Water quality and filtration

How we provide clean, safe water

We live in a world-class city, so it’s no surprise that our drinking water is among the best in the world. We protect our community by providing locally sourced, clean and safe drinking water to over 5 million people every day. How we do it takes a lot of science and dedication.

Producing drinking water

It’s our job to make sure you have access to high-quality drinking water that tastes great and is safe to drink straight from the tap.

There are lots of ways to produce safe drinking water. Most of the time, it involves a physical process (like filtering) and a chemical process (like balancing pH).

All around the world people choose methods of producing drinking water that:

  • are safe and reliable
  • are cost effective
  • achieve good quality water.

It's also important to consider the water source and tailor the process to suit it. The quality of the incoming water could be different because of:

  • the types of activities in the catchment
  • natural minerals in the water
  • weather conditions, like droughts or high rainfall
  • natural hazards, like bushfires.

In Sydney, we use modern water filtration and desalination plants. This ensures we achieve a consistent, high standard. Every drop meets the Australian Drinking Water Guidelines, which are some of the strictest in the world.

You might like to investigate how other parts of the world produce drinking water. Learn more at Water Aid.

Water filtration

Filtration steps

  1. We use fine mesh screens to remove debris, like twigs and leaves.
  2. We adjust the pH to aid the filtration process.
  3. We add a solution (coagulant) that makes the smallest particles stick together to form larger flocs. This makes it easier to filter them out.
  4. We use filters made of tightly packed beds of sand and crushed coal to trap and remove the floc. We clean our filters several times a week and continuously monitor their performance to ensure your water quality always remains high.
  5. We carefully balance the pH of the water.
  6. We add small amounts of chlorine to protect the water from harmful pathogens.

As a final step, we add small amounts of fluoride to the water as a safe and effective way of preventing dental decay. It’s not part of the filtration process, but is done under the advice of NSW Health.

Learn more about how we filter water at Orchard Hills Water Filtration Plant.

Did you know?
Both chlorine and fluoride are natural substances that can be found in water and things you eat and drink every day such as teas and seafood.
Find out about the water analysis in your area.


The desalination plant uses reverse osmosis membranes to extract freshwater from saltwater. These membranes are a physical barrier that block dissolved solids like salt, so only freshwater can pass through.

Desalinated water is excellent quality, meets the Australian Drinking Water Guidelines and is monitored by NSW Health just like all our drinking water.

Unlike rivers and dams, the amount of water in oceans isn't affected by changing rainfall.

Desalination can give us a reliable supply of drinking water. While the plant is operating, we can adjust the capacity based on our system's needs.

Learn more about Sydney Desalination Plant.

Sydney Desalination Plant at Kurnell can provide up to 15% of greater Sydney's drinking water needs.

Make a simple water filter

Using everyday items, discover what makes a good water filter and learn how Sydney's water is filtered so it's safe to drink.

Water quality monitoring and reporting

It's important that our water is safe to drink, but high quality water means much more than that.

People like their water to:

  • look clear and colourless
  • smell right
  • taste how we expect.

We have Australian Drinking Water Guidelines that tell us exactly what high quality water should be like.

The guidelines:

  • set the standards for good quality drinking water
  • outline good practices for operating a water supply system
  • help protect public health
  • tell us how drinking water should look and taste.

Did you know we do over 70 different tests to make sure your drinking water meets the guidelines?

We continuously test our water in certified laboratories and report our results to NSW Health.

We take samples from:

  • drinking water sources, including rivers and streams
  • water supply dams and storages
  • water filtration plants
  • the drinking water network
  • customers' taps.

We test the samples for a range of water quality characteristics. 

The characteristics are categorised as physical, chemical and microbial.




Total dissolved solids
Dissolved oxygen

Free chlorine
Inorganic chemicals (dissolved salts)
Organic compounds


Our Sydney Water Monitoring Services laboratory is one of the leading water testing facilities in Australia. It provides a range of biological and chemical tests. Our laboratory and field sampling teams are accredited by Australia’s National Association of Testing Authorities.

Find out more about the water analysis in your area.

Teacher resources

Make a simple water filter (182KB) – experiment

Drinking water filtration (494KB) – fact sheet

Stage 4 Science – make a simple filter lesson plan (196KB) – how can we use filtration to separate a mixture?

Stage 6 Earth and Environmental Science – make a simple filter lesson plan (207KB) – how can water be managed for use by humans and ecosystems?

Drinking water taste test (201KB) – set up a blind taste test as an experiment

Distillation practical investigation (230KB) – learn how distillation can be used to make clean water

Crystallisation practical investigation (274 KB) – see why crystallisation is important in monitoring and managing water

Make a pH indicator experiment – video

Our drinking water quality – video

Glossary – definitions of keywords and industry terms