Te putu, te tiaki me te arotūruki wai
Water collection, treatment and monitoring
We supply water from a mix of rivers, dams and groundwater. We carefully treat, test and monitor the water to make sure you have a steady supply of safe and clean water for drinking and other uses.
Where does your water come from?
Most of Auckland’s water comes from our dams in the Hūnua and Waitākere ranges, the Waikato River and groundwater. In the week finishing 13 July 2025, the proportion of water taken from each source to supply the metropolitan Auckland area was:
- Dams = 77.56%
- Waikato River = 21.38%
Where Auckland’s water comes from depends on water storage levels, forecast rainfall, treatment plant capacity and the cost of pumping water to our reservoirs.
How do we treat your water?
We treat all the water we supply to you to make sure it’s safe to drink. When treating your water, we screen it to remove dirt and debris, filter it to remove smaller particles, and then disinfect it to kill germs.
The exact treatment process depends on where the water comes from, as some sources are cleaner than others. We have 17 treatment plants around Auckland to cover all the water sources and over 9,000kms of pipes to get the water to you.
You can learn more about our treatment processes and living near our treatment plants below.
Treating water from different sourcesOur 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.
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.
Treating water from our dams 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:
- Screening: water passes through screens that remove any large debris, such as leaves, branches, rubbish and dead insects.
- 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’.
- 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.
- Filtration: the water is forced through sand filters. These trap any remaining particles in the water.
- Chlorine disinfection: chlorine is added to kill any germs (micro-organisms), such as E. coli and campylobacter, which might remain after filtration.
- 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.
- pH balancing: the final stage is to balance the pH of the water.
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:
- Screening: water passes through screens that remove any large debris, such as leaves, branches, rubbish and dead insects.
- 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’.
- 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.
- Filtration: the water is forced through sand filters. These trap any remaining particles in the water.
- Chlorine disinfection: chlorine is added to kill any germs (micro-organisms), such as E. coli and campylobacter, which might remain after filtration.
- 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.
- pH balancing: the final stage is to balance the pH of the water.
Treating water from the Waikato River 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.
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.
Living near our water treatment plants 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.
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.
Watercare labs 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.
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.
Monitoring and testing water
Testing is a vital part of ensuring that the drinking water we provide is safe and always meets New Zealand Drinking Water Standards. Our labs continuously monitor the water quality from our treatment plants, and we also carry out location-based testing.
Every day our technicians carry out an average of 366 tests on water samples from points across the network, from collection at the source to coming out of your tap.
During collection, we check water for harmful contaminants, such as algae, faecal coliforms, giardia and cryptosporidium. This testing ensures we take quick and appropriate action if unusual results show up, like restricting use of that source.
We also test the water leaving our water treatment plants to check chemical parameters and look for any signs of micro-organisms in the water. We then monitor the pH, water clarity and residual chlorine.
Keeping you informed about water quality
In the unlikely event that the water we supply becomes unsafe to drink, we or the Medical Officer of Health will alert you immediately, do further testing to identify the cause of the quality issue, and take one of the following actions:
- Temporarily close the supply
- Vary the treatment process
- Isolate affected assets/areas
- Supply water from other supply points or sources
- Use a tanker to provide water
If you see any issues with the quality of water we supply, such as a change in clarity, taste or smell, please report a fault. We’ll investigate and, if needed, test your water to find out the cause.
Pressure management
It’s important to make sure the pressure in water pipes across Auckland is suitable for everyday use, as high pressure can burst a pipe or cause a leak.
What are the benefits of pressure management?
- Water pipes last longer.
- The water supply is more dependable and there are fewer interruptions.
- It reduces the need for excavation work to repair broken mains.
How does water pressure management work?We use pressure control valves and monitoring to adjust water pressure in small amounts at points across our network, delivering consistent water pressure levels.
We use pressure control valves and monitoring to adjust water pressure in small amounts at points across our network, delivering consistent water pressure levels.
What impacts the pressure in water pipes? 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.
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.
Frequently asked questions about water collection, treatment and monitoring
Frequently asked questions about water collection, treatment and monitoring
Related pages
Related pages
Learn more about water hardness, how it affects your water and what you can choose to do.
Learn about our wastewater services and how we keep Auckland’s environment healthy and clean.
As Auckland grows we need to consider the future of our water supply, services and new water solutions.