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Reverse Osmosis

ClEAR Choice water knowledge base

learn about reverse osmosis

We have put together a comprehensive knowledge base regarding the most frequent questions that we receive such as what is the best reverse osmosis filter or do RO water filters remove fluoride. If there are any questions that you cannot find here please feel free to contact us and we will answer your questions as soon as is practicable.

RO not shutting off

What to do when a reverse osmosis system continually runs to drain There are many under-sink reverse osmosis units on the market, however they all share common characteristics. Here is a quick run down on the basic operation which will help you identify what the issue...

Compare our Undersink Reverse Osmosis Systems

Reverse Osmosis  There's nothing quite like the taste of pure water as close as your tap. Now, you can avoid buying costly water bottles and the hassle of bringing them to your home. Below is a simple guide on the difference between our undersink reverse osmosis...

Which Reverse Osmosis

Reverse Osmosis Buying Guide There's nothing quite like the taste of pure water as close as your tap. Now, you can avoid buying costly water bottles and the hassle of bringing them to your home. Below is a simple guide on what you need to look for when shopping for a...


Frequently Asked Questions

Do reverse osmosis systems remove everything from the water?

The reverse osmosis membrane (if NSF 58 Certified) will remove a wide variety of impurities from the water the list below is just a few of the main contaminants that are desirable to remove from the tap water in Australia:

Copper – 99% reduction

Fluoride – 97.7%

Lead – 99.3%

What a membrane will not remove:


The membranes that are commonly used however are not chlorine resistant and that is why further stages are required before the membrane, a good quality carbon block will remove over 99% of chlorine from the water.


Many herbicides and pesticides are actually molecularly smaller than water. For this reason, they tend to pass freely through the pores of the semi-permeable membranes used in reverse osmosis. Pesticides are some of the most dangerous chemicals that should not be in drinking water. Thankfully again a a good quality carbon block will remove herbicides and pesticides from the water.

Dow Filmtec membrane treatment rates

more info dow filmtec


I heard that ro water has no minerals and is bad for you?

A reverse osmosis membrane is not selective, that is it will remove everything from the water including minerals.

There are some crazy headlines around the internet such as drinking pure water will result in death, it is interesting to note that almost all of the headlines are from water filtration companies or affiliates. Unfortunately we live in a world where some companies will grab on to a dramatic headline that suits their particular argument and helps to make a sale.

A classic example of this is an article that most people who are against drinking demineralised water will quote almost all the time without fail. The usual build up to the link is something like this ….The World Health Organization (WHO) also published a study on drinking water showing evidence of various health risks associated with drinking demineralised water.

The link is to an article from Frantisek Kozisek (an isolated report available through the WHO website) which states among other things that Sufficient evidence is now available to confirm the health consequences from drinking water deficient in calcium or magnesium”.

Here are the facts:

  • No public health organization with authority over the drinking water quality anywhere in the world has enacted or even proposed a minimum requirement for total dissolved minerals in drinking water.
  • The human body’s own control mechanism (homeostasis) regulates the mineral content of the body fluids and the discharge of different types of ions from the body of normal health individuals drinking water with low or high mineral content.
  • Several types of scientific literature searches have found no harmful effects to the human body attributable to the consumption of low TDS water.
  • Review of the Soviet report has shown that the scientific methods used are questionable and the conclusions are either vague or unsupported by the data.

Read more on reverse osmosis water and health effects here

what should i look for when buying a reverse osmosis system?

The reverse osmosis water filter system you choose to buy should meet appropriate Water Mark Level 1 standards for Australian conditions 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.

How many stages should a reverse osmosis system have?

As few as possible – the more stages the more expense in maintenance.

A sediment filter in cities such as Melbourne is a must have whereas in Sydney you may get away without using a sediment filter

A pre carbon filter is necessary as the membrane is not chlorine resistant and also will not remove herbicides and pesticides

A post carbon filter is also necessary to provide a better tasting water after the RO process

A mineralising filter can be added but is not critical

Summary if you live in an are with a low sediment load a 3 stage RO may be siuitable, however a sediment filter is inexpensive and we recommend using a 4 stage system, anything over 5 stages and you need to ask exactly why the extra cartridges are required


Questions from our customers

Here are a list of just some of the questions we have been asked over the last 10 years along with our answers of course:

Is the alkaline filter another stage turning the Easy Twist unit into 5 stage or is this replacing one of the filter stages?

The added Alkaline filter will turn our Easy Twist sytem from a 4 stage to a 5 stage system.

How often to change the alkaliser filter and how much?
The Alkaline filter requires changing every 12 month to 2 years depending on use and the type of Alkaline filter.  The USA filter tends to last up to 2 years, the Koren Alkaline filter last between 12-18 months.  This is on average and depends on the amount of use.

With the Easy Twist RO, there is link to replace stage 1 and stage 2 filters but what about stage 4 filter?
With the 4th stage Easy Twist system we reuse the 4th stage as it is only used as a polishing filter.  Stage 2 and stage 4 are identical filters so when it comes time to change them you remove stage 1 & 2 and discard them.  You then remove stage 4 and put it into stage 2 . Then put the new cartridges in stage 1 and 4.

Why choose this unit vs this other Easy Twist RO system? https://www.clearchoicewaterfilters.com.au/5-stage-reverse-osmosis-system/

Both systems will produce high quality Reverse Osmosis water.  The difference between the two is that the 5 Stage RO has a 5th stage built into it already.  The extra stage is a neutralising filter that uses to calcite to add minerals back into the water and balance the pH.  The reason that people will often choose the 4 stage Easy Twist System is just ease of maintenance and space.  The 4 Stage Easy Twist is quite slimline and the cartridges are as easy to change as a light bulb and most people can do themselves.  This eliminates the need to have someone come out annually and change the cartridges.

We are worried the cartridges may not be available in the future eg out of business or shortages.  Are they standard size cartridges 9 and ¾ inches / 248mm that can be purchased elsewhere – if need be?

All of our systems us industry standard sizes

How does the system ensure no bacteria build up inside the storage unit eg bacteria regrowth from water being still once it passes through the membrane into the storage container?

The components which follow the R.O. membrane could support bacterial growth. These include the tank, the post-filter, the faucet, and the post-membrane tubing. However, keep in mind, that at this point there are few nutrients in the water on which the bacteria can grow. Secondly, our postfilter will screen out bacteria which is larger than five microns. Thirdly, as noted above, the Water Quality Association contends that the common bacteria in filters, which is known as heterotrophic plate count (HPC) bacteria, pose little if any health risk. Nevertheless, if you are concerned about bacteria, you might want to drain your tank once a week and sanitize it once a year. You could also let the water run for a few seconds before filling your glass in order to flush out the tubing, the post-filter, and the faucet.   

It says on the website that the membrane supplied is the TFC one but it is not chlorine resistant.  The other kind of membrane is CTA which are chlorine resistant. Why are the CTA membranes not used? Can we get them instead of the TFC?  Is there a down side to using them CTA?

A CTA (Cellulose Triacetate) membrane is a paper by-product membrane bonded to a synthetic layer. Due to its cellulose composition, a CTA membrane requires chlorine in the water source to keep bacteria from forming on it. A CTA membrane has a rejection rate of between 85 – 94%. CTA membranes have an average life expectancy of 18 to 24 months and are considered inferior to TFC Membranes. We offer only TFC (Thin Film Composite) membranes which are made of a synthetic material. A TFC membrane requires the chlorine to be removed prior to the water entering the membrane. A TFC membrane has a rejection percentage rate between 95 – 98% which is much higher than the CTA membrane. A TFC membrane will last between 2 – 5 years. Many hospitals use TFC membranes in their hemo-dialysis (Kidney) machines because of the higher purity water they produce.

RO TroubleShooting

Learn how to service, repair and maintain your reverse osmosis system

RO not shutting off

What to do when a reverse osmosis system continually runs to drain There are many under-sink reverse osmosis units on the market, however they all share common characteristics. Here is a quick run down on the basic operation which will help you identify what the issue...

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