Water discolouration is usually an aesthetic issue rather than a health issue. In all but the most severe cases, the particles you see are harmless, and the risk of illness from consumption is low.

Discolouration can occur in the wet or dry season. It often becomes noticeable in your white bath or basin, or as you pour yourself a glass of water. From time to time, it may cause staining of your white laundry.

The water quality problems you experience at home are usually seasonal, short-lived and you can easily fix them by flushing the taps. However, if the problem persists or is causing you concern, please let us know.

Common drinking water quality problem factsheet

What causes widespread discolouration?

If your water is yellow, brown, red or black, it may be a widespread seasonal discolouration. Other factors could also be considered, including natural events such as low rainfall and cyclones.

Discolouration could also be related to the plumbing at your home or business.

Commonly, discolouration occurs when layers of water in Darwin River Dam mix due to changes in weather.

During the wet season, deep water containing higher levels of iron and manganese mix with upper levels. This mixture then enters the water supply system.

With the first significant rains or after heavy rainfall associated with cyclones, colour may increase as dissolved organic matter originating from soils and vegetable matter enters surface reservoirs.

During this period, customers may notice an intermittent change in colour to their drinking water, and it may contain particles.

Water may appear yellowish to brownish in the initial part of the wet season and reddish to black towards the start of the dry season.

During the dry season, iron and manganese that’s settled in water pipes following the wet mobilise when flows increase.

Early in the season, irrigation water usage also increases significantly as gardens and lawns begin to dry out. Elevated water use leads to increased flows in pipes which dislodge biofilms, various materials and built-up sediments.

Biofilms are a build-up of microorganisms that form when water is in contact with a solid surface. Other types of materials found in water at this time include chemical films, scale and corrosion deposits.

Power and Water undertake a flushing program in Darwin each year to reduce the potential occurrence of discoloured water. Sometimes, the onset of discoloured water can be sudden and limited to a street or area. There may have been some activity that’s changed the rate or direction of flow in the water main supplying your home.

A significant valve or fire hydrant fault could cause a change of flow. A burst water main could also lead to sudden, high flows in pipes.

If you live on a dead-end street, it may take longer for discoloured water to clear. It may even be necessary for us to flush the mains in your street.

Other common problems

Older homes and businesses built in the 1970s or earlier may have galvanised iron pipes in their plumbing systems which have rusted.

The corrosion of metal pipes and fittings installed in household plumbing systems can cause drinking water to be brownish and contain visible particles.

Discoloured water is common first thing in the morning when there’s been no water used overnight, or if the building has been left vacant for a while. The water should run clear after flushing the tap for a couple of minutes.

Hot water systems accelerate corrosion. If the cold water is clear and the hot water is brownish or contains noticeable particles, this suggests corrosion of the hot water system.

Flushing the hot water system may help to clear out the sediment buildup in the bottom of the tank. Always be careful when working with hot water systems. Consider consulting a plumber.

What can you do?

First, try flushing the system. If water discolouration occurs in conjunction with a noticeable reduction in water pressure, the pipes may need to be replaced by a licenced plumber.

To check for corroded galvanised pipe in your plumbing system, compare water samples from a front tap near the water meter and a tap at the back of your house or in the backyard.

  • If the water from the front tap is of noticeably better quality than from a rear tap, this indicates corroded galvanised iron pipe in the plumbing system.
  • If the sample from the tap is initially discoloured and becomes clear after flushing, then all or part of the pipe before this point could be galvanised.
  • If the water doesn’t become clear, the problem is likely to be more widespread and occurring in other homes in the area.

Usually, widespread discolouration occurs for a short time. If it persists, please let us know.

Blue or green staining on white baths or basins indicates there’s copper in water. The water may have a metallic taste as well.

Household plumbing systems comprise copper pipes and copper alloy components which slowly corrode over time releasing copper.

  • The safe level for copper in drinking water is 2 mg/L. Water with a level above this should not be consumed or used for food preparation.
  • Water with copper levels between 3 mg/L and 5 mg/L can cause nausea, abdominal pain, vomiting and diarrhoea.
  • Prolonged exposure to high levels of copper over many months can cause more serious problems.
  • Some people are more susceptible than others.
  • Water with a copper level of 2 mg/L or higher is usually cloudy or has a blue or green tinge and blue or green particles.

What can you do?

  • Establish a process of flushing your plumbing system first thing each morning before using water for drinking or food preparation.
    • Run an open tap into a white container like a bucket or an ice cream container.
    • Flush the tap at full flow, collect at least two to three litres of water and then let the water stand for a few seconds.
    • If the water appears blue or green, or if there are blue or green particles in the container, then the copper level may be close to or above 2 mg/L.
    • If this is the case, empty the container and flush the tap into the bucket for a further 30 seconds.
    • Check, and if the water is clear, the water is acceptable for consumption. If the water is not clear, repeat the flushing process until you observe clear water.
  • Prevent staining by repair leaking taps to stop constant dripping on surfaces.

If you’re still concerned, contact us.

Cloudy drinking water is usually caused by the presence of harmless, tiny air bubbles in the water.

Air is introduced into drinking water in many ways:

  • Sudden filling of a glass by quickly opening a tap
  • Taps fitted with aerators introduce air into the water stream to reduce splashing and to provide uniform flow. Sometimes, the aerator can become blocked. To avoid this, clean your aerator regularly.
  • Water coming from hot water systems can also be aerated and appear cloudy.
  • If air is sputtering from taps, this could be from recent repair works on your plumbing system or for a burst water main.
  • Air can become trapped in pipes when they are refilled with water. We usually flush repaired mains to release trapped air. All trapped air is released from taps as you use water.
  • Another cause of cloudy water could be mild corrosion of copper pipes in your plumbing system.

What can you do?

If you notice cloudy water:

  • fill a clean, clear glass with cold water and let it sit on a bench.
  • if the water starts to clear at the bottom of the glass, the colouring has been caused by air bubbles and is safe to drink.

If you believe air bubbles haven't caused the issue, please let us know.

Before the onset of the wet season in the Top End, elevated levels of algae can form in large surface storages like Darwin River Reservoir.

These algae can result in compounds forming in the water which can change water taste and odour.

What can you do?

  • To reduce the earthy or musty taste or odour, flush your tap for several minutes.
  • Then, collect the fresher water into a clean container for future drinking or cooking purposes.
  • Adding a few drops of lemon juice or a slice of lemon can also help improve the taste.

If the issue persists, please let us know.

Many locations in the Northern Territory rely on groundwater supplies that are characterised by hard water. Medical research has established that hard water is safe to drink.

Above a certain level of hardness, water can cause scale formation on hot water systems, pipes, fittings and domestic appliances reducing or blocking water flow. We’re currently trialling a Calgon chemical dosing system. The system doesn’t reduce hardness or remove the existing scale build-up, but it’s expected to decrease further scale build-up.

As surface water is softer, where possible, we blend groundwater with surface water from a reservoir or river to improve drinking water quality.

What can you do?

  • Hard water reacts chemically with soap. So, use more soap to form a lather.
  • Use a good rinsing agent in your dishwasher, or a vinegar rinse for spots on drinking glasses, windows and shower screens.

Chlorine is added to drinking water to kill harmful microorganisms and ensure it’s safe to drink.

A minimum free chlorine residual of 0.2 mg/L is needed to control bacterial contamination in most places. However, a minimum of 0.5 mg/L is required to control Naegleria fowleri which has been found in Northern Territory drinking water

The Australian Drinking Water Guidelines recommend a maximum limit of 5 mg/L for free chlorine. As chlorine levels decay through the water supply system, our systems contain higher levels closer to the point where dosing takes place. However, levels are at least 0.6mg/L throughout the distribution system, including customers’ taps.

What can you do?

Some people are sensitive to chlorine odour and can detect levels as low as 0.05 mg/L.

  • If you’re sensitive to chlorine odour, collect water in a clean container and let it sit overnight for future drinking or cooking purposes.
  • Adding a few drops of lemon juice or a slice of lemon can also help improve the taste.

Customers in Darwin, Palmerston and rural areas on reticulated water may occasionally notice small white particles in drinking water.

The particles are likely to be Botryococcus Braunii, a species of green algae found in Darwin River Reservoir.

After entering the water supply system, these algae die in response to chlorination and light deprivation but can be seen as bleached floating or suspended particles.

What can you do?

You can read our Drinking Water Quality Report here.

If you have questions, please contact us.

What can you do?

  • If you’re concerned about the water quality at your home or business, ask your neighbour if they’re experiencing the same issue. If they are, you’ll know it isn’t a problem you need to call a plumber to fix.
  • To flush discoloured water at home, run at least two taps for several minutes, flush the toilet a couple of times or turn on your garden irrigation system.
  • Don’t use hot water if the cold water is discoloured, as this will fill your hot water system with discoloured water.
  • If you’re washing clothes, it’s better to stop the cycle with the machine full and wait until clean water is available to finish. Emptying the machine and allowing it to go into a spin cycle can cause permanent staining. Add a stain remover or dishwashing detergent to assist with removing stains that may be present. (Some research indicates that staining is less of a problem in front-loading washing machines.)
  • As discoloured water isn’t appealing to drink, let the tap run for a few minutes to improve the water’s colour. Current scientific evidence indicated the risk of illness from discoloured drinking water is considered to be low.

Usually, discolouration occurs for a short time. If it persists please inform us.

Let us know