photo courtesy AquaChek
When a homeowner or service tech gets a wonky reading on a water test, it's easy to assume one of two things: the water chemistry has gotten way out of whack or the equipment is faulty. While these things do happen, it's more likely the tester that's to blame.
More-experienced water testing professionals may feel they're the exception to that rule, and that their time-tested methods ensure accuracy and consistency. But whether it's a homeowner dipping her first strip or a CPO working his thousandth titration test, it pays to begin the process with a little humility. Take Claudio Azurmendi's lead. In his role as technical services analyst for chemical giant BioLab, Lawrenceville, Ga., Azurmendi makes it his business to test water carefully. If he has occasional lapses in technique ("I've caught myself holding reagent droppers at an angle in the field," he confesses.), then just about everyone could use a refresher on the fundamentals.
"If you want the best pool experience, then following proper technique and using good reagents or test strips is important," he says. "We just recently went over some basic techniques with our sales team, to give them a little refresher. There are always little things that you do without thinking. You may have been doing something wrong for 10 years without even being aware of it."
Here, then, are the top four ways to ensure accurate test results. Adhere to these principles and you'll avoid common pitfalls that can lead to balky readings and bad remedies.
1. Carefully collect and care for the water sample.
When approaching a 20,000-gallon pool to collect a testing sample, it's easy to fall into the trap of thinking that the water on one end is the same as the water on the other. Or, that the water near the surface is chemically identical to the water down deeper. Don't make this mistake.
"Before you even get to the testing, the sampling technique and sample handling are big factors," Azurmendi says. "You want to get a sample that's representative of the whole body of water so you're not taking in a sample that's higher or lower in chlorine, for example, than the rest of the pool."
So where is this water? You're not going to find it near the top step, nor are you likely to find it by randomly dipping a vial into the water. Your best bet, experts say, is at least a foot deep, midway between the shallow and deep end, away from return lines and skimmers. In addition, if the water's been treated recently, make sure it's turned over a couple of times.
This water should be collected in a clean vessel that's been rinsed with the water you're about to collect. The goal here is to avoid cross contamination.
"Use a clean plastic bottle. Insert it bottom-side up so the trapped air keeps out the water momentarily," says Patricia Fitzgerald, vice president of marketing for Sparks, Md.-based Taylor Technologies. "Turn the bottle rightside up when you get to elbow depth and let it fill."
The collection technique is the same whether you're collecting for a reagent test or you plan to take a reading with test strips. In either case, on-site testing ensures that the water you collect has the same makeup as the water you test. Often, though, samples are brought back to a retail store or service center for analysis there. In that case, careful handling is your ally against the enemies of excessive heat and passing time.
"This is something that gets botched a lot," says Joe Sweazy, national sales manager, AquaChek Pool and Spa Test Strips, based in Elkhard, Ind. "The water sample is a smaller volume of water, and as such it has a tendency to change more rapidly than the huge pool.
Sweazy hears about people collecting the sample correctly, then tripping up and affecting the test by tossing the bottle into the back of a truck or onto the passenger seat of a car and driving around on errands. The results of this carelessness, according to Sweazy, are significantly altered and therefore unreliable test results. The sanitizer level is particularly apt to drop over time.
2. Use only as directed.
After a sample has been collected and transported with forensic precision and attention to detail, mistakes can still be unwittingly made by even the best of service techs when it comes to using the testing products. The problem? They simply fail to follow directions. Homeowners, needless to say, are a good deal more likely to drop the ball at this stage.
"The big thing we always try to reiterate to our customers is to read the instructions," Sweazy says. "It's simple, and obvious, but that's what leads to the majority of complaints we hear."
Sometimes a tester switches from Brand A test strips to Brand B, but fails to account for differences in testing procedures. One test may call for a quick dip, another a slow swirl. These instructions aren't made up by creative copywriters, but rather by scientists who prescribe specific steps based on the chemistry of the strips. There simply isn't one right way to perform a water test, and to perform one after another, possibly switching brands or getting careless with procedures is to invite inaccurate results.
Liquid reagent tests require precise timing, too. Fitzgerald cautions that copper, iron, manganese and nitrate tests often need a little extra time for proper color development. That's why the instructions call for the results to be read in a certain order — as those at the end of the sequence require the longest reaction time.
"Even if it is the same test equipment from the same manufacturer, something important in the procedure may have changed since you last bought it," Fitzgerald cautions. "The takeaway here is that if a 'simple' test strip has a required technique for successful use, you can bet the farm all your other testing supplies do, too. Stay informed by reviewing the instructions."
In addition, it should be pointed out that tests don't last indefinitely (replace them at least once a year, Sweazy advises), dirty or broken equipment isn't reliable and there are specific care instructions for the different types of tests. Thankfully, manufacturers are good at spelling all this out in the instructions. Make sure to read them whenever you buy a new set.
3. Be careful with color and light.
"Doing color matching tests in artificial light, or with your sunglasses on, is a no-no," Fitzgerald says. Tests are meant to be read in natural light, but if you must do it indoors, consider a portable daylight simulator.
Even given ideal conditions, there are factors that can interfere with accurate readings. Some people have what's known as low color discrimination, and as a result will have trouble matching color blocks.
"Even those with average or above-average discrimination can make mistakes from time to time," Sweazy says. "So it's important to know the trends of your water, and so when something doesn't look right, maybe it's got to do with your color matching, and maybe it's time to take another test."
Even in-store testing stations aren't foolproof color matching machines if not used properly.
"With our systems, you need to start the time on the computer at the same time that you dip the test strip so that the instrument knows exactly when it's supposed to read the color blocks," says Sweazy. "If you dip the strip and then put the strip on the tray, and that takes five or six seconds, and then you start the timer? Unfortunately you've already lost those few second of color development, so it's going to be past the prime time to get the appropriate test result."
4. Clear-up chemical interference.
Let's now assume there's been a clean chain of custody for the water sample. The water was properly procured in a clean plastic container, it was kept out of the sun and either tested immediately or taken straight to the store, and all equipment was used in strict accordance with the manufacturer's instructions. What could possibly go wrong now? Plenty, according to Fitzgerald.
"There could be interferences in the water that cause the wrong color to develop, or color not to develop," Fitzgerald says, citing examples such as a high level of sanitizer, the presence of monopersulfate-based oxidizer, copper from an algaecide or iron from fill water.
Here's a common problem: chlorine that exceeds 10 ppm or bromine over 20 ppm can bleach the pink color of a conventional DPD color-matching sanitizer test, and can cause the pH and total alkalinity tests in both liquid kits and test strips to give false readings.
"Generally speaking, if a tester gets odd results, it's important to be aware that there are ranges for all of these tests," BioLab's Azurmendi says, "and that if the sample is out of range for any one parameter, most often for chlorine and bromine, you should remember to retest and look for things like a high chlorine residual or pH.
"It's really common to not understand the limitations of the test you're using. You need to know that if you have an excessive level in one parameter, you might want to retest the water once you've got that parameter under control."
Final examination
In the end, you should keep in mind collection, care, strict adherence to prescribed protocol and a good working knowledge of pool chemistry are all important factors in keeping pool water clean. Failure in any one of these areas can foul up test results and lead to frustration, or worse, unnecessary chemical remedies to problems that may not even exist.
"It's really important to us that the people who are using our products are getting accurate test results," says Sweazy. "We are more than willing to help if people have problems. We're a good source of information, and can help with troubleshooting."
Taylor, BioLab and the other chemical manufacturers offer similar help on websites, through toll-free numbers and, of course, on the printed instructions that are too often discarded by the user.
Comments or thoughts on this article? Please e-mail barrett@aquamagazine.com.
Barrett Kilmer, has been on the editorial staff of AQUA magazine since 2000. He has a B.A. in English from the University of Wisconsin - Madison, and currently lives in Madison, Wisc.
