Fresh chemical reagents can help insure accuracy in water testing

You are careful to follow all the manufacturer's directions when performing water testing.

You "swirl" your samples instead of vigorously shaking them to avoid mixing in carbon dioxide or oxygen from the air, which could produce a false result.

You use the plastic cap — not your finger — to cover the sample cell so that residue on your finger doesn't interfere with test results.

You rinse your test block clean after each test so water from one pool doesn't affect tests at another site.

You are careful to take an accurate water sample from your pool: The water is circulating, and the sample is taken from at least 18 inches below the surface and away from return lines.

But all these procedures are useless if you haven't taken proper care of your reagents. There are 3 major areas to watch for in recognizing and preventing reagent deterioration:

Heat/Light:

As with most perishables, reagents need to be stored under controlled conditions. Exposure to extremes of heat or strong ultraviolet light (sunlight) should be avoided. Liquid DPD is especially susceptible.

Following these helpful storage techniques will help increase the shelf life of reagents:

Store out of direct sunlight at temperature between 36 and 85 degrees Fahrenheit.
Tighten bottle caps after each use.
Keep reagents in their original case.

Freezing:

In colder climates, a delivery can be received where the reagents may have frozen. Follow these guidelines when deciding whether to discard frozen reagents:

Dispose of reagents if the liquid has been forced out of the bottle because of expansion by freezing.
Thaw the reagents at room temperature only. Never place in an oven or microwave to defrost.
If, after thawing, all the reagent returns to a clear solution, the reagent can be used. However, if there are particles or suspended solids remaining that will not dissolve, the reagent should be discarded.

Time:

Unfortunately, there is no definite answer to how long your reagent will last. Some will last indefinitely, while other have limited shelf life. Properly recapping the reagent after use with proper storage will assist in prolonging the shelf life of any reagent.

In general, colored dyes have a shorter life than colorless reagents.
Oxidizing or reducing reagents (often contained in brown bottles) are often prone to shorter shelf lives.
In most cases, acids and bases last indefinitely.

Other signs that reagents may require replacement include a change in color or shade of a colored indicator, staining of the plastic bottle, deposit formation (either suspended or on the bottom of the reagent bottle), and crusts of chemical usually deposited in an area of the bottle cap. Any reagent exhibiting such signs should be viewed with suspicion.

The price of reagents makes it a good investment and wise policy to replace all of them at the start of each swimming season.