What is Reverse Osmosis?

Reverse Osmosis (RO) is the purest form water can be filtered to. RO systems remove around 98% of all contaminants in stages. Depending on the system, water is pushed through 2 to 3 pre-filters, a membrane and possibly a DI resin or remineralising filter, depending on its application. Typically it needs an optimum pressure of 80-90 PSI – so it may also include or require a separate booster pump should you not have the required pressure for it to operate correctly.

How does it work?

RO works by forcing water through a semi-permeable membrane that filters molecules down to 0.0001 microns (by comparison, a strand of human hair is 0.8 microns!). That’s fine enough to essentially remove all contaminants in the water, including hormones, fluoride and pesticides. In fact, people who drink it usually opt for a remineralisation filter to put back some of the good nutrients such as magnesium, calcium and potassium (and make it taste better!).

With a RO system, when the water is forced through the membrane under pressure, only the H2O molecules are allowed to pass through and the remaining water is rejected to the waste line. Around three-quarters of the water is rejected and the remaining quarter is pure, filtered water.

What can Reverse Osmosis systems remove?

  • Sodium
  • Lead
  • Sulfate
  • Nitrate
  • Phosphorous
  • Chloride
  • Arsenic
  • Calcium
  • Magnesium
  • Hormones
  • Copper
  • Fluoride
  • Chromium
  • Radium
  • Potassium

Pumped or unpumped system?

Reverse Osmosis works by putting water under high pressure. It needs a minimal operating pressure of 40PSI (2.75BAR) and an optimal operating pressure of 80PSI (5.5BAR). Anything below 40PSI will make the system inoperable and so a booster pump would be required. Booster pumps operate on a minimum of 29PSI (2BAR) and, depending on membrane capacity, can boost pressure up to 100PSI.

We strongly recommend checking your water pressure before you buy a Reverse Osmosis System, as adding a booster pump separately post-purchase can be costly compared to the initial price of a pumped RO system.

What are the different Reverse Osmosis stages?

4 Stage Reverse Osmosis System

Our most compact drinking water RO system, this is perfect for those who have limited space underneath their sink. It’s also our least expensive unit, and while it performs just as well as our bigger units the 4-stage system only has two pre-filters as opposed to three, and it’s not currently available as a pumped unit.

5 Stage Reverse Osmosis System

This is our mid-range unit and has both pumped and unpumped options. The 5-stage system includes an additional GAC carbon pre-filter, which reduces stress on the existing carbon block for de-chlorination. The 5-stage unit is preferable if you’re going to use the system for more than just domestic drinking water.

6 Stage Reverse Osmosis System

The 6-stage is our top of the range and most popular system. It’s available in pumped and unpumped versions, and the additional stage includes a re-mineralising filter to add essential minerals such as Calcium, Magnesium, Sodium, Potassium and more. These essential minerals are extracted during the reverse osmosis process, so it’s important to add them back into the water for health reasons.


We actually get a lot of nutrition from water, but the RO process is so thorough it removes essential minerals such as Calcium, Magnesium, Sodium and Potassium along with harmful contaminants. Our remineralising filter adds these essential elements back into the water just before it’s dispensed from the tap.


What can I do with my waste RO water?

With RO, there is around 3 to 4 times more waste water than there is pure. Most of the time, the waste water will go into a bucket and/or be disposed of down a drain. The waste water is actually highly concentrated in some minerals, which can be very good for plant life – so it’s perfect for watering your garden!