Well I've been living in Melbourne for a long time, had various darkrooms for a long time, worked in a commercial/industrial photo lab for a shortish time and found the best situation sort of depends upon exactly where in Melbourne you live.
I run an inline industrial filter that filters all incoming water into the darkroom, had this one for about 20 years and it was very secondhand when it came out of a B&W darkroom in the city in the early eighties.
It does collect bits and pieces of small solids and I change the replaceable inner filter regularly. Every now and then the filter picks up quite a lot of crap, other times it goes for a couple of years without picking up much at all.
Plus All of the developing systems we had in all of the various factories ran filters on every film and/or paper developer machine.
We probably had around 100 odd processors, I know for sure we had around 45 DuPont deep tank roller transport film processors in the Little Lonsdale St., Carlton and Collingwood graphic houses. They used filters quite a fair bit, but the Moorabbin factory, which had a smaller amount of processors, probably about 15, used virtually none. This was in the seventies and eighties when we had film and other stuff delivered by the semi trailer load and unloaded it with fork lifts on a weekly basis.
Generally speaking Melbourne water is very good, plus it is a soft water. My guess is that that is about to change once the desalination plant comes online.
I would be putting an inline water filter in, especially if you are in the inner suburbs. The street that runs along the railway line at East Richmond Station (Lesney) was sewered in 1896 and piped water was apparently connected in 1895 in anticipation of the sewerage connection. My Grandmother lived in a house in that street and remembered the sewerage going through and her father paid quite a bit of extra money to have the stables at the rear, connected to the sewerage system. You haven't lived, until you've seen a dunny designed for a load of horse manure, size counts!
Now I know that those main pipes in that street were altered, but not changed in the twenties when the railway line was dug down, prior to that the railway ran at ground level. The water in that street has never been the same since, at least according to my grandparents and I did agree with them as that water always had some cloudiness about it and when left to settle, one could sometimes see some very small solids, sometimes.
One of my friends who develops film and lives in Richmond, reckons that some streets are alright, others are a bit sus.
Having also been a personal friend (through photography) of someone who was number three in the structure of the old Melbourne Metropolitan Board of Works, some areas were positively pristine, others less so. Since the water works have been privatised, I have less faith in the long term replacement of superstructure, (shouldn't that be understructure?) and figure that certain areas of the city will be a bit dodgy.
Your call, but I'm going to buck the trend and suggest that a water filter may be a cheap long term investment.
Gary, I agree with you about the water situation in Adelaide. I have one of my sisters-in-law whose husband lives with total renal failure, and has done so for about 8-9 years now. He has discussed the water problems he has endured whilst travelling to various places in Europe. He lives in Germany and does self dialysis, on a trip he was contemplating to Australia, he was warned about drinking water inland, and especially Adelaide and anything south of Mildura.