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How to buy the best Reverse Osmosis System

Buying the best reverse osmosis water filter system can be tricky, if you do not know the appropriate logistics behind it. In fact, this area is something we get asked about often, so we decided to put together this unbiased guide to help make the buying decision easier.

If you want more information on how reverse osmosis water filters work follow this link.

Where to start?


When buying a reverse osmosis (RO) water filter, the most important factor to consider is whether or not the system is ANSI/NSF 58 approved. This standard is concerned with the performance of Reverse Osmosis drinking water systems and checks for material safety, structural integrity and accurate product literature. The performance claims include the following contaminants:

Arsenic Reduction

Asbestos Reduction

Barium Reduction

Cadmium Reduction

Copper Reduction

Cyst Reduction

Fluoride Reduction

Hexavalent Chromium Reduction


Lead Reduction

Mercury Reduction

Nitrate/Nitrite Reduction

Radium 226/228 Reduction

Selenium Reduction

TDS Reduction

Trivalent Chromium Reduction

Turbidity Reduction

VOC Reduction

NSF 58 requires that RO systems to be tested and certified for the reduction of total dissolved solids (TDS). These systems are tested for 7 days and include measurement of the systems daily purified water output, wastage and efficiency. Other contaminant claims can be tested at the manufacturer’s request. All testing of RO systems is performed after removal of any pre and post filters, so performance is based on the RO membrane.

Two RO units must be used for all testing and both units must pass to meet the requirements of the standard.

All certified product and system manufactures are inspected during the course of initial certification to verify manufacturing consistency. Once certified, unannounced annual inspections are performed. These inspections include review of inventory records, parts and material verification, product documentation reports, manufacturing walk through, quality assurance documentation review and the use of marking on products and literature. Any problems or variances must then be corrected in a timely manner.

Product retesting is then required at five year intervals for continued certification. Any changes made to products after certification need to be authorised by NSF with re-evaluation or further testing required in many cases.

All of our reverse osmosis membranes have NSF 58 certification.

Waste Ratio

When buying a RO water filter system, it’s also important to consider its waste ratio. All ro systems work in the same way, the pure water is forced through a semi permeable membrane which will only allow water and an extremely small percentage of contaminants to pass through, the contaminants are rinsed away to waste. The waste ratio depends on a number of factors including pressure, temperature and the quality of the membrane. A lot of systems run at a water to waste ratio of 1:6, we have developed ro systems which will produce around 400 litres a day with a waste ratio of 1:1 which will result in considerable water savings over the lifetime of the water filter. The ideal water pressure to run a reverse osmosis is 450 KPA, they can run as low as 250 KPA and the maximum pressure is around 850 KPA. All plumbed in ro systems should be fitted with a pressure limiting valve.

WATER MARK AS:3497       

In relation to systems that are permanently connected to the town water supply please ensure that

they are tested and approved to Australian Water Mark level 1.

Failure to meet this requirement could lead to failures and leaks.

It is also a requirement of the Australian plumbing code.


Ultimately, the reverse osmosis water filter system you choose to buy should meet appropriate Water Mark Level 1 standards and the membrane must be NSF 58 approved. It’s also essential to consider the waste ratio, so you do not waste a lot of water flushed to drain.