Sediment and rusty water from the tap
Brown, orange or gritty water at a Melbourne tap is usually sediment lifted out of the water main by a burst, a repair, a hydrant being used or a change in flow direction nearby, and it normally clears within a few hours to a day.
What to do first, today
Run a cold outside tap or the laundry tap for a few minutes and see if it clears, and check your retailer's outage page before you buy anything.
Avoid running hot taps while the water is discoloured, because that draws the sediment into your hot water system rather than flushing it straight out. Hold off on washing light coloured laundry until it runs clear, since sediment stains fabric. Greater Western Water, South East Water and Yarra Valley Water all publish current outage and works information for their area, and a quick check often explains what is happening before you spend anything. If it clears and never comes back, no purchase is required.
When it is your own pipes instead
If discoloured water only comes out of the hot tap, the problem is usually the hot water system rather than the mains.
Old galvanised pipe inside a house can shed rust internally as it ages, and a corroding hot water tank does the same from the inside out. A pattern worth noticing is discolouration only on the first draw of the morning, which points to sediment settling overnight inside the tank or the pipe rather than anything arriving from the street. A main line filter sits before your internal plumbing, at the point water enters the house, so it protects what comes after it but does not reach back into a fault that already exists downstream of itself. We would rather say that plainly than sell a filter as a fix for a problem it cannot solve.
What sediment does if it keeps happening
Repeated sediment gets into the hot water system, the washing machine and dishwasher inlet screens, tap aerators and toilet cistern valves, and it is those fixtures rather than your health that it costs you.
Inlet screens and aerators clog and need cleaning more often, cistern valves can start running or sticking, and a hot water system accumulates sediment at the bottom of the tank over years, which reduces its effective capacity. None of this is a health question. It is wear on fittings and appliances that are otherwise fine.
What stops it
Sediment is stopped at the main line, before the water reaches anything in the house, by a coarse filter followed by a finer one.
A 5-micron washable sediment filter goes first, sized to catch the rust and grit that a mains event can push through without clogging immediately. A 5-micron filter follows it, catching what the coarser stage lets past. Running the finer filter last means it lasts longer, because most of the load is already removed by the coarser stage ahead of it, and it is why the order of the stages matters rather than being arbitrary. Any sediment filter needs its cartridge changed on schedule, typically every twelve months, or it becomes the thing holding the sediment rather than the thing removing it.
What it costs
A three-stage whole-house filter installed by a licensed plumber is $2,990 fixed with Every Tap, including the cartridges fitted at install.
What a whole-house water filter costs in Melbourne sets out the full published range. Fresh Tap, $2,990 has the full specification.