Monitoring fluoride levels at water treatment plants

We have sensors for monitoring the level of fluoride in the water at each of the four metropolitan Wellington drinking water treatment plants. These readings are taken automatically. The daily averages per plant are calculated (using an arithmetic mean method) and provided monthly to Ministry of Health.

Our aim is to maintain a steady level of fluoride in the water at treatment plants that meets the Ministry of Health fluoride target of 0.7 – 1.0ppm. This is the amount recommended by the Ministry of Health and the World Health Organisation to provide protection against tooth decay.

We also have controls in place to ensure we never supply consumers drinking water over the Maximum Acceptable Value (MAV) of 1.5ppm.

The latest data (November 2023) on the levels of fluoride in the water supplied to Wellington:

Listed below are the percentages and monthly average fluoride levels that the plants achieved for the month of November 2023.

Water Treatment Plant	Areas Supplied	Percentage met (Portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Mārua	Upper Hutt, North and West Wellington	99%	0.85
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	84.1%	0.71	Shutdown for bi-annual reservoir clean and some minor analyser issues.
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	52.4%	0.69	Server upgrades by contractors and issues with pumps.
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	98%	0.87

Listed below are the percentages and monthly average fluoride levels that the plants achieved in previous months.

October 2023

Listed below are the percentages and monthly average fluoride levels that the plants achieved for the month of October 2023.

Water Treatment Plant	Areas Supplied	Percentage met (Portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Mārua	Upper Hutt, North and West Wellington	68%	0.62	Fluoride dosing turned off for an extended period due to leaks in the transfer pumps. Repairs required.
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	49%	0.46	Health and safety risk identified, some equipment being switched out.
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	88%	0.75	Scheduled work on the pumps throughout the month.
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	90%	0.78	Health and safety risks identified, dosing was turned off until resolved.

September 2023

Listed below are the percentages and monthly average fluoride levels that the plants achieved for the month of September 2023.

Water Treatment Plant	Areas Supplied	Percentage met (Portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Marua	Upper Hutt, North and West Wellington	99%	0.85
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	98%	0.81
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	83%	0.74	Multiple pump maintenance events and planned shutdowns.
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	96%	0.83

August 2023

Listed below are the percentages and monthly average fluoride levels that the plants achieved for the month of August 2023.

Water Treatment Plant	Areas Supplied	Percentage met (Portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Mārua	Upper Hutt, North and West Wellington	99%	0.81
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	97%	0.79
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	80%	0.7	Plant shutdowns due to UV reactor, pump, dosing issues and planned works.
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	97%	0.81

July 2023

Listed below are the percentages and monthly average fluoride levels that the plants achieved for the month of July 2023.

Water Treatment Plant	Areas Supplied	Percentage met (Portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Marua	Upper Hutt, North and West Wellington	95.6%	0.83
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	96.5%	0.79
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	91.7%	0.76	Fluoride levels at the Gear Island Water Treatment Plant were under the 95% mark this month due to some operational issues with the fluoride facility.
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	97.5%	0.81

June 2023

Listed below are the percentages and monthly average fluoride levels that the plants achieved for the month of June 2023.

Water Treatment Plant	Areas Supplied	Percentage met (Portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Marua	Upper Hutt, North and West Wellington	94%	0.79	PLC maintenance
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	100%	0.79
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	94%	0.79
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	94%	0.8	Plant off on some days and some testing of high residual alarms

May 2023

Water Treatment Plant	Areas Supplied	Percentage met (Portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Marua	Upper Hutt, North and West Wellington	100%	0.8
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	100%	0.79
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	90%	0.77	Fluoride Dosing off for planned work
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	90%	0.76	Fluoride dosing off for planned replacement of instruments

April 2023

Water Treatment Plant	Areas Supplied	Percentage met (portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Marua	Upper Hutt, North and West Wellington	97%	0.77
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	94%	0.74	Fluoride levels at the Waterloo Water Treatment Plant were under the 95% mark this month due to some updates undertaken to the algorithm in the controls system at the plant.
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	80%	0.77	Fluoride levels at the Gear Island Water Treatment Plant were under the 95% mark this month we experienced some issues with the fluoride instruments in the first half of the month.
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	84%	0.71	Fluoride levels at the Wainuiomata Water Treatment Plant were under the 95% mark this month as we had some issues with the fluoride instruments and we had to commission a fluoride dosing pump.

March 2023

Water Treatment Plant	Areas Supplied	Percentage met (portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Marua	Upper Hutt, North and West Wellington	100%	0.81
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	97%	0.76
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	88%	0.80	Fluoride levels at the Gear Island Water Treatment Plant were under the 95% mark this month as we were trialling and testing new fluoride analysers (which read the fluoride levels in the drinking water).
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	81%	0.71	Fluoride levels at the Wainuiomata Water Treatment Plant were under the 95% mark this month due to planned maintenance work, which meant we had to turn off the facility while this work was underway.

February 2023

Here's the latest data (February 2023) on the levels of fluoride in the water supplied to Wellington:

Water Treatment Plant	Areas Supplied	Percentage met (portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Marua	Upper Hutt, North and West Wellington	97%	0.77
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	100%	0.78
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	93%	0.76	Fluoride levels at the Gear Island Water Treatment Plant were under the 95% mark this month as we are trialling and testing the new fluoride analysers (which read the fluoride levels in the drinking water) and replacing a pump in the fluoride facility. This required us to turn off the facility from time to time throughout the month.
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	75%	0.70	Fluoride levels at the Wainuiomata Water Treatment Plant were under the 95% mark this month as we had to turn off the water treatment plant due to wet weather events in February.

January 2023

Water Treatment Plant	Areas Supplied	Percentage met (portion of readings within Fluoride target)	Average Dose (ppm)	Comments
Te Marua	Upper Hutt, North and West Wellington	100%	0.77
Waterloo	Hutt City, CBD, Eastern-Southern Wellington (excl. Petone, Stokes Valley)	100%	0.77
Gear Island (taken at the supply main)	CBD, Eastern-Southern Wellington Only	94%	0.79	Fluoride levels at the Gear Island Water Treatment Plant were under the 95% mark this month we are trialing and testing new fluoride analysers. Fluoride analysers read the fluoride levels in the drinking water.
Wainuiomata	Wainuiomata township, Eastern-Southern Wellington	91%	0.76	Fluoride levels at the Wainuiomata Water Treatment Plant were under the 95% mark this month as we had to turn off the water treatment plant due to wet weather events in January.

Other Drinking Water Analysis

We complete additional chemical analysis of the water supply, as part of the requirements set by the Drinking Water Standards.

This analysis is performed by Eurofins, which is an independent IANZ-accredited laboratory.

You van view the annual chemical analysis here.

Data Usage Disclaimer

We aim to ensure the data published on this page is accurate and up-to-date. Wellington Water does not accept any responsibility for the use of or reliance on the data and shall not be liable to any person on any ground for any loss, damage or expense arising from such use or reliance.