- Benchtop filter: $50–$400 unit only — no installation cost, DIY
- Under-sink filter: $300–$800 fully installed (unit + plumber)
- Reverse osmosis (under-sink): $800–$2,000 fully installed
- Whole house system: $1,300–$4,500 fully installed
- Annual cartridge costs: $80–$430/year depending on system
- Savings vs bottled water (family of 4): $800–$2,500/year
Complete cost breakdown by system type
The gap between "unit price" and "installed price" is the most common source of cost surprises in water filter projects. A $400 filter unit may cost $700–$900 installed once a licensed plumber is involved. A $800 reverse osmosis unit may cost $1,100–$1,600 installed. Always compare fully installed quotes — not unit prices alone.
| System Type | Unit Cost | Installation | Total Installed | Annual Maintenance |
|---|---|---|---|---|
| Benchtop / gravity filter | $50–$400 | $0 (DIY) | $50–$400 | $30–$80 (cartridges) |
| Under-sink single stage | $100–$300 | $150–$400 | $300–$700 | $80–$150 |
| Under-sink twin/triple stage | $250–$500 | $200–$350 | $450–$850 | $100–$200 |
| Reverse osmosis (5–8 stage) | $500–$1,000 | $300–$600 | $800–$1,600 | $150–$300 |
| Whole house (2-stage carbon) | $400–$800 | $500–$1,000 | $900–$1,800 | $200–$300 |
| Whole house (3-stage + UV) | $800–$1,800 | $600–$1,200 | $1,400–$3,000 | $250–$430 |
| Whole house (premium / PFAS) | $1,500–$3,000 | $800–$1,500 | $2,300–$4,500 | $300–$500 |
What drives installation cost
Location of installation
Under-sink installations in an existing kitchen with accessible plumbing: straightforward, 1–2 hours of plumbing labour. Whole house installations where the main pipe runs under a concrete slab or in a difficult-access location can require jackhammering or extended pipe runs — adding $300–$1,000 to the installation cost. Always get a plumber to assess the access situation before quoting.
New tap or existing tap
Under-sink and RO systems typically use a dedicated filtered-water tap on the benchtop. Drilling through stone, granite, or thick engineered stone benchtops requires specialist drill bits and care — add $100–$250 for this. If your benchtop already has an unused hole (e.g., from a previous soap dispenser), installation is simpler.
Number of filtration stages
More stages = more cartridges = higher ongoing maintenance cost, but potentially broader contaminant removal. A 3-stage under-sink system (sediment → carbon block → carbon polisher) handles most taste and basic contaminants. A 7-stage RO with remineralisation adds significant performance for fluoride, heavy metals, and PFAS at a higher unit and maintenance cost.
State and city location
Plumbing labour rates vary significantly. Sydney and Melbourne: $120–$180/hour. Brisbane and Perth: $100–$160/hour. Adelaide and regional areas: $90–$140/hour. Total installation time for a standard under-sink RO: 1.5–2.5 hours. Whole house: 3–6 hours depending on access and pipe layout.
Ongoing running costs — what to budget annually
Replace every 6–12 months. Quality branded cartridges essential for performance.
Pre-filters every 6–12 months, post-filter annually, membrane every 2–3 years averaged.
Sediment pre-filter every 3–6 months, carbon block every 6–12 months.
A Melbourne family of four spending $40/week on bottled water spends $2,080/year. A fully installed 7-stage RO system at $1,100 with $200/year maintenance costs $1,100 in year one, $200 every subsequent year. Payback period: under 8 months. 10-year comparison: bottled water costs $20,800; RO system costs $2,900. The financial case is overwhelming for regular bottled water buyers.
Hidden costs people miss
- Benchtop drilling: If your stone benchtop needs a new hole for a filtered-water tap, budget $100–$250 for specialist drilling — this is often not included in basic installation quotes.
- Draining the RO waste line: RO systems produce "reject water" — typically 3–4 litres of waste per litre of filtered water. This waste line needs to drain somewhere accessible (usually the under-sink drain). In some kitchen configurations this requires additional pipe work.
- Pressure booster pump (low pressure properties): RO membranes need minimum 40–60 PSI water pressure to function properly. Properties with low mains pressure (common in older suburbs and some rural areas) need a booster pump — add $200–$400.
- Non-standard benchtop penetrations: Granite, concrete, and ultra-compact surfaces require diamond drill bits and slow, careful drilling. Some installers charge extra; confirm before booking.
Frequently asked questions: costs
Unit-only prices are typically 40–80% lower than fully installed costs. Additionally, some cheap imported units are not WaterMark certified — making them illegal to connect to Australian plumbing. The total cost of a filter system includes the unit, licensed plumber installation, a new tap (if required), any benchtop drilling, and connection materials. Always compare installed prices, not unit prices.
Benchtop and gravity filters: yes, completely DIY. Under-sink filters and RO systems: the unit itself can sometimes be assembled DIY, but the plumbing connection must be made by a licensed plumber in Australia. Whole house systems almost always require a licensed plumber for the mains connection. Some homeowners assemble the unit and have a plumber do just the connection — this can save $100–$200 in assembly labour but the plumber will still charge for their time.
Manufacturer timelines are guidelines based on average flow rates. High-usage households may need to replace more frequently. The practical check: taste the water — if it starts to taste like tap water again, the cartridge is spent. Most quality systems have a filter change indicator. Never skip cartridge changes on an RO membrane — a depleted pre-filter allows contaminants to reach and damage the membrane, which costs $100–$300 to replace.