Mernda Water Hardness & Quality Report (2026)

Mernda residents receive their water primarily from South East Water, which sources bulk supply from Melbourne Water. The main inputs are surface water from Sugarloaf Reservoir, fed by the Thomson River, and desalinated seawater from the Victorian Desalination Plant at Wonthaggi. Minor groundwater from aquifers in the Port Phillip and Westernport region also contributes. This blended supply, serving a vast population including Mernda's growing numbers, originates from the Thomson River catchment in the Victorian Alps. The water is treated at facilities like the Winneke Water Treatment Plant before reaching homes.

The geological makeup beneath Mernda consists of Quaternary alluvial sediments and Tertiary basalts resting on Cretaceous sandstones of the Gippsland Basin. These non-carbonate rock types, including Ordovician sandstones and mudstones in the upper catchment and Quaternary basalts and alluvium in the lower basin, release very little calcium and magnesium into the water. This geological characteristic, common to Victoria's surface waters, results in a naturally soft water profile low in dissolved minerals, a trait further enhanced by desalinated water and limited groundwater from the Otway Basin.

Because Mernda's water is soft, you'll notice less limescale buildup in appliances like kettles and dishwashers, and soap will lather up easily, potentially reducing the amount of detergent you need. While this means you likely won't need a water softener, exceptionally soft water can sometimes lead to minor corrosion in plumbing, especially if the pH is on the lower side. South East Water ensures the water meets stringent Australian Drinking Water Guidelines, using chloramine for disinfection and typically maintaining a pH between 7.5 and 8.5. Annual reports confirm compliance for lead and copper, and no PFAS have been detected in recent tests.