Number of bedrooms
Number of residents
- Sand and gravel
- Sandy loam
- Clay loam
- Light clay
- Medium/Heavy Clay
- Absorption trench
- Evapotranspiration bed
- Wisconsin mound
- Spray Irrigation
- Sub-surface irrigation
Does the system prevent the spread of disease by micro-organisms? (1)
Does the system prevent the spread of foul odours? (2)
Does the system prevent the contamination of water? (3)
Does the system prevent the degradation of soil and vegetation? (4)
Does the system discourage insects and vermin? (5)
Does the system ensure that persons do not come I to contact with untreated sewage or effluent (whether treat or not) in their ordinary activities on the premises concerned? (6)
Does the system minimise any adverse impacts on the amenity of the premises and surrounding lands? (7)
Does the systems provide for he re-use of resources (including nutrients, organic matter and water? (8)
Is the effluent disposal area greater than 100 m to permanent surface waters? (9)
Is the effluent disposal area greater than 250 m to domestic groundwater? (10)
Is the effluent disposal area greater than 40 m to other waters (eg intermittent waterways, dams)? (11)
Is the effluent disposal area greater than 6 m up/3m down to driveways & property boundaries? (12)
Is the effluent disposal area greater than 15 m to dwellings? (13)
Is the effluent disposal area greater than 3 m to paths and walkways? (14)
Is the effluent disposal area greater than 6 m to swimming pools? (15)
Is the effluent disposal area greater than 6 m up/ 3 m down to pools, property boundaries, driveways & buildings? (16)
Is the effluent disposal area greater than 12 m up/6m down to the property boundary? (17)
Is the effluent disposal area greater than 6 m up/ 3 m down to pools, driveways and buildings? (18)
Is the lid, manhole and inspection openings undamaged and in place? (19)
Is the tank accessible? (20)
Is the tank undamaged? (21)
Does the tank need a pump-out? (22)
Have service reports been sent to Council? (23)
Is the irrigation line buried? (24)
Is there sufficient irrigation area? (25)
Has a testable backflow containment device being installed (for new systems)? (26)
Is the system operational at the time of inspection? (27)
Eg - chlorine tablets, UV lamp
Are irrigation warning signs present? (28)
Is effluent being evenly distributed? (29)
Are garden hoses and fittings being used for irrigation? (30)
If there is a grease trap, is it satisfactory? (31)
Is greywater being disposed of satisfactorily? (32)
Is the disposal area showing signs of stress? (33)
Is the disposal area failing? (34)
Is there a pump-out contract? (35)
Is there a draw line with a cam lock? (36)
Does the operator have pump-out receipts? (37)
Is greywater being disposed of satisfactorily? (38)
- Issue Approval - 5 years
- Issue Approval - 3 years
- Issue Approval - 1 year
- Works required letter
- Failing System - Local Government Order
- Prevention Notice ( POEO Act)
- Works Satisfactory - Proceed
In 1997, an incident occurred where wastewater was found to be discharged into Wallis Lake, near Port Macquarie. The discharge came from a number of domestic septic tanks. As the Lake was used for aquaculture, an outbreak of Hepatitis A occurred, resulting in 444 people contracting the disease and one fatality.
As a result, a review was undertaken and it found that councils were best placed to inspect and regulate the use of on-site sewage management system. Changes were made to the Local Government Act 1993 ( the “Act”) to require everyone with an on-site sewage management systems to obtain an approval to operate the system.
The maximum time that an approval can be granted is five years and an approval is not transferable on the sale of a property.
There are a number of simple things that you can do to protect your on-site sewage management system:
• use a sink strainer to reduce waste reaching your septic tank;
• clean the grease trap regularly (where fitted);
• don’t discharge bleach, whiteners, nappy soakers etc into the system;
• don’t discharge hygiene products, condoms, tampons, nappies and cotton buds into the system;
• don’t use more than recommended amounts of disinfectants and detergents;
• repair leaking taps and cisterns;
• have the sludge pumped out every 4-5 years;
• grow grass in your effluent disposal area and keep it regularly mown;
• divert stormwater away from the area;
• don’t drive or park vehicles over the area; and
• keep livestock out of the area to avoid compacting of the soil.
If the system becomes smelly, flush a cup of lime (calcium oxide) down the toilet each day for 7 days. This will reduce the pH and encourage bacterial growth, which reduces the odour.
If today’s inspection found that your system is not operating satisfactorily, it may not mean that you need to replace or upgrade your tank. Often the only work required is to repair or replace the effluent disposal area.
Depending on the circumstances, Council may:
• ask for work to be done;
• ask you to submit details of work that you propose to do so that the system complies;
• issue a Local Government Order to carry out work or submit details;
• issue an Environmental Protection Notice under the Protection of the Environment Operations Act 1997;
• take other regulatory action.
The design of an effluent disposal system is based upon two key factors - the amount of wastewater generated by the household, and the soil type.
WASTEWATER – the amount of wastewater that is generated by a household is generally determined to be 290 litres per bedroom (plus any study) per day for dwellings on mains water supply, and 230 litres per day for tank supply.
SOIL – the type of soil is used to determine how much area is required to absorb the effluent produced by the household. The soil type is determined from 500 mm below the effluent disposal layer and is classified into one of six general categories: gravels & sands; sandy loams; loams; clay loams; light clays and medium to heavy clays.
SOIL TYPE DESIGN IRRIGATION RATE DESIGN LOADING RATE
Gravel & Sands 35 35
Sandy Loams 35 25
Loams 28 15
Clay Loams 25 10
Light Clays 20 8
Medium to heavy clays 15 5
Information on how to determine soil classifications can be found at:
The most common effluent disposal methods are absorption trenches (generally associated with septic
tanks) and spray irrigation.
ABSORPTION TRENCHES are generally used to dispose of primary treated effluent (that is, effluent that
has only been treated by detention).
To determine the size of absorption trench required, the following formula is used:
Length of trench = daily wastewater flow
design loading rate x width (m)
For example, for a four bedroom home with sandy loam soil:
25 x 0.6
= 77.3 metres
Other important factors to take into consideration when designing an absorption trench are:
• individual trenches cannot exceed 20 metres in length;
• trenches must be a minimum of 1 metre apart;
• maximum width of a trench is 0.6 metres; and
• bottom of trenches must be level.
SPRAY IRRIGATION is used to dispose of secondary treated effluent, most commonly from an aerated
wastewater treatment system (AWTS) where disinfection occurs.
To determine the size of spray irrigation area required, the following formula is used:
Area = weekly wastewater flow
design irrigation rate
For example, for a four bedroom home with loam soil:
= 1160 x 7
= 290 square metres
The irrigation line must be buried so that the moveable length of line cannot extend beyond the approved
SUBSURFACE IRRIGATION may be used with secondary effluent that hasn’t been disinfected. The area required is determine in the same way as that for spray irrigation.
In both cases, Council’s policy requires you to designate a reserve area that could be used in the future if the effluent disposal area is damaged or requires resting.
Further information is available on Council’s website at www.thehills.nsw.gov.au or call Council during office hours on 9843 0555 and speak to an Environmental Health Officer.