Melbourne's drinking-water treatment depends on the source and supply route. Protected catchments, open catchments and seawater need different treatment paths. For supply-area details, read Melbourne Water's Water Quality Annual Report 2024-25: its supply-area table sits beside a plant-by-plant treatment table. Read that financial-year snapshot alongside the newer public explanations, then ask the retailer which locality applies to the address. The technical report.
Protected catchments and added filtration
Melbourne Water's treatment overview says much of the city's water comes from protected catchments and requires disinfection. Water from open catchments has additional particle-removal stages. Coagulation gathers small particles into larger ones; clarification or flotation separates them; filtration removes more particles before disinfection. A disinfection description leaves the earlier particle-removal steps to be checked for that route. The treatment overview, updated 3 March 2026.
Protected source geography also needs a local treatment reading. The annual report describes additional membrane filtration for Healesville and Yarra Glen, and includes Yan Yean among its large filtration plants. Its account of those smaller supplies explains why the aqueduct route and the absence of a storage buffer can call for additional barriers. A broad claim about protected catchments should therefore leave room for the plant that serves the locality. The report's treatment section and tables.
Winneke and Tarago use different processes
The public overview describes Winneke at Sugarloaf Reservoir using coagulation, clarification and sand filtration. Tarago is gravity fed from its reservoir and uses coagulation, dissolved-air flotation and filtration, ultraviolet treatment and chemical additions. Flotation separates particles by floating them, whereas clarification can allow them to settle. Use the description for the relevant plant when following a supply route. The Winneke and Tarago descriptions.
Tarago's reservoir page describes a typical supply area across south-eastern suburbs, the Mornington Peninsula and Westernport towns. It also records the reservoir's reconnection to the network in 2009 after the treatment plant was completed. That area description is useful context, but it does not identify the active source blend for a particular accommodation today. Tarago's supply and history.
Desalination adds another route
Melbourne Water describes desalination as removing salt and minerals from seawater, then adding minerals back before the water enters the supply. The route enters at Berwick and continues to Cardinia Reservoir, where it mixes with catchment water; water can then transfer to Silvan. This is another reason to avoid assuming one reservoir or one treatment plant supplies a home permanently. How desalinated water enters the network.
The same page records a 2026-27 desalinated-water order announced on 7 April 2026. An order describes the planned supply for that period, not the fraction in your glass on a particular day. Keep order announcements, delivered-water records and an address-specific supply answer separate.
Ask which supply applies to your address
Melbourne Water's system overview describes interconnected reservoirs and delivery to retail water companies, which distribute water to homes and businesses. The annual report says sampling localities can receive one or more sources during the day or year. Ask the retailer or property host for the relevant locality and its dated water-quality information, and follow any current instructions for the property. The bulk and retail supply route.
Infrastructure announcements also need their dates. The Mount Evelyn project page, updated 7 July 2026, describes backup treatment for Silvan supply and an early-2027 commissioning milestone. Keep that planned facility separate from a plant already operating. The Mount Evelyn project. Our Melbourne guide provides broader travel context; this treatment explanation leaves individual tap conditions to the property's current information.
