Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Water testing is an important part of a produce grower’s food safety program. As new FDA guidelines are released later this year, there will be increased emphasis on water testing for fresh consumed produce.
Growers should be testing irrigation water, water used for application to crops (such as water sources used for filling sprayers), and water sources used for conveying and washing produce. Growers should always use potable water for packing house water and spray water. This is water that meets drinking water standards. Irrigation water needs to meet the EPA recreational water standards (safe for swimming).
Water is tested for organisms that could indicate contamination with fecal matter: E. coli for irrigation water, and total Coliforms and E. coli for potable water. Potable water used in the packing house should be free of both total Coliforms and E. coli. Irrigation water should meet the following standards for surface water (ponds, ditches, streams): no one sample should be greater than 410 colony forming units (CFUs or MPN) and a geometric mean of all samples should be no more than 126 CFUs. Well water used for irrigation should average less than 126 CFUs (geometric mean).
Testing frequency that will be required is still under discussion by the FDA. However, it is currently recommended that growers take several water samples throughout the growing season for surface and well water used in irrigation, prior to the spraying season for spray water, and prior to the packing season for packing house water. All water sources used in the produce operation should be sampled and tested (each well or surface water intake providing water). Surface water used for irrigation should be sampled more frequently than well water used for irrigation.
Laboratories in our region certified to test water for irrigation and potable water include QC Laboratories in New Castle, DE; Agrolab in Harrington, DE; and Water Testing Labs of Maryland located in Salisbury, MD with a pick up location in Seaford, DE.
To take water samples, obtain a sample kit and information sheet from the water testing laboratory (you need a sterile bottle for water collection). Run the pump for at least 30 minutes before sampling making sure fittings have been flushed. Open the outlet at the pump, take the sample from outlet using the sterile sample collection bottle, close the bottle immediately, put the bottle on ice, and deliver within the timeframe recommended from the lab (same day). Request a generic E. coli quantitative test for irrigation water and a drinking water test for packing house, drinking, and spray water.