The Ministry of Health produce a Register of Community Drinking-Water Supplies in New Zealand.
There are two gradings used, with the first letter (capital) representing the source and treatment grading, while the second letter (lower case) grades the water in the distribution zone itself. The following is a simplified explanation of the grading system.
The Source and Treatment Grading (Capital Letter)
Assessment based on source and treatment factors:
A1 Completely satisfactory, negligible level of risk, demonstrably high quality
A Completely satisfactory, very low level of risk
B Satisfactory, low level of risk
C Marginal, moderate level of risk, may be acceptable in some smaller communities
D Unsatisfactory, high level of risk
E Completely unsatisfactory, very high level of risk
Distribution Zone Grading (Lowercase Letter)
Assessment based on reticulation condition, management, and actual water quality:
a Completely satisfactory, negligible level of risk, demonstrably high quality
b Satisfactory, low level of risk
c Marginal, moderate level of risk, may be acceptable in some small communities
d Unsatisfactory, high level of risk
e Completely unsatisfactory, very high level of risk
u Ungraded
From the 2004 Edition of the Register our Water Supplies are graded as follows:
Central Urban - Ba
Eastern Area - Bd
Ngongotaha - Ed
Mamaku - Ca
Mihi - Db
Hamurana - Dd
Okareka - Bb
Rotoiti - Ud
Rotoma - Ca
Kaharoa - Dd
Reporoa - Db
Note: The fact that the Rotorua District Council does not chlorinate some of it's supplies fulltime is predominately the reason for the lower gradings (d) in the distribution gradings. Ngongotaha has a low grading in the source because of past contaminations.
(To view the results of the water analysis, click the PDF icon)
(48KB) Water Analysis
Rotorua District Council attempts to ensure that all supplies comply with the current Drinking Water Standards of NZ.
This is measured firstly, by all permanently chlorinated supplies achieving compliance with the microbiological criteria of DWSNZ 2000. Secondly, the unchlorinated supplies achieving compliance at the source with the monitoring requirements of DWSNZ 2000. Finally to initiate the prescribed response to microbiological contamination events as per the DWSNZ 2000.
In the Rotorua District the water comes from aquifers which produce extremely clean water and very little treatment is required. Most supplies can be disinfected using chlorine treatment when it is required. Fulltime disinfection by chlorine in the District is carried out in the following water supplies:
- Central
- Mamaku
- Rotoma
- Reporoa
The Rotorua District Council does not fluoridate any of their supplies.
The following is a list of common water problems along with the probable cause and recommended solutions:
- Sign - Yellow to rusty brown water, stains on washing.
Cause - Rusting iron pipes at home or sediment in the water supply.
Solution - Rusting iron pipes. 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. These pipes need to be replaced with plastic or copper pipes. Sediment in the supply system. If the water does not clear after turning the tap on full, the problem is not in your pipes and there is little that you can do. Small particles settle at some places in the water system. Dirty water results if this sediment is disturbed in some way. This is a particular problem for dead end streets. You should contact the Rotorua District Council or Castlecorp. They will arrange to have the supply mains cleaned and flushed.
- Sign - Small particles in the water.
Cause - Rusting iron pipes at home or sediment in the supply.
Solution - Rusting iron pipes. 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. These pipes need to be replaced with plastic or copper pipes.
Sediment in the supply system. If the water does not clear after turning the tap on full, the problem is not in your pipes and there is little that you can do. Small particles settle at some places in the water system. Dirty water results if this sediment is disturbed in some way. This is a particular problem for dead end streets. You should contact the Rotorua District Council or Castlecorp. They will arrange to have the supply mains cleaned and flushed.
- Sign - Brackish (salty), metallic or stale taste.
Cause - Rusting Iron pipes at home.
Rusting iron pipes. 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. These pipes need to be replaced with plastic or copper pipes.
- Sign - Green or blue water, green stains on plumbing.
Cause - Corroding (being eaten away) copper pipes at home.
Solution - This is a difficult problem to solve. Ask Rotorua District Council to test your water.
- Sign - White, cloudy or milky water.
Cause - Air in the water.
Solution - 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. However the Rotorua District Council can flush the the mains to get rid of the air if the problem continues.
- Sign - Poor lathering of soap.
Cause - Calcium in the water.
Solution - Calcium has been leached from the new cement lined pipes. This often improves with time. The Rotorua District Council only use concrete lined pipes in special situations.
- Sign - Blackened aluminium cooking utensils and white deposits on stainless steel sinks.
Cause - Calcium deposits.
Solution - Calcium has been leached from the new cement lined pipes. This often improves with time. The Rotorua District Council only use concrete lined pipes in special situations.
- Sign - Slight smell of chlorine.
Cause - Chlorine in the water.
Solution - Chlorine is added to disinfect the water. Sometimes the smell of chlorine is noticeable but this is not harmful and should not continue for any length of time.