Onsite domestic wastewater systems

If you manage sewage at your property by using an onsite wastewater management system (OWMS) such as a septic tank, composting toilet or secondary treatment system, it is important you're aware of your legal obligations.

The Environment Protection Act 2017 includes a duty focused on prevention, called general environmental duty (GED) that requires the person in management or control of a septic tank system to take all reasonable practicable steps to make sure the system does not pose a risk to human health or the environment.

Under the GED, an owner of a septic system must notify Council as soon as possible after you become aware that your septic system is failing and potentially posing a risk to human health or the environment.

Our Environmental Health Unit can assist in advising how best to rectify any problems you are experiencing.

However, to avoid septic failures, the below principles and Do’s and Don’ts will help:

Maintain your system regularly
Reduce sludge build up in the tank
Keep bacteria working well
Avoid powerful chemicals
Reduce the amount of wastewater you produce
Avoid overloading your system

Do	Don't
Make sure your system can be easily accessed at all times	Build anything over your septic tank, absorption trenches or irrigation field
Desludge the system every 3 – 5 years. How often depends on how much the system is used	Put food waste or grease down kitchen sinks, nor hygiene products down the toilet
Only use septic-safe soaps and detergents: biodegradable and low in phosphate & sodium	Use powerful chemicals like bleaches, whiteners, spot removers, disinfectants etc.
Reduce the amount of waste water you use /Install water saving fixtures/only launder full washing loads	Run your dishwasher and washing machine at the same time
Only grow grass or very shallow-rooted plants over or near wastewater disposal trenches or fields	Grow trees near trenches or your irrigation field that will cast shade over it, or allow tree roots to invade pipework.
Regular mowing of grass over trenches and irrigation fields will help take up the moisture	Drive vehicles over any part of the system, nor allow heavy-footed animals to graze.
Use a licensed plumber to check if your system needs cleaning or unblocking	Allow stormwater to inundate the disposal field. Put in a diversion drain to avoid this
For treatment plants follow all manufacturer’s instructions and manuals	Allow an unqualified person to service your treatment plant (use only a qualified service agent for the system).