You are thinking of buying a reverse osmosis system. You did your research and ran across sayings out there about RO water being acidic is not good for you. You start to be concerned and even debate whether you should add a alkaline polishing filter or avoid reverse osmosis system at all.
But does pH in your RO water really matter?
What is pH?
First of all, let’s understand what is pH. pH is a measure of the relative concentration of free hydrogen ions in the water. Water that has more free hydrogen ions is acidic, whereas water that has less hydrogen ions is alkaline. pH is usually within the range of 0-14, but it can be below 0 or above 14 for strong acid or strong base. pH is logarithmic, which means that for every unit change in PH, the level of hydrogen ion concentration is 10 times different. For example, the concentration of hydrogen ion in water with a pH of 6 is 10 times more than that in water with a pH of 7.
How does RO water get to be acidic?
We all know that water in its pure form is H2O. And in its pure form water has a pH of 7. Reverse osmosis filtration will actually filter out most of impurities in water, and return water close to its pure form. So RO water without any contamination should have a pH close to 7. But pure water is very hungry. As soon as RO water is in contact with air, it grabs H2O in the air quickly in the following reaction:
CO2 + H2O --> HCO3 + H+
With hydrogen ion increases in its concentration, RO water becomes acidic and usually ends up with a pH level of around 6.
Is acidic water bad for your health?
Is pH 6 really bad for your health? The simple answer is NO. Consider the pH of the daily necessities and put it into perspective. Vinegar has a pH of 2, citrus drink has a pH of 3, carbonated water has a pH of 4.5, black coffee has a pH of 5, and milk has a pH of 6.5. If we think acidic water is harmful, we should not add vinegar, get away from orange juice, avoid Coke, and skip coffee and milk.
Your body likes to stay at around a blood pH of 7.4, which is almost neutral. The pH of your body is regulated by kidney for liquid intake. Without contamination or food poison, your kidney does its job well and pH in liquid intake does not affects your blood pH. In other words, acidity or alkalinity in clean water does not affects your health.
Should we be concerned about acidic water at all?
It depends on the source of the acidity in water. Acidic ground or surface water can mean contamination from sources or activities like mine site, landfill, farm runoff, etc. Acidic water can lead to heavy metal toxicity as acid water mobilizes and leaches metals. Strong acidic water is also corrosive to pipes and equipment. In other words, if your source water is acidic, you may need to look into it and possibly treat it with pH adjustment like Calcite if it is too much out of balance.