Water Testing

Definition and Applications    Types of Measurement     Turbidity Measurement Tips

Definition and Applications

Water testing is the continous sampling of various liquid streams and the analysis of their quality. These liquid streams include watercourses such as rivers and lakes, groundwater, recirculated cooling streams, boiler feedwater or condensate, and process effluents.

Water testing is not only a vital element of preserving a safe public drinking supply and a healthy environment, it can also improve industrial process efficiency for better products at reduced cost.

Types of Measurement

Our selection of water testing equipment includes test kits for bacteria and chemical compounds; colorimeters; multiparameter meters for measuring pH, ORP, conductivity/ salinity/total dissolved solids (TDS), dissolved oxygen (DO), and temperature; and turbidimeters.

Bacterial Test Kits

Eliminate time-consuming culture/plating techniques for convenient bacterial counts and assays.


Measure the light absorbed by your sample after it reacts with a reagent that produces a color change. Since the intensity of absorbed light is proportional to the concentration of the compound, colorimeters accurately indicate the concentration of various compounds in your sample. Many colorimeters work with specific test kits for easy analysis. This reduces operator error, whether in reading color changes or in measuring reagents.

Multiparameter Meters

Measure pH, ORP, conductivity/salinity/total dissolved solids (TDS), and/or dissolved oxygen (DO)/biological oxygen demand (BOD).

Test Kits for Chemical Compounds

Contain prepared reagents and standards that let you easily determine the concentration of specific compounds in the sample. We offer titrimetric and colorimetric test kits for several compounds including ammonia, chlorine, carbon dioxide, heavy metals, and many others.

Colorimetric test kits: These tests determine the concentration of a substance. The higher the concentration of a substance, the darker the color developed in the test.

Other elements can interfere with the accuracy of the tests. Read kit instructions for appropriate adjustments.

Titrimetric test kits: The concentration of a substance in a sample solution can be determined by titrimetic tests. After the sample is treated with an indicator, a standard titrant is added until a color change indicates a completed reaction. The amount of titrant used coresponds to the concentration of the substance being tested.


Turbidity in water is caused by suspended and colloidal matter such as clay, silt, finely divided organic and inorganic matter, and plankton and other microscopic organisms.

Quantify the turbidity of your sample by measuring the light scattered at a 90¡ angle to a source light beam. The meter compares the light scattered by sample particulates to light-scattered in a fluid with known turbidity and displays the measurement in nephelometric turbity units (NTU). The presence of dissolved, color-causing substances that absorb light may cause a negative interference.

Turbidimeters with scattered-light detectors located at 90° to the incident beam are called nephelometers. Nephelometers are relatively unaffected by small differences in design parameters and therefore are specified as the standard instrument for measurement of low turbidities. Poor measurement technique can have a greater effect on measurement error than small differences in instrument design.

Turbidity Measurement Tips

Determine turbidity as soon as possible after sample is collected to ensure examination under original conditions.

  1. Gently agitate samples to ensure a representative measurement. If storage is required, cool to 4°C to minimize microbiological decomposition of solids.
  2. Keep cells scrupulously clean, inside and out, and discard if scratched or etched. Never handle them near the instrument's light beam.
  3. Fill cells with samples and standards—allow sufficient time for bubbles to escape. Because small differences between sample cells can significantly impact measurement, use either matched pairs of cells or the same cell for both standardization and sample measurement.

Coagulation-Flocculation Jar Test of Water: This is a general procedure for the evaluation of a treatment to reduce dissolved, suspended, colloidal, and nonsettleable matter from water by chemical coagulation-flocculation, followed by gravity settling. The practice provides a systematic evaluation of the variables normally encountered in the coagulation-flocculation process. The coagulation-flocculation test is carried out to determine the chemical, dosages, and conditions required to achieve optimum results. The primary variables to be investigated using the recommended practice include, (but are not limited to): chemical additives, pH, temperature, and the order of addition and mixing conditions.

Significance: This jar test permits the evaluation of various coagulants and coagulant aids used in the treatment of water and waste water for the same water and the same experimental conditions. The effects of concentration of the coagulants and coagulant aids and their order of addition can also be evaluated by this practice.