pH measurement is a key step in many water testing and purification processes. A change in the pH level of water can alter the behavior of chemicals in the water, and pH level affects product quality and consumer safety, so pH is monitored and managed in a wide range of water treatment settings.

pH

What is pH and What Does It Measure?

pH is a measure of the hydrogen ion activity in a solution. Pure water that contains an equal balance of positive hydrogen ions (H+) and negative hydroxide ions (OH-) has a neutral pH.

Featured pH/ORP Analyzers and Testing Products

Portable pH Meters

Portable pH Meter

Simple and affordable pH measurement for home, school, and hobbyist use. Hach's pH testers deliver quick and easy measurements with accurate and reliable results. We also offer pH buffer solutions for our testers.

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Benchtop pH Meters

HQD

Accurate and precise pH measurement for laboratory and industrial applications. Hach's benchtop pH meters offer advanced features and user-friendly interfaces.

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pH / ORP Sensors and Probes

DPD

Select the right sensor or probe for precise pH/ORP measurement. Explore and shop our wide range of solutions that suit your application now.

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Controllers and Transmitters

LXV

Ensure consistent pH control with Hach's reliable suite of controllers and transmitters. Choose from our range of automated solutions for various applications.

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pH Testers

pH tester

Simple and affordable pH measurement for home, school, and hobbyist use. Hach's pH testers deliver quick and easy measurements with accurate and reliable results.

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pH Test Strips

pH Test Strip

Take the guesswork out of pH testing with Hach's pH test strips. Our high-quality strips provide quick and dependable readings for a variety of applications.

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Which Processes Require pH Monitoring?

pH of drinking water is measured at multiple stages in a drinking water plant. Normal pH range for tap water is 6.5-8.5 throughout both treatment process and distribution. Drinking water pH level must be monitored to minimize corrosion, contamination and adverse effects on taste, odor, color and appearance.


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A drinking water treatment plant monitors pH in several stages of water purification.

Methods for Monitoring pH

Potentiometric Method

This method uses a pH sensing system (including a pH meter, a pH sensing electrode and a pH reference electrode) to take an electrochemical measurement to precisely determine where the tested fluid falls on the pH scale.

Advantages

This is the most accurate method for pH measurement. Portable, lab or process/online options are available for this method. This method can be ISO approved for monitoring pH.

Disadvantages

This method requires proper handling, care and maintenance of the pH probe and involves higher instrument costs.

Our online technology course provides more information on the importance of monitoring and measuring pH.

pH Technology
DL-PH-TCH
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Visual Method

An indicator solution changes color when added to the solution being tested. That color change is then visually compared against a color chart to determine pH.

Advantages

This method is simple, inexpensive and portable.

Disadvantages

Solutions being tested with this method must be free of color and have no turbidity. Solutions being tested with this method must not have a secondary reaction with the indicator solution. No online or process options exist for this method. This method does not produce exact measurements.

Liquid Indicator Dyes

Liquid dyes are added directly to the solution to produce a color change that indicates changing pH.

Indicator solution, wide range pH, 1 L
2329353
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Indicator solution, wide range pH, 500 mL
2329649
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Phenol Red Indicator solution, 50 mL
21126
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TKN Indicator Solution, 50 mL SCDB
2251926
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Paper Strips/Test Strips

Dye-infused paper strips are dipped into a solution and then change color to indicate corresponding pH. This method is not affected by color or turbidity in a sample.

MEL/P-A safe drinking water lab
2569600
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pH Test Strip, 7.5-14 pH units, 100 tests
2751000
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Test kit, stream survey
2712000
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Photometric Method

Like the visual method used in test strips and color wheels, an indicator solution is used to create a color change in the solution being tested. However, with this method the color change is not assessed by the human eye, it is measured by a photometer (colorimeter or spectrophotometer) to produce a more precise pH reading.

Advantages

This method is portable, removes the subjectivity of the human eye and does not require complex pH meter calibration.

Disadvantages

Solutions being tested with this method must be colorless. No online/process options exist for this method and there are costs associated with instruments.

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