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Water quality

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    Our water is clean and safe to drink, without needing further treatment.

    To ensure we provide the world's best water, we follow the water health standards and guidelines set out in state and federal regulations:

    For more information on these quality requirements, read our Annual Water Quality Report. 

    Monitoring and reporting

    GWW supplies high-quality, treated water from local reservoirs and Melbourne Water’s catchments.

    Our water quality is the product of rigorous monitoring and reporting. This includes checking our treatment plants daily and taking samples from reservoirs, water filtration plants, storage tanks, pump stations and customer taps.

    We test our water daily to make sure it meets a range of quality standards. Reservoirs are also tested regularly for the presence of PFAS (per and polyfluoroalkyl substances). 

    We employ independent testing laboratories to make sure your water is the best it can be. These independent labs are accredited by the National Association of Testing Authorities.

    Sometimes your water may look, smell or taste different than usual. Usually, these changes are harmless and your water will soon return to normal.

    If you do experience an issue with your drinking water, contact us on 13 44 99.

    PFAS and your drinking water

    PFAS (per and polyfluoroalkyl substances) are human-made substances found in many industrial and everyday products. These include firefighting foams, pesticides, fertilisers, carpet, paint, frying pans, make-up, sunscreen and clothes.

    Known as ‘forever chemicals’, they are of concern because they can persist for a long time, both in the environment and in humans.

    PFAS chemicals are not added to drinking water but tiny amounts are commonly detected in groundwater, surface water and soils worldwide.

    For most people, the level of exposure to PFAS from drinking water is likely to be small.

    Monitoring for PFAS

    GWW tests its reservoirs for PFAS chemicals each month. It’s part of our water quality testing and monitoring program. Melbourne Water also conducts regular monitoring for PFAS chemicals on its open water supply catchments.

    Testing follows the Australian Drinking Water Guidelines set by the independent National Health and Medical Research Council (NHMRC).

    The Australian Drinking Water Guidelines specify safe limits for three PFAS: PFOA (Perfluorooctanoic acid), PFOS (Perfluorooctane sulfonic acid) and PFHxS (Perfluorohexane sulfonic acid).

    These limits currently state:

    • Less than 0.56 micrograms per litre for PFOA
    • Less than 0.07 micrograms per litre for the sum of PFOS and PFHxS combined.

    For comparison, 1 microgram per litre is equivalent to one part per billion.

    These safe levels are determined through the NHMRC by the Australian Government.

    Since GWW’s testing for PFAS chemicals started in 2023, all our results are below the limits set out by the current guidelines.

    Results from recent monitoring by Melbourne Water also show concentrations of PFAS below those set out in the current guidelines.

    Proposed changes to PFAS limits

    New draft guideline limits for PFAS have been released by the NHMRC for public consultation. If endorsed, the new guideline limits will be finalised in April 2025.

    GWW welcomes the draft update and is currently reviewing the proposed changes. Results from recent monitoring by GWW and Melbourne Water are still below the proposed limits.

    Learn more

     

    Understanding your water

    Chlorine taste or odour

    Tap water can sometimes have a chlorine taste or odour, but it is safe to drink.

    If you are sensitive to the taste or odour of chlorine, fill a container with water and put it in the fridge. The chlorine will dissipate from the water over a few hours.

    The Australian Drinking Water Guidelines recommend a maximum of 5 milligrams of chlorine per litre of water. Levels less than 1.2 milligrams per litre are normally measured in our water distribution system.

    The level of chlorine can be higher if you live close to where it is added to the water supply. Seasonal or daily changes in water demand and flow can also affect chlorine levels.

    Why is chlorine added to drinking water?

    Chlorine is a proven health measure that has been used globally for more than 100 years to disinfect water supplies.

    Small amounts of chlorine are added to our drinking water supply to kill waterborne, disease-causing micro-organisms and ensure our water is safe for drinking.

    The level of chlorine is strictly controlled and is continuously monitored at different points throughout our supply network.

    Milky-white water

    Sometimes the colour of your tap water may have a milky-white, cloudy appearance.

    White water is known as aerated water. It consists of very small air bubbles that can be caused by trapped air in the distribution mains following maintenance works. It could also be due to a build-up of air in your hot water system.

    To check if milky-white tap water is safe to drink, follow these steps:

    1. Stand a glass of the cloudy water on a bench and observe it for a minute or two.
    2. If the water starts clearing from the bottom upwards, the cause of the cloudiness is aerated water. This water is perfectly safe to drink. There is no need to take any further action, though you may wish to wait until the water is cleared before drinking it.
    3. If the water does not clear, or it doesn't clear from the bottom upwards, call us on 13 44 99.

    Brown-coloured water

    Sometimes your tap water may have a light yellow to brown or muddy colour. If you use your washing machine, you may find brown stains on clothes after washing a load.

    Brown water can be the result of:

    • a build-up of natural sediments in the water pipes
    • significant water flow changes in Greater Western Water’s mains, which disturb the sediments and discolour the water (for example, after a burst water main)
    • the corrosion of galvanised-iron water pipes, if you live in an older property. The rust particles in the water make it appear brown.

    To check if the water is safe to drink, follow these steps:

    1. Turn on a tap at the front of your property for up to 2 minutes until it runs clear. Then run a tap on at the back of your property and let it flush out the brown water.
    2. If the water clears temporarily, but then becomes brown again later, it is likely to be caused by corroding galvanised-iron pipes. You may want to contact your local plumber to fix this problem.
    3. If the water does not clear, call us on 13 44 99.

    Blue-green water

    Your drinking water may have a blue-green tinge, with possibly blue-green particles in the water and a bitter or metallic taste to it.

    Blue-green water happens because of elevated levels of copper in the water. This copper comes from the internal corrosion of copper water pipes and fittings.

    Blue-green water should not be consumed, as it can result in vomiting and adverse health effects.

    You may require a plumber to fix this problem. For more information, call us on 13 44 99.

    Water filters

    Melbourne’s water supply is largely unfiltered, resulting in small, naturally occurring quantities of invisible, fine or suspended particles.

    Though they can be incorrectly perceived as poor-quality drinking water, these particles are harmless.

    Over time, the particles will accumulate on water filters, causing blockages and restricting water flow.

    The rate of particle accumulation on water filters varies, depending on:

    • filter pore size
    • particle content of the local supply
    • seasonal variations in microscopic, harmless algal populations that are naturally present in Melbourne’s reservoirs.

    All water filters that trap and accumulate particles will eventually restrict water flow and become blocked.

    For more information on premature filter blockage, call us on 13 44 99.

    Using a water filter

    Given our compliance with drinking water standards and quality guidelines, we don't believe there is a need to use domestic water filters.

    Often, individual filter units have little effect on improving the quality of a household's water supply. For instance, filters may claim to remove substances that in fact aren't even present to any significant degree in our water supply. In some cases, filter units can actually cause a deterioration of water quality.

    Find out more

    Annual Water Quality Report