Alkalinity & Acidity

pH - Alkalinity & Acidity

The pH of water describes the hydrogen-ion activity. The pH scale ranges between 0 and 14 with 7 being neutral, less than 7 acidic and greater than 7 alkaline or base. Water with a pH of 10 is ten times as alkaline as a pH of 9. It is an exponential function. Alkaline water may be due to the presence of one or more ions, such as hydroxides, carbonates and bicarbonates. Strongly alkaline waters have an objectionable "soda" taste and feel "slippery". Alkaline water can cause excessively dry skin. Troublesome amounts of alkalinity can be removed by reverse osmosis.

Acidic water can cause serious corrosion of metal pipes and metal fixtures, and if low enough, will give a "sour" taste to water. A pH of between 5 and 7 can be treated with a neutralizer. As the water moves through the bed, it reacts with the filter material -- usually a mixture of calcite and corosex. Operating costs for this type of filter are nominal. Water with a pH lower than 5.0 is normally treated with an injected solution of soda ash that raises the pH to between 7.0 and 8.0.

Corrosion

Corrosion is the eating away of metals due to electromechanical action. Oxygen causes rust to form on many types of metal. Acidic water can also cause corrosion. Galvanic corrosion occurs when two pipes of dissimilar metals are joined directly without the use of a pipe fitting designed to insulate different metals from one another.

Factors, such as temperature, can exacerbate water that tends to corrode. Temperature can increase the rate of corrosion three to four times the normal rate when the temperature of the water is increased from 60 F to 140 F.

Corrosive water can be treated in a number of ways. A neutralizer uses calcite and corosex to neutralize the acidic quality of water.

Polyphosphates are used to form a thin, tight film on pipe walls that works almost like a glass coating keeping water away from metals that may corrode. This can be done in two ways. The first method uses a chemical feed pump to inject a chemical into the water to neutralize it. The second method uses a small tank that combines polyphosphates with calcium and magnesium. A mixing tank is advised to allow for an even dosage of polyphosphates.