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PSI-021-4S 4 Stage Reverse Osmosis Under Sink Unit Standard Model



  • USA Made Filters
  • Optional Reminerliser
  • 3 Yr Warranty

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Regular price $510.00
Regular price $510.00
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Reverse Osmosis Undersink 4-Stage System

Enjoy ultra-clean water from a dedicated faucet with our efficient 4-stage reverse osmosis (RO) system. Built for reliability, it achieves a water-waste ratio of ~1.25:1 — markedly better than most standard RO units.

Why Choose This System?

  • Compact under-sink installation — neat footprint with a dedicated faucet for easy access.
  • Advanced 4-stage filtration — high-performance, U.S.-made filters for excellent taste and clarity.
  • Genuine DOW FilmTec membrane — ~200 L/day at 50 psi (350 kPa), up to ~300 L/day at 87 psi for faster refills.
  • No electricity required — operates on water pressure with auto shut-off & integrated check valves.
  • Low waste ratio (~1.25:1) — more water-efficient than many standard systems.
  • Certified & compliant — components to Australian Standards + NSF/ANSI 42/53/58.
  • Optional alkaliser — restores minerals and balances pH for smoother taste.

How It Works: 4-Stage Filtration

  • Stage 1 — 1-micron sediment (U.S.) removes dirt, sand and particulates.
  • Stage 2 — Omnipure coconut carbon block (U.S.) reduces chlorine, chemicals and odours (rated ~37,000 L chlorine removal).
  • Stage 3 — DOW FilmTec RO membrane (U.S.) removes ~96–98% fluoride, heavy metals and dissolved impurities (TFC).
  • Stage 4 — Omnipure coconut carbon post-filter (U.S.) polishes taste and removes residual organics.
  • Optional — Alkaliser with crushed marble/limestone to re-mineralise and neutralise acidity.

System Specifications & Features

  • Premium components — 550 kPa pressure-limiting valve with dual check valves (WaterMark AS1357-2).
  • Installation — typical install 30–60 minutes for a confident handyman.
  • Minimum pressure — 40 psi (280 kPa); ideal: ≥50 psi (350 kPa).
  • Main unit size — 42 cm (H) × 35 cm (W) × 14 cm (D).

Connection Types

  • ½″ Flick-Mixer Braided Line — most common in modern kitchens. Fit the supplied adapter with the rubber washer, then re-attach the braided hose to the adapter’s ½″ male thread.
  • ¾″ Dishwasher Adapter — use the dishwasher cold-water outlet where no dishwasher is installed.
  • ½″ Tee Olive Fitting (Copper) — typical for older homes with copper pipes to separate taps. Cut 45–50 mm from the ½″ copper line, deburr, install the tee, then proceed with the standard PLV/tubing steps.

Storage Tank Options

  • Standard — 9 L stainless steel tank (NSF certified).
  • Alternative sizes:
    • 4.2 L — 33 cm (H) × 20.5 cm ⌀
    • 9 L — 39 cm (H) × 24 cm ⌀
    • 12 L — 39 cm (H) × 27.5 cm ⌀

Faucet Options

Bundle & save: upgrading your faucet with the system is cheaper than buying it later.

Browse Faucet Range, then select your choice from the Faucet Option dropdown above.

Replacement Cartridges & Maintenance

Warranty

This system is backed by a 5-year warranty for peace of mind. Built with premium components and tested for durability and performance. Covers defects in materials and workmanship under normal use — see full warranty terms for details.

Customer Reviews

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Customer Reviews

Based on 6 reviews
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C
Chiang Chun Jee
Loving it!

The water taste so good, i dont think i can drink normal tap now.

P
Peter
Clear fresh water

The price was good and the documentation was clear and complete. The filtered water is great too.

v
vicki cashion

Beautiful sweet water from the tap 😃 I used to spend so much on boxed water. This is awesome and essential if clean water is up there as one of your priorities

F
Fiona Grant
Water with no aftertaste

Loving my new water filter, the water has no aftertaste and I find I’m drinking more water which is great. Service was great, so helpful and arrived quickly

J
Janice Voon
Quality, value, pre-built

I think this could the best quality vs price out there in Australia. Thank you for providing this service / these products