The following table shows the mean values of chemical analysis of the water supply from the Wainuiomata Water Treatment Plant, for the year ended 30 June 2018, compared with the maximum allowable value (MAV) or guideline value (GV) for each element as set out in the Drinking Water Standards New Zealand (DWSNZ).
Notes: (A) MAV denotes the maximum acceptable value to comply with the Drinking-water Standards. (B) GV denotes the maximum guideline value in the Drinking Water Standards.
Parameter DWSNZ MAV (A) / GV (B) No of samples Median value Max value Alkalinity - total g CaCO3/m³ - 13 29 36 Aluminium - total g/m³ 0.1 (B) 14 0.031 0.047 Arsenic - total g/m³ 0.01 (A) 2 <0.002 <0.002 Boron - total g/m³ 1.4 (A) 2 <0.05 <0.05 Cadmium - total g/m³ 0.004 (A) 2 <0.001 <0.001 Calcium hardness g CaCO3/m³ 200 (B) 11 29.455 33.000 Chloride g/m³ 250 (B) 1 22.2 22.2 Chromium total g/m³ 0.05 (A) 2 <0.001 <0.001 Conductivity at 25°C mS/m - 1 15.6 15.6 Copper - total g/m³ 2 (A) 13 <0.013 <0.013 Cyanide g/m³ 0.6 (A) 2 <0.005 <0.005 Fluoride g/m³ 1.5 (A) 103 0.49 0.91 Hydrogen sulphide g/m³ 0.05 (B) 1 <0.05 <0.05 Iron - total g/m³ 0.2 (B) 13 0.028 0.043 Lead - total g/m³ 0.01 (A) 2 <0.001 <0.001 Manganese - total g/m³ 0.04 (A) 13 <0.013 <0.013 Mercury - total g/m³ 0.007 (A) 2 <0.001 <0.001 Nickel - total g/m³ 0.08 (A) 2 <0.001 <0.001 Nitrate - nitrogen g/m³ 50 (A) 2 0.035 0.05 pH 7.0-8.5 (B) 14 7.507 7.7 Selenium - total g/m³ 0.01 (A) 2 <0.005 <0.005 Silica g/m³ - 2 13.2 13.9 Sulphate g/m³ 250 (B) 1 5.6 5.6 Total dissolved solids g/m³ 1000 (B) 1 77 77 Zinc - total g/m³ 1.5 (B) 13 <0.013 <0.013