Supplement to Regulation 29 and Schedule 9 - Wastewater system loading rates

This factsheet is designed to be read in conjunction with Regulation 29 and Schedule 9 of the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974 (Regulations).

This supplement does not cover every possible application and system designers are asked to contact the Water Team of the Environmental Health Directorate
for further information if a particular use premises type is not listed in this factsheet.

The following table forms the Department of Health WA’s assessment criteria for systems assessed under the Regulations.

Residential premises

The sizing of residential premises hydraulic loading is based on Schedule 9 of the Regulations. For residential premises with 6 or more bedrooms, the hydraulic loading will be sized basing on the expected occupancy rate and the design flow rate of 150L/person/day.

Table 1: Hydraulic loading rates for residential premises

Type of residential premises Number of bedrooms Volume of wastewater (L/day)
Standard residential dwelling
2 or less 564
3 761
4-5 829
6 or more 150L/day
Local government to determine the expected occupancy rate.
Ancillary accommodation sharing a common system with the main residential dwelling The combined hydraulic loading is based on the total combined number of bedrooms (ancillary dwelling PLUS main residential dwelling) and sized as a "Standard residential dwelling" (as above).

  • 3 bedroom main dwelling PLUS 2 bedroom ancillary accommodation = 5 bedroom system (829L/day)
  • 4 bedroom main dwelling PLUS 2 bedroom ancillary accommodation = 6 bedroom system (150L/person/day)
Aged home accommodation 2 or less 564
3 761
4-5 829
Developments with communal system Hydraulic calculation basing on actual occupancies can be permitted if local government planning approval sets occupancy limits for the entire development.

Please note that the sizing of septic tanks must still be done in accordance with Regulation 28 of the Regulations and the sizing method is different from what is prescribed in Table 1.

Non-residential premises

The wastewater system loading rates prescribed in Regulation 29 are limited to a number of broad applications. The purpose of this fact sheet is to provide designers of wastewater and associated disposal systems with a more comprehensive list of equivalent premises and uses. The figures below are to be read in conjunction with Regulation 29(1) and are based on an 8 hour day.

Table 2: Human waste hydraulic loading rates

Type of premises (Regulation 29) Equivalent Use Combined Flow (L/person/day)
Hotel Minesite accomodation camp units 180
Motel   140
School (boarding)   140
School (day) Child care centre (6 hours contact time) 45
Public Building
(Frequent use)

Bakery sit in customers (per sitting)
Café sit in customers (per sitting)
Place of worship (with cooking and catering facilities)
Health centre staff (non-showering)
Minesite office facilities
Offices (non-showering staff)
Restaurants sit in customers (per sitting)
Winery sit in customers – Café and food catering facilities (per sitting)
Warehouse (non-showering)
Workshop (non-showering)

Public Building
(Infrequent use)
Airport (Non-staff)
Place of worship (with no cooking facilities)
Community hall
Hardware stores
Health centre patients (non-showering)
Petrol station customers
 Caravan Parks 3 persons / caravan park bay 140
2 persons / tent site 140
Park homes / chalets / Standard short-stay holiday houses
2 or less bedrooms/dwelling
3 bedrooms/dwelling
4 or more bedrooms/dwelling

Large short-stay holiday houses (>6 persons) /
Eco-tourism accommodation facilities

Swimming Pool   15
Drive-in theatres 2 persons per car 10
Factories & shops
(an 8 hour day)

Bakery Staff
Café staff
Caravan park staff member (not living onsite
Gym (with showers)
Health centre patients (using shower facilities)
Office staff (using shower facilities)
Restaurant staff
Warehouse staff (using shower facilities) 
Workshop staff (using shower facilities) 
Construction camps (temporary)   45
Clubs Men's shed 15
Clubs (licensed)   35

There are other types of wastewater generating activities that are not specified by Regulation 29. Under these circumstances the following will apply:

Table 3: Commercial / industrial waste hydraulic loading rates

Wastewater Source Examples Activity Total Flow (L/day)
Food premises / food production Cafés, 
Bakeries and the like.
Wastewater generated from cooking and food production operations
(eg. takeaway food preparation, offsite catering food preparation, equipment and floor wash down) - excludes personal hygiene and loading for sit in customers.
Refer to Note 1
Commercial waste streams Winery
Bottle rinsing
Wash down
System must be separate and not combined with any human waste stream.

Refer to Note 1
Non-human waste systems Washdown bays
Dog kennels
Horse stables
1) System owner to propose wastewater / liquid waste hydraulic loading. Hydraulic loading must be based on peak flow events. The following controls will be implemented:
  • Metering of wastewater / liquid waste volumes produced
  • System owner to ensure the maximum capacity of the system is not exceeded

More information

Environmental Health Directorate
Department of Health
PO Box 8172
Telephone: (08) 9222 2000
Fax: (08) 9388 4910

Last reviewed: 31-05-2021
Produced by

Environmental Health Directorate