Frankston Water Hardness & Quality Report (2026)

Frankston's drinking water is supplied by South East Water as water retailer, with bulk supply from Melbourne Water drawn from the Thomson Reservoir and Upper Yarra Reservoir catchments in the Yarra Ranges, Victoria. Water hardness in Frankston is measured at 89 mg/L — classified as slightly hard — within the Australian Drinking Water Guidelines (ADWG) aesthetic guideline of 200 mg/L published by NHMRC. Frankston, as the gateway to the Mornington Peninsula at the southern end of Melbourne's south-eastern metropolitan rail and road corridor, receives Melbourne Water's supply through the extended south-eastern distribution network, which serves Frankston and the adjacent Peninsula communities.

Frankston's elevated hardness relative to inner Melbourne (41.5 mg/L) reflects the supply characteristics of the extended south-eastern distribution network. The Yarra Ranges source catchments on Devonian granite produce soft base supply, but the extended pipeline pathway from the Thomson Reservoir through the south-east metropolitan corridor to Frankston — one of Melbourne's longer distribution arms — and the characteristics of the coastal distribution zone, including potential blending contributions, produce measurably harder supply at the outer suburban Frankston tap compared to the inner CBD.

Frankston residents see occasional moderate limescale deposits on taps and in kettles — descaling every two to three months is typical. Hot water systems benefit from an annual inspection, particularly given the coastal climate. The elevated lead reading (0.004 mg/L) warrants briefly running the cold tap before use in older established homes in Frankston's heritage residential precincts near the bay. South East Water provides water quality information at southeastwater.com.au, with all ADWG health standards consistently met throughout the Frankston supply zone.