Warnbro Water Hardness & Quality Report (2026)

Warnbro's drinking water is supplied by the Water Corporation via the Integrated Water Supply Scheme (IWSS), incorporating Gnangara Mound groundwater and a proportionally higher Kwinana Seawater Desalination Plant contribution for the City of Rockingham LGA outer southern Perth distribution in Western Australia. Water hardness in Warnbro is measured at 108.5 mg/L — classified as slightly hard — within the Australian Drinking Water Guidelines (ADWG) aesthetic guideline of 200 mg/L published by NHMRC. Warnbro — a residential suburb in the outer southern Perth City of Rockingham LGA adjacent to Safety Bay and Shoalwater Bay, known for the Warnbro residential estate, the Safety Bay coastal reserve on the Shoalwater Islands Marine Park shoreline, and the outer southern Perth coastal community south of the Rockingham Beach tourist precinct — receives a notably softer supply than many outer Perth sub-zones, reflecting the proportionally higher desalination fraction from the nearby Kwinana plant.

Warnbro's relatively soft supply reflects a proportionally higher Kwinana Seawater Desalination Plant fraction in the outer southern Rockingham IWSS distribution blend. The Kwinana Desalination Plant (producing very soft, low-mineralisation desalinated supply) is located at Kwinana Beach, immediately adjacent to the Rockingham LGA — providing a proportionally higher low-mineralisation desalinated supply fraction to the nearby Rockingham outer southern distribution. At 108.5 mg/L and TDS 241.3 mg/L, Warnbro is considerably softer than many outer Perth IWSS sub-zones (Hamilton Hill 209 mg/L, Waikiki 234.5 mg/L), reflecting the geographic proximity to the Kwinana desalination source.

Warnbro residents can expect moderate limescale on taps and in kettles — descaling every two to three months is typically adequate. Hot water systems benefit from periodic inspection. The very low lead reading (0.001 mg/L) is excellent. Under WA water restrictions, garden irrigation is limited to two days per week. The Water Corporation provides water quality information at watercorporation.com.au, with all ADWG health standards met. Warnbro's Shoalwater Bay coastal community and the outer southern Perth residential estate benefit from supply meeting all ADWG standards.