Why is Rain Water Acidic (low pH)??

Millions of people have lived long healthy lives drinking rainwater but that’s doesn’t mean that rainwater is completely pure, or completely safe for everyone to drink.

Potassium, Sodium, Suphur Tetroxide, Nitrus Oxide, Chlorine, Fluorine, Lead, Iron, Bromine, Manganese, Vanadium, Aluminium. These chemicals are generally in, safe extremely low concentrations. The following elements and chemicals are commonly found in rain: Hydrogen, Ammonium, Calcium, Magnesium, Carbonic Acid Rainwater pH is typically acidic with a pH in the range around 5.0 – 5.6. With local thunderstorms the pH can drop as low as 2.0.

This acidity is primarily due to the presence of strong acids, sulfuric acid (H2SO4), nitric acid (HNO3) and carbonic acid (H2CO3). Although some of these contaminants are from pollution many of them are as a result of natural processes.

Rainwater collected in storage tanks is affected by the material quality of the tanks. Plastic tanks, even food grade plastic tanks, essentially store rainwater in the same state as it falls from the sky, unless it is contaminated by contact with metal or organic Substances which change the water chemistry. In particular rain water stored in plastic tanks is almost always acidic with a pH of below 6.0 on the pH scale, but sometimes as low as 5.0. The reason for the acidity of the water in PVC tanks is twofold; as described above the atmospheric effect on rain in considerable however the additional effect of phthalates can’t be discounted.

Acidic water can be neutralised by the use of a Calcite unit which naturally adjusts the pH to neutral. Removing phthalates can also be accomplished by using carbon block filtration or reverse osmosis water purification.  Call PurePro today if you want more information on purifying rain water.


A recent case of copper poisoning is said to be caused by acidic rainwater from plastic tanks corroding household copper water pipes.  There is nothing wrong with the water, however rainwater collected in plastic and plastic lined water tanks remains naturally acidic and can react with the copper pipes that carry the water to your household taps. Its usually not an issue with concrete tanks as they leach lime into the water, reducing the acidity and therefore reduces its corrosion of copper pipes. Dissolved copper in drinking water causes gastric problems and headaches, and in severe cases cirrhosis of the liver.  Click on link for the full article!

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