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Buying Guide how do I choose the best Reverse Osmosis (RO) Water Filter?

This guide assumes that the reader is already familiar with what reverse osmosis is and why it is a good choice for pure water:

The first thing to decide on when buying a reverse osmosis water filter is whether you need a portable bench top system or an under sink plumbed in reverse osmosis system.

In most instances an undersink system is the better choice, the process is slow and with a plumbed in system you get a holding tank which ensures that you always have a good supply of pure water as close as your tap.

A countertop reverse osmosis system is great for those who are renting and cannot install a system. The countertop system requires the user to fill up a container of water over the period of a few hours.

Reverse Osmosis systems come at many different price points so how do I know what to look out for when I buy a system?

First thing is do not buy a reverse osmosis system purely based on price, this can result in you either buying an overpriced system which is simply not any better than a unit half the price. On the other side beware of units that are extremely cheap, remember this is an investment in your health. The following information is vital to know in order to make the right choice.

  • The most important thing to look out for is that the system is NSF 58 certified

For a home point-of-use device to claim a reduction in fluoride, it must meet National Sanitation Foundation (NSF) Standard 58 criteria for fluoride removal. Standard 58 requires that a device must achieve a 1.5 milligrams per liter (mg/L) concentration in the product water if the original concentration was 8.0 mg/L, or approximately 80 percent removal. This percentage removal may not be consistent at lower concentrations of fluoride. Check with the manufacturer of the individual product for specific product information.

  • Where is the product manufactured does it meet Australian Plumbing Standards?

Systems that are to be connected to the main supply in Australia must be AS3497 tested and Water Mark approved, this is your safe guard that the system that you install will not fail under the water pressure and conditions found in Australian homes.

  • A reverse osmosis requires a carbon filter in order for it to work effectively

The carbon filter is important as a reverse osmosis membrane will not remove volatile organic compounds, chloramines or chlorine. Make sure that the carbon cartridge that comes with your system deals with this, most important.

  • Water Waste

Reverse osmosis works by flushing contaminants to drain, some cheaper systems may end up flushing as much as 10-15 litres of water to drain for every litre of water produced. A quality system will run at a ratio of 1:1.

  • Water Filter Tap and tubing

So we have purified the water using quality cartridges and components, it is critical that all the contact points that the pure water then come into contact with are NSF approved. There is little point in purifying the water only for it to pass through a tap containing lead or plastic tubing that may contaminate the water.

  • Holding Tank

The quality of the tank that holds the pure water is critical. Again make sure that it is NSF approved and that it has a butyl bladder which ensures that it is completely safe to store pure water.

  • How many stages

The amount of stages that an RO system has is irrelevant as to the quality of water produced, we have seen 7 stage or above systems which do not get close to the purity of water produced by a high quality 4 stage RO unit.

  • Ease of Service

Modern RO systems now come with quick change cartridges which make servicing the system each year as simple as changing a light bulb. Beware of sellers claiming that their systems are quick change when in actual fact the membrane and post filters are anything but.


Questions to ask before you buy?

Where is the system manufactured?

Is the membrane NSF 58 certified?

What is the waste ratio of the system?

Is the system water mark approved?

Does the system meet (Australian Standards) AS3497?

Does the system remove chlorine, volatile organic compounds and Chloramines?

Is the Tank NSF approved?

Does the tank have a butyl bladder?

Are the tap and tubing NSF certified?

Does the system come with a pressure limiting valve?

What is the warranty supplied, what does it cover?

If you are having the system installed ask if it is installed by a licensed plumber

A reputable dealer will be able to answer all of these questions straight away, if you can find a system that meets all of the above you can then safely start comparing pricing with other companies.