Mandurah Water Hardness & Quality Report (2026)

Mandurah's drinking water is supplied by the Water Corporation via the Integrated Water Supply Scheme (IWSS), drawing on the Harvey Dam on the Harvey River, Wellington Dam on the Collie River, Gnangara Mound limestone groundwater, and the Kwinana Desalination Plant south of Perth, Western Australia. Water hardness in Mandurah is measured at 200 mg/L — classified as hard and at the Australian Drinking Water Guidelines (ADWG) aesthetic guideline threshold of 200 mg/L published by NHMRC. Supply hardness varies with the seasonal blend ratio between desalinated, reservoir, and groundwater sources.

Mandurah's hardness reflects the dual nature of its supply. The Harvey and Wellington reservoir catchments drain through the Darling Plateau granite and gneiss, which contribute modest mineral loads, while the Gnangara Mound groundwater component percolates through Tamala Limestone and the Superficial formation of the Swan Coastal Plain — a porous limestone system where calcium carbonate dissolves readily into groundwater. The blended IWSS supply at Mandurah's southern Perth location typically produces hardness at or near the ADWG aesthetic threshold.

Mandurah residents deal with significant limescale accumulation on taps, shower screens, and in kettles — weekly to fortnightly descaling is common in many households. Solar hot water systems, popular in WA for their energy savings in the sunny coastal climate, are susceptible to scale build-up inside the tank and collector tubes; annual servicing is strongly recommended. Evaporative coolers used in summer accumulate mineral scale on evaporative pads, which should be replaced each season. Under WA water restrictions, garden irrigation is limited to two days per week during summer, making appliance care and indoor water efficiency a practical everyday priority.