Water supply – taste and odour issues

​​If you've noticed a change in the taste and odour of your residential water supply, this is likely to be caused by an increase in levels of algae in the water supply.

Natural algae levels generally increase in the summer months with the combination of the low flowing stream and warm temperatures. Sometimes this can affect the taste and odour of your water. The water supply is still safe to drink and complies with the New Zealand Drinking Water Standards

It is recommended that residents chill their water prior to drinking to help reduce the taste and odour.

Frequently asked questions

What is being done to make sure the water is safe to drink?

Our water supply is tested weekly to ensure it is meeting the New Zealand Drinking Water Standards. Tests include checking for the presence of any E. coli and for pH, turbidity and chlorine residual concentrations. During the summer months, when the algae levels are known to naturally increase, testing frequency is increased and the water is tested for the presence of any algae.

Council’s water quality testing is verified by an independent, IANZ-accredited, Ministry of Health approved laboratory. Other agencies such as Waikato Regional Council also monitor water quality for the presence of any algae. 

Is the water safe to drink with this unpleasant flavour?

Yes, it is completely safe to drink and complies with all New Zealand Drinking Water Standards.

Some algae result in an earthy flavour which can be detected even at very low concentrations. Although this may present an unpleasant odour and taste, the water is safe to drink. Chilling the water before drinking it reduces taste and odour issues.

If you are on a public water system, your drinking water is protected by Council to address possible contaminants, including blue-green algae and associated taste and odour issues. Water supplies owned and managed by Council are required to treat, disinfect, and manage drinking water for their customers. If water supply contaminants are detected above levels established to protect human health, you would be notified by Council and provided instructions. If there was a potential health risk, Council would advise and take immediate steps to remove the risk.

What is Council doing to fix the problem?

Council will continue to regularly monitor the water quality and keep the public informed of any significant developments.

We are also working on long term solutions to try and reduce the algae blooms.​ The change in taste and odour is a result of the increase in algae in the storage dam, due to higher temperatures and low levels of water in the stream.

To fix this, Council would need to install a dedicated treatment system which would cost $3.5m. Council decided against this as the $25m Parallel Road connection project will mitigate the issue of taste and odour significantly.​ Thi​s project is being progressed at present with the expectation to have it in service in 2021.

Where does Te Awamutu and Pirongia’s water supply come from?

Te Awamutu and Pirongia’s water comes from the Mangauika Stream on Mount Pirongia. The water is diverted from the Mangauika Stream into a settling pond, then into a storage reservoir, prior to treatment at the Te Tahi Treatment Plant.

What is algae?

Algae is a naturally caused organism which is found in fresh water. 

Blue-green algae (scientifically known as cyanobacteria) are microscopic organisms that are naturally present in lakes and streams. Under certain conditions, blue-green algae can become abundant in warm, shallow, undisturbed, nutrient-rich surface waters that receive a lot of sunlight, such as a storage reservoir.

An effect of algae in water can result in musty or earthy taste and odours.

What happens when algae levels increase in the water?

If the algae levels are causing taste and odour issues, Council follows a Algae Response Plan, which states a number of actions:

  • Begin algae monitoring in the treated water  as well as the source water 
  • Increase the amount of tests taken to monitor the water supply
  • Continue visual daily checks of the source water
  • Flush the raw water reservoir
  • Keep public informed
  • Make changes to our operational processes. For example, usually Council takes water from the upper stream which goes through settling ponds, then the storage reservoir, then the treatment plant. However when staff notice differences in algae levels, we bypass the settling ponds, and use the lower stream intake which goes direct to the treatment plant.

Feeling unwell?​​

The flavour caused by algae is unpleasant but not dangerous and not connected to adverse health effects. Council-supplied water is rigorously tested and meets all requirements of the New Zealand Drinking Water Standards and will not make you sick. If you or a family member is experiencing an upset stomach, we would always recommend contacting your doctor for advice.   ​
Page reviewed: 31 Jan 2018 11:32am