pH is a measure of how acidic or basic (alkaline) the water is. The pH scale ranges from 0 (very acidic) to 14 (very basic), with 7 being neutral. The pH of natural water is usually between 6.5 and 8.2. Testing water for pH measures the capacity of the water to neutralize acids associated with pollution.

pH is one of the primary indicators used for evaluation of surface-water quality. Most aquatic plants and animals are sensitive to pH variations. Water's pH is affected by the minerals dissolved in the water, aerosols and dust from the air, and human-made wastes as well as by plants and animals through photosynthesis and respiration.

Several factors affect the pH of the water, including algal blooms, bacterial activity, water turbulence, chemicals flowing into the waterbody, sewage overflows, impacts from land pollution, accidental spills, and acid rain.

1. Fill the test tube (0106) to the 10 mL line with the water sample.
2. Add one pH Wide Range TesTab (6459).
3. Cap and mix by inverting until the tablet has disintegrated. Bits of material may remain in the sample.
4. Compare the color of the sample to the pH color chart.
5. Record the result as pH.

• 4 Poor
• 5 Poor
• 6 Good
• 7 Excellent
• 8 Good
• 9 Poor
• 10 Poor

Most aquatic organisms are adapted to a very specific pH level and may die if it changes even slightly. Therefore, the pH of water is critical to the survival of most aquatic plants and animals. pH values between 7 and 8 are optimal for supporting a diverse aquatic ecosystem. A pH range between 6.5 and 8.5 is generally suitable. Many species have trouble surviving if pH levels drop under 5 or rise above 9.