Water is used in many ways on the farm. It plays a vital role in growing fruits and vegetables in order to keep quality high both before and after harvest. For instance, many farms use ice or water to chill or wash produce. The standards for agricultural water and for post-harvest water are different and are based on their impact on produce safety. It is also important to consider water quality when spraying crops.

We know that water serves as an ideal environment for the growth and movement of microbial pathogens. How we use water on the farm can enhance or diminish opportunities for microbial contamination. Fecal material from unfinished compost, manure applications, worker’s hands and clothes, neighboring land use and other sources are the typical origin of that contamination. The farm’s food safety culture will include procedures to ensure that water quality stays high, and contamination risks stay low.

Typically, farms use either municipal, well or surface water. Ensuring good water quality starts at the source and continues throughout the distribution system. If a farm uses more than one water source, a risk assessment will align the water source with the water use to ensure there is a low-to-no risk of contamination. A written water risk assessment is an important part of the MDA Good Agricultural Practices (GAP) certification standards and the Harmonized Good Agricultural Practices (HGAP) standard as well. A written risk assessment is not required to meet the Food Safety Modernization Act Produce Safety Rule (FSMA PSR), but analysis of source and intended use figures heavily in understanding the basic concept that “all agricultural water must be safe and of adequate sanitary quality for its intended use.”

Start with Testing

If municipal water is the primary source, obtaining an annual water quality report from the municipality is all that is necessary. Keep that statement with the farm food safety plan or similar records. In Maryland, municipal water is treated with a sanitizer to maintain potability. Maryland potability standards are: total coliforms, 0 or none, turbidity < 10 NTU1, and nitrates <10 mg/L. Municipal water is ideal for post-harvest use such as ice making, cooling, and washing of fresh produce. Potable water is also used for hand washing and cleaning of food contact surfaces2.

Well water can vary in quality. Deep wells (greater than 40 feet) are often the most consistent in producing good quality water. A water sample taken at the beginning of the season should be tested for generic E. coli if its use is for irrigation only. If well water is used for food contact, test for potability as outlined above. Keep those test records with the farm food safety plan or similar records.

The designation, “surface water” includes any water source that is exposed to the environment. That includes ponds and streams, but also includes springs, rain barrels, and cisterns. Because exposure to the environment increases the risk of microbial contamination, it is recommended that a water sample be taken at various intervals during the growing season. Current MDA GAP standards require one test sample at the beginning of the season, one half-way through the season and the last one right before harvest. Untreated surface water is not appropriate for post-harvest use or for cleaning and sanitation of food contact surfaces.

This interactive map shows the locations of approved water testing labs in Maryland:

The video here: ( covers the basics in taking and processing a surface water sample. More on water quality and testing can be found here:

Currently the FDA has not finalized the water testing standards for the PSR. Until those standards are published, farmers should begin water testing following the GAP standards as outlined above. All test results should be recorded and kept with the farm food safety plan or other farm records.

Inspect and maintain the distribution system

A reliable water source can become contaminated by a poorly maintained distribution system. At the beginning of the season, inspect all pipes, fittings, and hydrants for leaks or excessive wear. If water can leak out, contamination can get in. Make sure you protect your water source by installing back-flow valves on all take-off points in the system. Check for dead-legs in the pack house or other buildings and eliminate them. Map the farm’s water distribution system and create a checklist to make the job easier. More on water risk assessment and distribution system inspections can be found here: MDA GAP, HGAP and the PSR require annual water distribution system inspection. Keep those records with the farm food safety plan or similar records.

Review your water risk assessment annually and adjust as your water use changes. The goal is to reduce the risk of contaminating the water that is used to produce high quality fresh produce. If a Harmonized Gap plan is in your future, detailed information on water assessment can be found here:

To learn more about MDA GAP, HGAP or the Produce Safety Rule, contact, Carol Allen 240-994-5043, 

For more information on HGAP look here:

The code of federal regulations for the Produce Safety Rule (Part 112, Standards for the Growing, Harvesting, Packing, and Holding of Produce for Human Consumption) can be found here:


1NTU, nephelometric turbidity units measure the ease with which light shines through a column of water.

2These would be zone 1 surfaces (see Cleaning and Sanitizing section for more information,