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University of Minnesota Extension

Testing well water for fruit and vegetable production

Quick facts

  • Water used for handwashing, produce washing and rinsing, frost protection, irrigation, drinking and other uses on the farm should be tested.

  • When testing water, labs look for harmful pathogens such as total generic E. coli. E. coli is an indicator of fecal contamination in your water.

  • It is important to properly collect the water for testing for an accurate result.

Let the water run for 3 minutes before taking a sample to ensure you are testing the water from the well.

Testing your farm’s water for the presence of E.coli is an important part of you farm’s food safety plan. Water tests also help you determine a baseline so you know if something has changed in your water.

E. coli is an example of a harmful pathogen that can be present in water and cause foodborne illness, making people sick. Water used for handwashing, produce washing and rinsing, frost protection, irrigation, drinking and other uses on the farm should be tested.

How frequently should I test my water?

The frequency of water testing is determined by the source of the water.

Well water should be tested at least one time per year, but three times per year will give a better idea of the water quality.  Test at the beginning of the season, and then during and after harvest.

Municipal water does not need to be tested, but a water bill proving that water comes from a municipal source will be needed if your farm is seeking a GAP audit inspection.

Surface water should be tested at least three times per season. It should be tested at the start of the season, during peak use, and prior to harvest. Regardless of testing, surface water should be used only with great caution, and applied only with drip irrigation.

The FSMA Produce Safety Rule requires that agricultural water be tested for generic E. coli. Your buyer or organic inspector may ask for other tests, but the basic test to indicate the safety of your water is generic E. coli. It should be 0 for postharvest uses. There are allowances for water used for irrigation purposes. Learn more about water analysis method requirement (PDF) for FSMA Produce Safety Rule.

How to collect water for testing

  • Water should be collected as close to the source as possible (from the pump or hydrant).

  • Call ahead to the lab you will use for the testing. The lab will send you collection bottles or whirly bags (separate ones for coliform bacteria and nitrates/nitrites).

  • Follow the directions included with the sample containers.

  • Keep the sample cool and return it within the hold time indicated by the lab.

  • Labs can be private or county-operated.

A complete list of certified laboratories is available from the Minnesota Department of Health.

Michele Schermann, former Extension educator and Annalisa Hultberg, Extension educator

Support for this project was provided to the Minnesota Fruit and Vegetable Growers Association through the Specialty Crop Block Grant Program – Farm Bill, through the Minnesota Department of Agriculture and the USDA – AMS. These institutions are equal opportunity providers.

Reviewed in 2018

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