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

Compact, rugged, and easy to use on-the-go pH measurement. Hach's portable pH meters offer accuracy, convenience and reliability.

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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 EPA 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
    $63.00

    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.

    Wide Range pH Indicator Solution, 1 L
    This product is eligible for a recurring order.
    2329353
    $112.00
    Wide Range pH Indicator Solution, 500 mL
    This product is eligible for a recurring order.
    2329649
    $58.85
    Phenol Red Indicator Solution, Spec. Grade, 50 mL
    This product is eligible for a recurring order.
    2657512
    $20.85
    Wide Range pH Indicator Solution, 100 mL MDB
    This product is eligible for a recurring order.
    2329332
    $30.69
    Phenol Red Indicator Solution, 100 mL MDB
    This product is eligible for a recurring order.
    21132
    $23.09
    Thymol blue indicator solution, 100 mL MDB
    This product is eligible for a recurring order.
    25732
    $30.69
    Phenol Red Indicator Solution, 50 mL SCDB
    This product is eligible for a recurring order.
    21126
    $19.85
    Phenol Red Indicator Solution, 500 mL
    This product is eligible for a recurring order.
    21149
    $47.95
    Bromthymol Blue Indicator Solution, 100 mL MDB
    This product is eligible for a recurring order.
    25532
    $24.05
    Bromthymol blue indicator solution, 500 mL
    This product is eligible for a recurring order.
    25549
    $47.95
    Bromcresol purple indicator solution, 100 mL MDB
    This product is eligible for a recurring order.
    25432
    $29.59
    TKN Indicator Solution, 50 mL SCDB
    This product is eligible for a recurring order.
    2251926
    $21.75
    Thymolphthalein Indicator Solution, 1 g/L, 15 mL SCDB
    This product is eligible for a recurring order.
    2185336
    $28.85
    Bromcresol Green Indicator Solution, 500 mL
    This product is eligible for a recurring order.
    2329549
    $80.99
    Bromcresol Green Indicator Solution, 100 mL
    This product is eligible for a recurring order.
    2700742
    $37.69
    Bromphenol Blue Indicator Solution, 100 mL MDB
    This product is eligible for a recurring order.
    1455232
    $26.35
    Methyl orange indicator solution, 100 mL MDB
    This product is eligible for a recurring order.
    14832
    $18.95
    Methyl orange indicator solution, 500 mL
    This product is eligible for a recurring order.
    14849
    $31.25
    Phenolphthalein Indicator Solution, 5 g/L, 100 mL MDB (APHA)
    This product is eligible for a recurring order.
    16232
    $20.79
    Phenolphthalein indicator solution, 5 g/L, 15 mL SCDB (APHA)
    This product is eligible for a recurring order.
    16236
    $19.25
    Phenolphthalein indicator solution, 5 g/L, 1 L (APHA)
    This product is eligible for a recurring order.
    16253
    $51.45
    Phenolphthalein indicator solution, 1 g/L, 15 mL
    This product is eligible for a recurring order.
    189736
    $16.99
    Phenolphthalein indicator solution, 1 g/L, 1 L
    This product is eligible for a recurring order.
    189753
    $47.35
    Phenolphthalein Indicator Solution, 100 mL
    This product is eligible for a recurring order.
    2330242
    $19.59
    m-Nitrophenol Indicator Solution, 100 mL DB
    This product is eligible for a recurring order.
    247632
    $35.29
    Bromcresol Green-Methyl Red Indicator Solution, 100 mL MDB
    This product is eligible for a recurring order.
    2329232
    $29.45
    Bromcresol Green-Methyl Red Indicator Solution, 500 mL
    This product is eligible for a recurring order.
    2329249
    $46.49
    Methyl Purple Indicator Solution, 100 mL MDB
    This product is eligible for a recurring order.
    2193432
    $29.45

    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
    This product is eligible for a recurring order.
    2569600
    $5,569.00
    pH Test Strip, 7.5-14 pH units, 100 tests
    This product is eligible for a recurring order.
    2751000
    $48.65
    Stream Survey Test Kit
    This product is eligible for a recurring order.
    2712000
    $710.00

    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. This method is not an EPA-approved method for monitoring pH.

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