- What it does: Filters your kitchen cold tap (or a dedicated filtered-water tap) for drinking and cooking
- Installed cost: $300–$850 for a quality system including licensed plumber installation
- What it removes: Chlorine, chloramines, sediment, taste and odour — and with the right cartridge, some heavy metals
- What it doesn't remove: Fluoride, PFAS — you need reverse osmosis for those
- Requires: Licensed plumber, WaterMark certified product
- Ongoing cost: $80–$180/year for cartridge replacement
How under-sink filters work
An under-sink water filter sits inside your kitchen cabinet and connects to your cold water supply line. Water flows through one or more filter cartridges before reaching either your existing cold tap (via a diverter valve) or a separate dedicated filtered-water tap installed in your benchtop.
Most Australian under-sink systems use carbon block filtration — a solid carbon medium with a very small pore size (typically 0.5–1 micron) that traps sediment, chlorine, chloramines, and organic compounds. Quality carbon block filters produce noticeably better-tasting water than most alternatives at a much lower cost than reverse osmosis.
A benchtop filter attaches to your existing tap and filters as you pour — no plumbing required. An under-sink filter is plumbed permanently under the cabinet and delivers filtered water through your tap continuously. Under-sink filters have higher flow rates, cleaner aesthetics (hidden away), and generally better filtration performance. The trade-off is the need for a licensed plumber to install.
Under-sink filter types
Single-stage carbon block
One filter housing with a single high-quality carbon block cartridge. Removes chlorine, chloramines, sediment, and taste/odour. Simple, affordable, effective for most town mains water. Installed cost: $250–$500. Cartridge: $30–$60, replace every 6–12 months. Best for: most Australian households on town water who primarily want taste improvement.
Twin or triple stage
Multiple filter housings in series — typically sediment pre-filter → carbon block → carbon polishing filter. Better performance, longer cartridge life, broader contaminant removal. Installed cost: $400–$750. Cartridges: $80–$160/year. Best for: higher sediment water, households wanting broader contaminant coverage, those upgrading from single stage.
Inline inline filter (behind mixer tap)
A single compact cartridge installed on the cold water line feeding your existing mixer tap — no separate filter tap needed. Simplest and cheapest plumbed solution. Limited filter life (low flow rate). Installed cost: $200–$400. Cartridge: $25–$50, replace every 3–6 months. Best for: tight budgets, simple upgrades, where a separate tap isn't practical.
What under-sink filters remove
| Contaminant | Standard Carbon Block | Notes |
|---|---|---|
| Chlorine | 95–99% | Primary reason most Australians install filters |
| Chloramines | 80–95% | Requires catalytic carbon or specific cartridge for SEQ water |
| Sediment / rust | 95–99% | Depending on micron rating of cartridge |
| Taste & odour | Excellent | Most noticeable improvement for homeowners |
| Some heavy metals (lead, copper) | 50–90% | Only with specific lead-reduction cartridge |
| Fluoride | 0–5% | NOT removed by carbon — need RO for fluoride |
| PFAS | Variable | Carbon helps but NOT sufficient for serious PFAS concerns — use RO |
| Bacteria / viruses | 0% | NOT removed — use UV or RO for biological contamination |
Installation: what to expect
Choosing a tap option
You can either: (a) use a diverter on your existing mixer tap cold feed — cheaper but reduces cold water flow slightly; or (b) install a dedicated filtered-water tap in your benchtop — cleaner look, full flow, but requires drilling through the bench ($100–$250 extra for stone benchtops). Most homeowners opt for the dedicated tap if benchtop space allows.
What the plumber does
Shuts off water supply → connects a T-piece or diverter to your cold water line under the sink → mounts the filter housing → runs tube to the tap → installs tap if required → restores water and pressure tests. Most jobs take 1–2 hours. Always ask for a Certificate of Compliance on completion.
WaterMark compliance
The filter unit, tap, and all fittings must be WaterMark certified — this is Australian law. Ask any supplier for the WaterMark licence number before purchasing. Some cheap imported filters sold online are not certified. A licensed plumber will refuse to install an uncertified product and doing so would void your home insurance.
What it costs in Australia
| Component | Cost |
|---|---|
| Filter unit (single stage, quality brand) | $100–$250 |
| Filter unit (twin/triple stage) | $200–$400 |
| Dedicated filtered-water tap | $80–$250 |
| Plumber installation (1–2 hrs) | $180–$400 |
| Stone benchtop drilling (if required) | $100–$250 |
| Total — single stage, existing hole | $280–$650 |
| Total — twin stage, stone benchtop drilling | $480–$900 |
| Annual cartridge replacement | $80–$180/yr |
The physical assembly — mounting the housing, inserting cartridges — is DIY-friendly. The plumbing connection to your mains water supply must be done by a licensed plumber in Australia. This is a legal requirement, not a suggestion. A practical approach: purchase the filter unit yourself and have the plumber do only the connection work, saving assembly labour. All plumbing must comply with Australian Standards and the plumber should issue a Certificate of Compliance.
Most quality filters have a pressure gauge or change indicator. In the absence of one: when your filtered water starts tasting like unfiltered tap water again, the cartridge is spent. As a schedule: replace every 6 months in high-use households or areas with high sediment; every 12 months in average-use households. Never run a carbon filter past its service life — a depleted carbon cartridge can become a bacterial breeding ground.