10 Tips for Accurate Water Testing

Balancing spa water becomes a futile task if you don’t know how to test the water properly. Everything from improper storage of test kits to incorrect timing can cause false readings and false readings can prompt you to take the wrong course of action.

First, you need to decide which type of testing method you will use. The most accurate results tend to come from liquid test kits. These kits require you to add drops of chemical reagents to a sample of water from your spa and match the color it yields with those on a chart. An easier method is test strips, which typically require you to dip or swirl a strip in the water sample and match the resulting colors on the strip to the corresponding charts on the test strip bottle.

Test strips are available for measuring chlorine levels, bromine levels, pH, and alkalinity. Liquid test kits are available for measuring those plus calcium hardness.

Most pool and spa dealers offer free professional water testing; all you have to do is bring in a water sample in a clean container. Many dealers will even print out an analysis that tells you precisely which chemicals, and how much of each, to add to your spa.

That said, you will still need to test your water regularly. To ensure the most accurate results for your analysis, follow these guidelines.

Take your WATER SAMPLE from at least 12 to 18 inches (30 to 45 cm) below the surface. Water near the surface often has a lower sanitizer residual than the rest of the water and can have a higher pH due to evaporation and UV rays near the surface. To get a good sample, invert a clean jar or vial and plunge it up to your elbow beneath the surface of the water. Then upright the jar or vial and fill it.

Don’t TAKE WATER samples from near return INLETS.

If the spa has an in-line chemical feeder, the concentration of sanitizer will be higher there than in the rest of the pool or spa.

Test SAMPLES FROM SEVERAL LOCATIONS if your spa has dead spots areas with poor circulation.

ALWAYS USE A CAP, not your fingers, to seal a test jar or vial. Otherwise, contaminants from your skin can skew pH readings.

PERFORM TESTS QUICKLY, before the sample has time to change temperature. Temperature plays a big role in water balance, and you want to test the sample while it’s still the same temperature as the rest of the water in your spa.

TO GET AN ACCURATE READ ON COLOR-BASED TESTS, don’t wear sunglasses, and perform the test in natural daylight. Some experts recommend having the sun behind you, holding the test vial at eye level, and holding a piece of white paper at a 45-degree angle behind the test vial to reflect light through it so that you can see the color clearly.

When squeezing drops of liquid reagents from a bottle,

hold the bottle in a vertical position so that the drops are uniform in size.

Make SURE REAGENTS AND TEST STRIPS ARE FRESH. Some experts recommend replacing reagents and test strips annually. To keep supplies fresh, close bottles of reagents and boxes of test strips as soon as you’re finished with them. Make sure your fingers are dry before reaching into a bottle of test strips. And store supplies in a cool, dry place out of sunlight.

Don’t TRY TO SUBSTITUTE REAGENTS from one test kit with another. The color standards, sample sizes, and reagent concentration may differ between one kit and another.

Follow THE INSTRUCTIONS on product labels carefully. If a test calls for the sample to be swirled, don’t shake it. Shaking could expose the water to oxygen or carbon dioxide, which could skew results. Also, watch the clock. Some test strips are designed to be read immediately, while others call for a waiting period. Waiting too long or reading too soon will not yield an accurate water analysis.

Note: Working with certain acid products can be particularly hazardous. For safety guidelines, see Chemical Safety, page 49.


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