Whether they are liquids, powders, crystals, tablets, or test-strip pads, all reagents have a shelf life. As a rule of thumb, powders and crystals are very stable if they are kept dry. Acids also tend to have long life spans. When it comes to a reagent’s shelf life, its date of manufacture is not the controlling factor. In fact, storage conditions are more important. Like all perishables, reagents are sensitive to environmental influences.

The experts at Taylor Water Technologies recommend:

• Storing reagents at a consistent temperature in the range of 36°F-85°F; extreme temperature fluctuation, say from a refrigerator to a hot car trunk, causes reagents to deteriorate.

• Keeping reagents out of prolonged direct sunlight. (Note: Brown plastic bottles help protect very light-sensitive reagents.)

• Segregating reagents from containers of treatment chemicals.

• Replacing caps immediately and tightening them carefully so exposure to air and humidity is limited.

• Avoiding switching bottle caps, placing bottle caps on soiled surfaces, repouring reagents into contaminated containers, or touching test strip pads.

Taylor formulates its reagents to remain effective for at least one year, with only very few exceptions (molybdenum indicator in liquid form is one; after it is four months old, it should be tested against a standard periodically). As a general precaution, replace all reagents more than one year old or at the beginning of a new testing season.

For all of these reasons, Taylor advises users to consider carefully the container size when purchasing reagents. Larger bottles may appear to be the better value, but if you do not use them in a year’s time you may end up discarding reagent or risk exceeding the reagent’s useful life. Taylor’s dropper tips dispense 25 drops per milliliter. That means many tests requiring 5 drops of reagent per test will get 110 tests out of a .75 oz. bottle, or 300 tests out of a 2 oz. bottle. While homeowners might consider purchasing .75 oz. reagent bottles, service professionals should probably be using 2 oz. bottles. Repouring from larger bottles (pints, quarts, or gallons) should be reserved for service companies with multiple technicians and retail stores doing high-volume testing. When repouring, it is best practice to replace the reagent’s dropper tip after approximately 8 refills.