What actually gets into a tank, what a laboratory test looks for, and why the honest answer is never a general one.
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Water quality and filtration
Filters are sold as one thing and are actually five different things. What you need depends entirely on what is in your water: which you have to measure, not assume.
A filter only removes what it is designed to remove
"Water filter" covers products that do completely unrelated jobs. Sediment filters remove particles and protect everything downstream. Activated carbon targets taste, odour and chlorine. Reverse osmosis removes dissolved solids, which is a much bigger job, wastes some water and strips minerals. UV disinfects but removes nothing physical. Softeners address hardness, scale, and are not a purification device at all.
Choosing between them without knowing what is in your water is guesswork. On mains supply, your water authority publishes water quality data for your area and that is the honest starting point. On tank, bore or spring water, the only real answer is a laboratory test by a NATA-accredited lab.
We do not tell anyone their water is safe to drink. Not tank water, not bore water, not filtered water. That is a laboratory result read against the Australian Drinking Water Guidelines, and it is specific to your property, your roof, your catchment and your season. A website that tells you otherwise is guessing with someone else's health.
Hard water is a plumbing problem before it is a drinking problem. Scale shortens the life of a hot water system, blocks aerators and shower roses, and reduces heat transfer. If your kettle scales quickly and your shower rose blocks every few months, that is what you are looking at. And maintenance matters more for you than for most.
Water quality guides
What RO removes that carbon cannot, the three inherent drawbacks, and why most mains households are solving a problem they do not have.
Carbon block, reverse osmosis and ultrafiltration are sold under the same label. What each removes, and why installing one is licensed plumbing.
Fitted to the mains line, a whole-house filter protects every outlet and the hot water system from sediment and chlorine. What it doesn't do: soften water or remove dissolved solids.
Hardness isn't a health issue on Australian mains water. It's scale that shortens the life of hot water systems, taps and shower roses.
Groundwater is untreated and differs from block to block. What is in it and what to ask a laboratory.
Good for taste and chlorine, no help with salts or hardness. Change the cartridge on schedule.
Rain, bore, dam and recycled water are not drinking water by default. How to tell which tap is which.
Untreated surface water: fine for stock and the garden, a poor bet for the kitchen tap.
Check the cold tap, ask the neighbours, then decide whether it is the mains or your pipes.
A water report, a strip kit or a soap test: three ways to learn how hard your water is.
Clear does not mean safe. What a laboratory checks and why you should not guess.
A glass of water and two minutes tell you whether it is air or something else.
Which taps, hot or cold, and when: three checks that point to the cause.
Vinegar or citric acid for taps, showerheads and kettles, and what to leave alone.
Why suppliers dose the water, and the cheap fixes for the taste before you buy a filter.
Where the orange and brown marks come from, how to clean them safely, and what to test.
How a softener works, when it is worth the money, and what to ask before you buy.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NHMRC. Australian Drinking Water Guidelines
- Sydney Water. Water supply, wastewater and stormwater services