach or evaporation drain (number x length)
2 or less 3 4 or more	18.8 25.4 27.6	2 x 6m 2 x 8m 2 x 9m	3 4 4	28.2 38.1 41.5	2 x 9m 2 x 12m 2 x 13m
NOTES 1.         French drain sizes are calculated on the basis of the standard dimensions of 400 mm effective depth and 600 mm internal width. 2.         Leach drain sizes are calculated on the basis of the standard dimensions of 600 mm effective depth and 400 mm internal width. 3.         Evaporation drain sizes are calculated on the basis of the standard dimensions of 410 mm effective depth and 610 mm internal width.

        [Regulation 49 inserted: Gazette 15 Dec 1989 p. 4550‑1; amended: Gazette 12 Nov 1993 p. 6143; 29 Jul 1997 p. 4080‑1; 7 Jan 2005 p. 69; 10 Jan 2017 p. 287‑8.]