Under Sink RO Water Filter | 6 Stage

A 6-stage under-sink reverse osmosis system — our top-tier residential RO build, adding an alkaline mineral cartridge as Stage 6 to re-mineralise the permeate water and lift pH back toward neutral. The result is RO-purified water with the mineral profile and mouthfeel of natural spring water rather than the slightly flat taste of straight RO output.

What the Alkaline Stage Adds

Reverse osmosis is highly effective at removing dissolved contaminants — but it removes beneficial minerals (calcium, magnesium, potassium) along with the bad. Pure RO permeate has very low TDS, slightly acidic pH (typically 5.5–6.5), and a flat taste many people describe as "missing something".

The alkaline cartridge in Stage 6 solves three things in one stage:

• Re-mineralisation: releases calcium and magnesium back into the water as it passes through
• pH adjustment: lifts the pH from slightly acidic toward neutral or slightly alkaline
• Taste improvement: mineral content gives the water the natural mouthfeel of spring water

For anyone who's tasted straight RO water and found it lacking, the 6-stage build is what fixes that.

Six-Stage Filtration

• Stage 1 — PP spun sediment filter (5 micron): sand, dirt, rust, particulate
• Stage 2 — Granular activated carbon (GAC): bulk chlorine reduction; protects the membrane
• Stage 3 — Carbon block (CTO): secondary chlorine and chemical polish
• Stage 4 — TFC RO membrane: purification stage at 0.0001 micron; manufacturer specification reduces up to 99% of TDS, heavy metals, arsenic, mercury, fluoride, and over 1,000 contaminants
• Stage 5 — Post-carbon polish (acid-washed coconut carbon): smooth, refined taste finish on the permeate water
• Stage 6 — Alkaline mineral cartridge: re-mineralisation and pH lift to neutralise the slight acidity of straight RO

All cartridges 10" × 2.5" standard format. 12 L pressure storage tank.

What's Included

• 6-stage RO filter system (housings + starter cartridges)
• TFC RO membrane
• 12 L pressure storage tank
• Stainless steel filter faucet
• 1/2" threaded inlet block and valve
• 2 m of 1/4" tubing
• Mounting hardware, pressure-reducing valve
• Opening spanners (10" housing + RO membrane)
• Quick-connect hose fittings
• Installation manual

Service Interval

Replace cartridges every 6–12 months; RO membrane every ~24 months. Two replacement-set options to suit your service preference:

• Standard 6-stage replacement set — value-priced cartridge set with regular carbon block
• Premium 6-stage replacement set — upgraded with coconut carbon block for chloraminated supplies (Sydney, Melbourne, Brisbane, Adelaide, Canberra)

How This Tier Compares

• 5-stage: same RO purification, no alkaline. Suits owners who like the cleaner RO taste.
• 6-stage (this product): adds alkaline. Suits owners who want spring-water mouthfeel and pH balance.