3 Common Misconceptions About Reverse Osmosis Water Filters

  • They remove minerals from drinking water.

Reverse osmosis does remove minerals from water. The process is unable to distinguish between good or bad particles, and simply removes anything and everything over a certain size. What this means is that the harmful particles are stripped away, as well as up to 89% of the healthy minerals like calcium, and magnesium. There is a simple remedy to this problem though, which we’ll talk about shortly.

The point should be made though, that we don’t rely on minerals from water to meet our daily requirements. A study on calcium supplementation stated that “calcium-rich mineral waters seem to offer an interesting, effective alternative to calcium supplementation from milk and dairy products..”. The word “alternative” is key here, as we rely on a balanced diet, which contains nuts, dairy products, and vegetables (among many other things) to get our daily fix of healthy minerals like calcium.

However, I did allude to a solution, and here it is: Most RO systems are available with an alkaline filter. This filter acts as the last stage of the process. After healthy minerals are stripped away by the reverse osmosis membrane, calcium and magnesium are then added back at the end. This replenishes the mineral levels and means your water can taste great again.

  •  It is a really wasteful process.

Again, this statement is true to a certain extent, but it doesn’t have to be the case for everyone. Poorly designed and cheap reverse osmosis systems have been known to waste around 15 gallons of water for every 1 gallon of clean drinking water produced. Now, that’s an amount of wastewater that would not sit well with my conscience. The more efficient systems on the market reduce this figure to around 3:1, which is a whole lot better, but not ideal. To lower this figure even further, to around 1:1, then your system needs a permeate pump. These pumps are ideal for systems with low water pressure, but also have a really positive effect on system efficiency. Again, these pumps are available with almost all of the market leading systems.

  •  Reverse osmosis systems make the water acidic.

This statement has some truth in it too, and an RO system will probably lower the pH of your water supply. Healthy minerals like magnesium and calcium, which are removed by the process, are also alkaline in nature. This means that in high concentrations they have the effect of making the water slightly alkaline, which is considered by some to be healthier water. By removing them, the pH will drop as a consequence. Now whether the water will become slightly acidic (pH<7) depends on your original water supply, but some kind of drop in pH is definitely possible.

The solution to this is the same as to our first myth. By adding alkaline minerals like magnesium and calcium back to the supply at the end of the process, the pH can recover. That means your water can remain alkaline, if that’s how you like it. So for me, an alkaline or pH filter should be part of any home RO system.


The author is a contributor at Water Filter Answers. A website that provides reviews and advice about reverse osmosis and whole house water filters, besides information about water pollution and the environment.