Water Quality

Water supply grading

The Ministry of Health produces the Register of Community Drinking-Water Supplies in New Zealand, which uses two grading's.
Source and treatment grading
Based on source and treatment factors
Distribution zone grading
Based on reticulation condition, management, and actual water quality
A1 Completely satisfactory, negligible level of risk, demonstrably high quality   

A Completely satisfactory, very low level of risk A Completely satisfactory, negligible level of risk,   demonstrably high quality 
B Satisfactory, low level of risk B Satisfactory, low level of risk 
C Marginal, moderate level of risk, may be acceptable in some smaller communities C Marginal, moderate level of risk, may be acceptable in some small communities 
D Unsatisfactory, high level of risk D Unsatisfactory, high level of risk
E Completely unsatisfactory, very high level of risk E Completely unsatisfactory, very high level of risk 
U Ungraded U Ungraded 

The table below shows the previous and current grades:



New 2017


E a

A a


E c

A a


D a

A a


D a

A a


D a

E a


D b

A b


E a

A a


E b

A a


E c

A a


E a

A a


Complying with standards

Council works to ensure that all supplies comply with the Drinking Water Standards of New Zealand (DWSNZ 2005) revised (2008).


In the Rotorua District our water is extremely clean and requires little treatment. Water Supplies are disinfected using chlorine treatment. Council adds a small amount of chlorine (0.4mg/l) to all supplies.

UV treatment plants have been installed on all supplies except Mamaku to comply with the DWSNZ 2005 (Revised 2008).


We do not fluoridate any of the Rotorua District’s water supplies.

Water issues

Problem: Yellow to rusty brown water, stains on washing Small particles in the water or stale taste                   Cause:     Rusting iron pipes at home or sediment in the water supply

Turn a tap on full for a couple of minutes. If the water turns clear, the brown colour is probably due to rusting iron pipes at home. The pipes may need to be replaced with plastic or copper pipes.

If the water does not clear or still tastes stale after turning the tap on full, the problem is not in your pipes. Small particles settle at some places in the water system. Dirty water results if this sediment is disturbed in some way. Contact Council and we will arrange to have the supply mains cleaned and flushed.

Problem:  Metallic taste or smell
Cause:     Corroding pipes or fitting (plumbosolvency)

Plumbosolvency is when minute traces of the metals in your pipework and fittings leach into the water when it is not being used. Turn a tap on full for a couple of minutes to flush the pipework.

Problem:   Green or blue water, green stains on plumbing
Cause:      Corroding copper pipes at home
Problem:  White, cloudy or milky water
Cause:      Air in the water        

If you hold up a glass up to the light, there will be tiny bubbles moving up from the bottom of the glass. This is not harmful. Council can flush the mains to get rid of the air if the problem continues. Calcium has been leached from cement-lined pipes. This often improves with time.

Problem:  Slight smell of chlorine
Cause:     Chlorine in the water
Council adds chlorine to disinfect the water. This is not harmful and the smell will not continue for long.

Water Hardness


Plumbosolvent Water- Notice to Consumers

Many natural New Zealand waters tend to be “soft” with moderate to low levels of alkalinity and pH. These properties can give the water the potential to leach metals from taps and other plumbing fittings when water stands for several hours, for example overnight,  (ie. are “plumbosolvent”)

To ensure that any risk from higher levels of metals is avoided, the Drinking Water Standards of New Zealand requires that Drinking Water suppliers pass on to consumers the following message from the Ministry of Health.

"Although the health risk is small, the Ministry of Health recommends that you flush a mugful of water from the tap each morning before use to remove any metals that may have dissolved from the plumbing fittings."

Page reviewed: 03 Jul 2019 10:13am