City of Port Phillip Water Hardness & Quality Report (2026)

The City of Port Phillip's drinking water is supplied by South East Water, with bulk water managed by Melbourne Water from the Thomson Reservoir, Upper Yarra Reservoir, and O'Shannassy Catchment in the protected Yarra Ranges, Victoria. Water hardness in Port Phillip is measured at 37 mg/L — classified as soft — well within the Australian Drinking Water Guidelines (ADWG) aesthetic guideline of 200 mg/L published by NHMRC. Port Phillip shares the Melbourne Water supply system, one of Australia's largest and most carefully managed catchment networks.

Port Phillip's soft supply reflects the shared Melbourne catchment geology. The Thomson and Upper Yarra catchments sit atop ancient Devonian granite and Silurian metamorphic rocks of the Yarra Ranges — formations that resist chemical weathering and contribute very little dissolved calcium or magnesium. The closed, protected nature of Melbourne Water's catchments, maintained since 1891, ensures consistent, low-mineral supply throughout the year regardless of seasonal variation.

Port Phillip residents — in densely settled inner suburbs such as St Kilda, South Melbourne, and Albert Park — experience minimal limescale on tap fittings and in kettles, with descaling only an occasional task. Hot water systems accumulate very little scale over their operational life, reducing maintenance costs particularly in the area's many heritage terrace homes. Some residents in pre-1970s properties install a whole-house filter as a precaution, as the soft, slightly acidic supply can be mildly corrosive to lead solder joints in older internal plumbing — a standard consideration noted in the ADWG for older Melbourne housing stock.