Ask the right questions before choosing a water testing lab for food safety

When choosing a water testing lab to determine surface water quality to comply with food safety laws, consider asking the lab these key questions before choosing.

Photo by Phil Tocco, MSU Extension
Photo by Phil Tocco, MSU Extension

Choosing a water testing lab to determine surface water quality to comply with food safety laws may seem straightforward. It isn’t. With the introduction of the U.S. Food and Drug Administration’s (FDA) Food Safety Modernization Act (FSMA), small differences may have a big impact on whether or not your results are acceptable to an inspector or not. Knowing the answers to some key questions in advance of sending samples in can make all the difference.

Do you test for generic E. coli with enumeration?

Many labs may test for fecal coliform or even generic E. coli presence or absence. Neither of these tests are adequate enough to meet FSMA testing standards. A test that is enumerated provides the actual number of generic E. coli and can be used to determine whether your water source is over threshold.

Do you test in-house or do you send the water sample to another lab?

Sample holding times for generic E. coli tests are, at most, eight hours. You are measuring live organisms that can either multiply or die over time, altering the validity of the test. Sending out the test almost always will make the test void, as the time between taking the sample and having it processed will always be longer than eight hours.

Do you use the Colilert test or the modified m-TEC test?

For smaller labs, the Colilert test provides fewer hurdles to offering the service of testing generic E. coli with enumeration. Unfortunately, as of March 29, 2016, this test is not accepted as valid by the FDA for use as a measure of generic E. coli in water. The Modified m-TEC test method 1603 is acceptable under FSMA.

Are you equipped to test surface water, or water with some measure of turbidity?

Not all labs can handle samples that aren’t near drinking water clarity and quality. Surface water samples may come in hazy or turbid with some suspended solids. These suspended solids can throw off some labs considerably and make testing impossible. More importantly, a lab may not even know to ask whether your sample is a surface water source when it is delivered.

Asking the right questions first can save growers time and money later. What tests are acceptable to meet FSMA standards may broaden, but there are no guarantees. Making sure the tests are analyzed based on current understanding is a solid first step to compliance.

If you have specific questions about the produce rule or have difficulty tailoring GAPs to your farm, contact the Agrifood Safety Workgroup at 517-788-4292 or

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