Water is generally drinkable in Australia and is usually signposted if it is not safe.
According to the CDC tap water is generally safe for consumption.
According to the Numbeo water drinkability and accessibility index, tap water has a score of 86.45 / 100 (100 being best).
Numbeo considers this score to be "Very high"
1 adult could save about 1110$ per year in Australia by drinking tap water instead of buying bottled water.
๐ณ Drinking tap water would also help with reducing your plastic footprint and improve environmental pollution.
Like in most countries, water quality and accessibility differs from location to location, therefore it's the best to check the information available on that place.