If water looks clean, it’s generally considered to be safe. However, water-quality surveys show that even clean-looking water may contain some detrimental substances. The question is at what point does it become a concern for pigs? 

There’s no simple answer. Factors that can influence water quality include pH, salinity, nitrates and nitrites, toxic inorganic chemicals, organic toxins and microbial contamination.

The pH is a measure of water’s acidity or alkalinity. While a low pH (2) would represent extremely high acidity, a high pH (12) would indicate high alkalinity.  Water provided to pigs should have a pH range from 6 to 8. The pH level can affect water-soluble antibiotics and chlorination. The higher the pH, the less effective chlorination will be as a bacterial-control agent.

Water hardness is caused by mineral salts of calcium and magnesium. It is reported as calcium carbonate in grains per gallon or milligrams per liter, which is the same as parts per million. The hardness of water is considered “average” at less than 120 ppm; anything greater than that is considered hard water.  Low levels of strontium, iron, aluminum, zinc and magnesium salts are not detrimental to pig health, since pigs can tolerate and use these minerals. Concentrations of these salts are seldom too high to be tolerated.  However, very high calcium levels in water may require higher levels of dietary phosphorus to avoid a calcium-phosphorus imbalance.

Concentrations of all constituents dissolved in water are called total-dissolved solids. Salinity commonly involves calcium, magnesium and sodium in the bicarbonate, chloride or sulfate form.  Water containing less than 5,000 ppm sulfate and 6,000 ppm total-dissolved solids may cause temporary diarrhea in pigs and increase daily water intake. However, health and performance are not greatly affected.

Sulfates greater than 1,000 mg per liter of water may cause modest to severe diarrhea in pigs, with just-weaned pigs the most susceptible. Canadian researchers have found that high sulfate levels in the drinking water can alter the environment of the small intestine. This may act as a stress component when intestinal pathogens or irritants are encountered, resulting in performance declines.

Much of the research to evaluate sulfate and nitrate effects on pig performance has involved tap water (for human consumption) with added salts. This may not adequately simulate on-farm water conditions, since water usually contains a mixture of substances, which may have a detrimental effect on pig performance.

Nitrates are widely dispersed in our environment and can cause health hazards when significant amounts are present in drinking water. While hogs easily tolerate nitrate levels commonly found in drinking water, nitrite (nitrate in a reduced form) is readily absorbed and can be toxic. At toxic levels, nitrite oxidizes the iron in hemoglobin and reduces the blood’s oxygen-carrying capacity. For pigs, bacterial conversion of the nitrate must occur for the nitrite form to be present in significant amounts.

Water’s general sanitary quality can be determined through bacterial examination. Results are reported as a number of coliforms per 100 ml of water. Coliforms’ presence in a water sample indicates organic contamination. This often occurs at the well head due to runoff from feedlots or other animal areas. Bacterial contamination should be less than 100 coliforms per 100 ml for adult livestock and 1 coliform per 100 ml for young livestock.

Bacterial contamination of water is usually associated with other types of contamination such as nitrates, dissolved organic matter or sediment. Older wells may not be constructed properly, the well top may not be sealed, there may be casing leaks or it may be an old-style well pit. Wells located near a depression, drainage channel, flood plain, feedlot, septic tank or septic tank drain field are susceptible to contamination, and it can vary with rainfall amounts.

Water also can harbor and spread disease pathogens such as Leptospira, Salmonella and Coccidial parasites. If there’s a question, tests can help isolate these organisms to determine if there’s a link between water contamination and animal health.

So, sight alone is not a sure thing when it comes to delivering quality water.