Our processes start right at the source.

Auckland’s water comes from varied sources, including dams, groundwater, springs and rivers. Each treatment plant is designed to deal with the sources of water that feed it.

The water from dams in the Hūnua and Waitākere ranges comes from protected areas that are mostly native bush. It requires a relatively low level of treatment to meet water standards. 

Groundwater typically requires an even lower level of treatment, as the raw water is largely free from bacteria and has very low turbidity (cloudiness).

The Waikato River travels through a lot of different environments before the water treatment plant at Tuakau, so it goes through additional treatment processes compared to water from our dams and groundwater. 

Most of Auckland's water comes from dams in the Hūnua and Waitākere ranges. It is treated at four plants: Ardmore, Huia, Huia Village and Waitākere. The treatment process is:

1. Screening: water passes through screens that remove any large debris, such as leaves, branches, rubbish and dead insects.
2. Coagulation: to remove any dirt that remains, we typically add a compound known as aluminium sulphate (alum) to the water. The alum and dirt particles stick together (coagulate) into large, heavier particles called ‘flocs’.
3. Clarification: the water is pumped into settling tanks, or clarifiers, where most of the floc settles on the bottom of the tank and is removed. The clarified water is collected from the top of the tank.
4. Filtration: the water is forced through sand filters. These trap any remaining particles in the water.
5. Chlorine disinfection: chlorine is added to kill any germs (micro-organisms), such as E. coli and campylobacter, which might remain after filtration.
6. Fluoride: fluoride is added to the Auckland metropolitan water supply. Onehunga is an exception; however, this is changing mid-2024 (see note below about the fluoride directive). Learn more about fluoride in our water supplies.
7. pH balancing: the final stage is to balance the pH of the water.

Water in the Waikato River travels more than 400 kilometres through towns, past farms and industries before it reaches our treatment plant in Tuakau. Runoff from farms and industries that use the water, such as power stations, affects the quality of the water, so we use extra treatment steps such as ultra-filtration to make sure it’s safe to drink.

Our ultra-filtration process uses membrane technology: clarified water is pushed through fine membrane filters that prevent tiny micro-organisms such as giardia and cryptosporidium from passing though. This makes the Waikato treatment plant one of the most sophisticated in Australasia.

View our Waikato River water treatment process

If you live near one of our water treatment plants you should know what to do in the case of a chlorine emergency. Admore Water Treatment plant is a special case and has a higher level of safety procedures, including an annual emergency loudspeaker test.

What should I do if there’s a chlorine emergency?

In case of a chlorine incident at a water treatment plant, the local community response is to shelter-in-place. This means:

• Go indoors immediately

• Close all doors and windows

• Wait for the 'all clear' before going outside

If there’s an emergency, you’ll hear our 'shelter-in-place' message, and when it’s safe, you’ll hear our 'all clear' message.

In the case of an incident, we work closely with emergency services to coordinate the community. Follow the direction of our staff and/or emergency services.

Living near Ardmore Water Treatment Plant

Note that under legislation, the Ardmore Water Treatment Plant at 250 Creightons Road is classed as a major hazardous facility. This means there are strict safety procedures and processes, monitored by WorkSafe, and an annual emergency loudspeaker test.  More information.

The emergency loudspeaker test occurs once a year for approximately three minutes. As part of our safety planning and review process, we test the loudspeaker to check the tone and message are operating correctly and it can be heard clearly in the area surrounding the plant.

The test will sound a tone, followed by: Testing. Testing. Testing. Watercare Test. Testing. Testing. Testing. Watercare Test.” Listen to the test message.

Our labs provide water, air and solids testing for Auckland and the rest of New Zealand. Our lab is accredited by International Accreditation New Zealand to ISO 17025 (general requirements for the competence of testing and calibration laboratories). An automated computer network integrated with the labs analyses the water quality at our treatment plants 24 hours a day. Learn more.

We use pressure control valves and monitoring to adjust water pressure in small amounts at points across our network, delivering consistent water pressure levels.

Things that can impact water pressure in our pipes are:

• The geography of the area

• The length of the pipe bringing water from the nearest reservoir to your home/business

• Where you live: distance and elevation from a reservoir can affect your pressure. Properties in low areas receive higher water pressure and properties in high areas receive lower water pressure.

• Demand: water pressure is usually at its highest during the night when demand is low. When demand is high, which is typically in the morning or evening and during summer months, water pressure is at its lowest.