Onsite Wastewater Disposal Systems, Kaipara District Council

Onsite Wastewater Disposal Systems

If you're looking for essential information to help you understand and maintain your Onsite Wastewater Disposal System (OWDS) while safeguarding our environment - you have come to the right place. 

Who needs an OWDS?

Properties not connected to the Council wastewater system must have an OWDS. These properties will typically have a septic tank, or an aerated wastewater treatment system. (AWTS).

Installing, upgrading or replacing an OWDS

If you are installing a new system or upgrading, check the consent requirements.

There are many different systems and the type you require depends on various factors. It needs to be fit for purpose and you will need to engage a qualified person to determine what system your property requires.

The prices of setup and on-going maintenance costs will vary between different systems.

Once the system has been installed and is operational, the Kaipara District Council Wastewater Drainage Bylaw will apply: https://www.kaipara.govt.nz/bylaws 

Please review your onsite wastewater system if:

  • renovations are being undertaken on your home
  • the number of occupants in your home has increased
  • your bach becomes your permanent home
  • you start to host a lot of visitors.

The above changes mean more water will flow through your system. This puts more strain on how well your tanks and disposal field can treat your sewage and wastewater.

Maintaining your system

Avoid harming the environment by keeping your OWDS maintained

As a property owner, you are responsible for maintaining your onsite wastewater system and knowing how it works. Please refer to Water New Zealand website for information on how to take care of your system. Please also see the below information.

Septic tanks

A septic tank must be pumped out (desludged) regularly every three years, to remove excess sludge and scum. If the septic tank is not desludged often enough, excessive solids and fats will cause clogging of your disposal system and early failure. 

Replacing a failed disposal system can cost over ten times as much as getting a septic tank desludged.

Top tips:

1.       A septic tank is desludged by putting a suction hose through the access lid – not down the mushroom vent – so keeping the access lid accessible and not covered over is very important.

2.       Never wash out your tank after it has been desludged, as the bacteria and solids left behind are required to restart biological activity.

black and white diagram of a standard septic tank design

diagram of an older style septic tank and soakage trench system

Aerated Wastewater Treatment Systems

Inspect these annually or as specified by the manufacturer

The term ‘Aerated Wastewater Treatment Systems (AWTS)’ covers a range of types of on-site treatment systems that provide additional treatment to septic tank effluent. Their mechanical pumps require regular maintenance and a continuous power supply. In general, an AWTS has three parts which may be housed in a single unit or split into more than one unit.

Generalised diagram of an AWTS system

Aerobic (aerated) treatment plant


Be aware that your system could malfunction at any time. Signs your system has failed include:

  • broken tank lids
  • scum and sludge build-up in your septic tank
  • strong odour coming from the septic tank or disposal field
  • slow running drains or toilets
  • a blockage or overflow of sewage waste
  • effluent or wastewater on the ground around the septic tank and disposal field area, along with murky or smelly puddles on your property
  • grease trap is fully blocked or overflowing.

We recommend installing a WW filter in the septic tank to prevent premature failure of the effluent field caused by large articles flowing from the septic tank and blocking drip lines etc.  A fitted filter may allow a longer period between septic tank de-sludges.


  • overloading your system with too much water
  • letting rain into your system
  • pouring any toxic/strong chemicals (paint, oil, grease, thinners, pesticides down any drains)
  • flushing any products other than standard toilet paper down the toilet – this means no ladies feminine hygiene products, cigarette butts, wet wipes etc.
  • discarding any drugs down the toilet or sink
  • using strong cleaners such as (bleach, Canestan, Napisan, strong citrus or alcohol base)
  • tipping chlorine, anti-septic, anti-bacterial, or disinfectant type products down the drain
  • using chemical drain cleaning products to clear a blockage – call a plumber
  • putting coffee grinds down the sink drain.

Beware around sink garbage grinders.  If a grinder exists, don’t discharge high volumes of scraps, especially carbohydrates, bones or fats and oils into it.


  • use environmentally friendly/natural soaps and cleaners
  • check all your cleaning products to see if they are suitable for Septic Tanks and AWTS
  • scrape all plates and dishes to compost/rubbish, removing as much food/fat as possible
  • repair/fix all leaking taps as soon as possible
  • use phosphate free or low phosphorus laundry detergents
  • find a contractor online or see our Suitably Qualified Persons List for advice
filter clogging failed soakage field clogged gully trap

Suitably Qualified Persons List

As a homeowner, it is your responsibility to ensure that you coordinate the inspection and maintenance of your onsite wastewater disposal system in accordance with the bylaw. The contractor is responsible for carrying out this service in accordance with best practice. Council is not responsible for any inspection, maintenance or repair works to your system or for any liability in relation to any service that is provided by the contactor.

Kaipara District Council Wastewater Drainage Bylaw