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Using pH Strips

We all know the taste of something acidic (like a lemon) or something basic (like milk), but did you know that the science behind these tastes has to do with the pH balance? pH is a critical piece of stream health, and it can fluctuate throughout the day in response to photosynthesis, geology, and human activity.

In the graph above, you can see the livable range of pH levels for freshwater fish. A pH of 7.0 is neutral, a pH below 7.0 is acidic, and a pH above 7.0 is basic. pH determines how easily an aquatic organism can use nutrients and indicates how toxic pollutants may be. To qualify as a protected fishery by the Pennsylvania Department of Environmental Protection, a stream must have a pH between 6.0 and 9.0. When pH is outside this range, nutrients become difficult to absorb and pollutants become more toxic, stressing organisms and leading to a reduction in biodiversity. Stream pH is influenced by in-stream photosynthesis, local soil type, geology, and human-based pollution.


In the DCCS program, we study stream health by using Panpeha pH strips, which change color based on the pH of the stream. Below are some tips and tricks to make sure that we are getting the most accurate pH readings:

1) Unlike the chloride strips, pH strips only need to be submerged in the stream sample for a few seconds. If you leave the strip in the water for too long, the indicator colors can run together, making the final value harder to read.

  • In the image on the left, you can see that the colors have bled together, becoming muddy and difficult to read.

2) When comparing the strip to the conversion table, be sure to pay attention to the values. If the pH is below 6 or above 8.5, stream life may be suffering.

  • In the image on the left, Is the value 2.5 or is the comparison being made on the wrong side of the conversion table? For context, distilled vinegar has a pH value of 2.5. You would very likely feel a tingle or a burn when placing your hand in the water and there would be dead plants and stream life by the site.

3) Be sure to take a picture with the pH strip in frame and in focus with the entire conversion table (including the lot number!) and upload with the rest of your data! If the conversion table is not in the image, we are unable to double check your values. Save us an email and please take your pictures with the conversion table in focus!

Left: This is what we want to see - the strip and conversion table are in focus, and the conversion looks accurate.

  • Middle: The strip and conversion table are in focus, but the reading is inaccurate and the strip was left in the water for too long. This is a valuable picture to help us troubleshoot that the reported value was incorrect.

  • Right: This image is not useable. The strip is out of focus and there is no conversion table to check. Please do not upload picture like the example on the right side of the image, as it makes the entire team sad.

4) Lastly, if you are finding it difficult to accurately compare the full range of colors on the pH strip to the chart, please let us know right away and we will find a solution for you!

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