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How Does pH Affect Water?

The most common water quality test conducted by scientists is a pH test. pH stands for "potential Hydrogen," and different types of waters have expected ranges of pH. Maintaining the proper pH in streams is important for fish and other aquatic organisms. Maintaining appropriate pH levels in drinking water is important to avoid corrosion in pipes. There are ongoing concerns throughout the world about the effects of damaging acid rain. Understanding how pH affects water resources is an important area of study.

  1. How pH Affects Drinking Water

    • The U.S. Environmental Protection Agency recommends drinking water be in the range of 6.5 to 8.5. Hard water, or water with a high pH, contains a high concentration of dissolved minerals. While healthy for our bodies, minerals such as calcium can cause problems with deposition on ceramic surfaces and bitter taste. Minerals deposit on bathtubs and appliances and leave a scaly residue. Soft water, or water with a low pH, tends to carry higher concentrations of metals such as manganese and iron. These metals have the potential to corrode pipes in older houses.

    Importance of pH in Streams and Lakes

    • Maintaining a balanced pH in waters is critical for aquatic health. Fish and other organisms depend on high-quality water with just the right amount of dissolved oxygen and nutrients. A high or low pH can disrupt the balance of chemicals in the water and mobilize contaminants, causing toxic conditions. Aquatic organisms can experience problems with declining populations and morbidity. For this reason, pH is often sampled by water quality scientists to determine the health of streams, lakes, rivers and groundwater.

    Factors That Cause pH to Vary

    • Pollution is a large contributor to the change in pH of natural waters. Rainwater with a very low pH, called acid rain, causes environmental problems that harm animals, plants and humans. In addition to acidity caused by precipitation, contaminants can enter water through atmospheric deposition. Many environmental laws and regulations now are emerging to manage and control the harmful effects of contaminants in water.

    Understanding How to Test for pH

    • To understand how small changes in pH affect water, it is helpful to understand how scientists measure it. Two commonly used methods are pH meters and litmus paper. Scientists use pH meters by placing a sample of water in a beaker and inserting the probe of the pH meter into the sample and reading an electronic display. The litmus paper method is less accurate but is simple to use. A drop of the water sample is placed on the litmus paper and the strip turns a color. The color is then compared to a chart of pH values.

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