As a rule, you probably don't give a lot of thought to your horses drinking water, but it does have a direct influence on his health and well-being. Dissolved in that clear liquid are minerals absorbed from the environment the water flows through, as well as chemical contaminants and bacteria picked up along the way.

Much as we'd like to believe that the water our horses consume is "pure," the truth is that water completely untouched by chemicals or minerals doesn't exist in nature. Water is, after all, the universal solvent, with a unique ability to pick up and dissolve virtually everything it comes in contact with. The substances contained in drinking water aren't necessarily bad; minerals dissolved in water impart much of its flavor, and many are beneficial, such as fluoride in city water supplies.

Instead of worrying about water purity, focus on whether it's safe for our horses to drink – that none of its contents are infectious or toxic.

Location Affects Water Supply

If you live in suburbia, your barn may draw its water from a public or municipal system that provides extensive purification and filtration services, and also regularly tests its water for contaminants. Worries are few with this type of system, but there are no guarantees. The testing is done at the source, but damage to the delivery line, or a problem with the plumbing on your property, could taint your water.

Living in the country is a different deal. More diligence is required if, like the majority of horse owners, you draw your barn's water from a well. An annual Total Coliform test is a good idea for all wells. The test checks the water for bacteria that normally are found in the soil, in surface water and in human and animal waste.

A few coliform bacteria are not, in themselves, considered harmful, but their presence in your water supply is an indication that your well may be contaminated by run-off from your manure pile or a nearby septic bed tank. Coliform levels rise in drought conditions, when there's a sudden heavy rainfall or when there is any unusual change in weather patterns. It's also possible to have high coliform levels when the well has physical defects, such as a broken or missing cap that could allow debris, surface water, insects, or rodents inside.

When To Do Bacterial Testing

There is a noticeable change in the color or odor of your water.

When you open a new water source prior to watering your horses.

Any animal or person on your farm becomes sick from a water-borne disease. Potomac Horse Fever, for example, is suspected of being water-borne, through freshwater snails.

The water supply system on your property has been disassembled for repairs to the well, the pipes, or the pump.

Flooding occurs near your well.

The cap or the interior of the well has been damaged.

The area is recovering from an extensive drought.

Wells that are correctly drilled, well protected, and more than 50 feet deep generally have less chance of becoming contaminated with bacteria. If you have such a well and several previous bacterial tests have come back negative, you may need to test every 2 to 3 years. Water from an old or shallow well should be tested more frequently.

An agricultural extension agent or an agricultural university can conduct water testing for coliform bacteria. Some private labs also offer water testing. When you contact a lab about water testing make sure you follow its instructions for collecting your sample meticulously. Incorrect collection procedures can easily contaminate your water sample and lead to false test results.

Minerals: Good News or Bad?

Bacteria aren't the only concern with drinking water. The mineral content can influence its taste, smell, and palatability. The classic example is "sulfur water," which has that characteristic rotten-egg odor. Minerals are rarely toxic from water. However, if you have a concern, a lab can test your water for levels of calcium, magnesium, manganese, iron, copper, zinc, sodium, chloride, and lead, as well as sulfates and nitrates. Concentrations of these minerals, if sufficiently high, can have an impact on your horse's dietary balance because levels of one mineral in his system often can influence his ability to absorb another. Water can provide all the iodide, and from 4 to 20 percent of the daily requirements for salt, calcium, magnesium, manganese, cobalt, and sulfur, but less than 1 percent of other minerals.

Iron is a mineral that is often found in high concentrations in well water. It can stain your water a red or rusty color and leave it with a metallic taste. Iron also is sometimes accompanied by "iron bacteria," which consume iron in the water and, in the process, exude a rust-colored slime that coats the insides of your pipes and fixtures. If iron bacteria are present in your well, you may be looking at total, repeated disinfections.

Lead is a potentially toxic mineral that easily finds its way into the water supply. The tolerable levels of lead in water for horses (less than 0.1 parts per million) are one of the lowest for all minerals. Old lead pipes and soldering may increase lead concentrations in water to dangerous levels. Lead toxicity from horses rarely if ever comes from the water supply. However, the long-term impact of low-level ingestion is unknown in horses. The effects of high lead levels in humans is better understood than the impact on horses, but it's best to avoid a risky situation. A calcite filter is an effective way to decrease the corrosiveness of well water and thus lower the lead levels.

Calcium and/or magnesium salts are to blame if your water is "hard." Though hard water – up to a level of about 100 parts per million of salts – isn't a major problem, at high concentrations magnesium salts have been known to trigger mild diarrhea.

You also might conduct an acidity/alkalinity test. Water that tests below pH 6.5 is considered acidic and can contribute to the corrosion of your pipes. If your water tests at pH 8.5 or higher, it's alkaline, which means you probably have crusty mineral deposits on your pipes and fixtures. A sudden change in your water's pH may indicate damage to your well or below-ground corrosion. Alkalinity may make the water taste salty and affect palatability, but it is not outright toxic.

Consider testing your water once every 3 years for total dissolved solids, or TDS. TDS is a measure of the solids dissolved in your water, and high levels (more than 1,000 parts per million) are generally linked with water that has an offensive smell, taste, or color. It also may contribute to health problems. At farms where TDS levels are high, equine diarrhea is a common complaint.

Turbidity is a related water test that can help you identify the suspended solids in your water that make it look cloudy. Mud, algae and iron are three likely culprits.

Testing Recommendations

If you live in an agricultural area where crops and/or livestock are raised, test for pH, nitrates, and possibly pesticides.

If your water has an unpleasant smell, test for pH, copper, lead, iron, zinc, sodium, chloride, TDS, and hydrogen sulfide.

If your water is cloudy and frothy, test for turbidity, TDS, and detergents.

If you live near a road salt storage site, a street that is heavily salted in winter, or the coastline, test for sodium and chloride levels.

What To Do If You Have Contamination

Eliminate the source of the contamination, which might be as simple as moving the manure pile.

Better protect your well by giving it a weatherproof, sanitary seal and eliminating access for debris, insects, and rodents.

Treat the water with chemicals or filtration to improve its quality, if that's what your lab recommends.

Consider drilling a new well.