Drips, Strips & Everything In Between

Aq 605 55pg 0003Testing water is no day at the beach, but at least you can do it sitting in the sun next to a pool. Moreover, it's tremendously important to do it regularly - because no one wants a pool full of algae, stains or cloudy water. But what's the best way to test? To a degree, it's personal preference because for each type of test, there's usually at least a couple of ways to do it. To give you a better understanding of the available methods, following is an overview of what's on the market, how each method is often used and some tips for doing the various tests correctly.

Pick A Color

"In a colorimetric test," says Wayne Ivusich, sales manager for the pool and spa industry at Taylor Technologies, "reagents are added to a water sample where they react with the analyte of interest (e.g., bromine, free or total chlorine, copper, etc.) and produce a color proportional to its concentration. The color of the treated sample is then compared to color standards representing various concentrations until a match is made."

Colorimetric or color-matching tests are frequently used to test for chlorine and pH. In fact, the colorimetric DPD chlorine test is the one most health departments require for testing commercial and public facilities, says Joe Sweazy, technical sales and services manager for AquaChek Pool and Spa Test Strips.

Richard LaMotte, vice president of sales and marketing at LaMotte Co., notes that "the DPD method is an approved method not only in the pool industry, but also in the eyes of the EPA, but its downfall is when you get into high levels of chlorine. DPD is a very effective test between the area of 0 to 5 ppm, but when people get up into very high ranges, up around 9 or 10, you can get partial or complete bleaching of your color reaction. By bleaching out, I mean it goes clear.

Aq 605 55pg 0001 "And it's important that people understand that, because they'll think they don't have any chlorine in the pool, and, actually, they have a bit too much. So DPD is better used in the lower end of 0 to 5, and in the higher end, you're probably better off using a test strip because they don't bleach out."

When testing for pH, LaMotte says, " There's a very effective colorimetric method that's called phenol red, which is what everybody in the industry uses. The phenol red range is 6.8 to 8.4, so the one limitation of the phenol red is that if you're below 6.8, you really don't know it unless you get another test out. So the thing to do is use a wide-range strip that goes from 3 to 10. You would hope pools don't get there, but they do.

"Another thing to mention is that if customers get a bright purple color [with the phenol red pH test], that's a clear indication that there's way too much chlorine or bromine in the pool. Normally, it goes from yellow to orange to red, so a bright purple is a good indicator that something has gone wrong in the pool."

Overall, says Ivusich, color-matching tests are very easy to use and relatively inexpensive. "However, they require you to be able to differentiate between colors (often hues in the same range, such as the pinks of a DPD chlorine test, or the blues of a copper test). If you have trouble making color distinctions (and it's estimated that 6 to 8 percent of the population does, mainly men), you may have difficulty with certain colorimetric tests. And if you're testing indoors, you should use a special lamp that simulates daylight for best results."

If, for instance, you have trouble distinguishing between the shades of pink on a DPD color comparator, then don't use a DPD test for chlorine, says Ivusich. "Use an FAS-DPD drop-count titration instead, or let a colorimeter make the reading for you. Similarly, if you have colloidal color (say from metals) and/or turbidity in your water sample, be sure to select a test method that can compensate for it."

Drip Drip

Another widely used testing method is titration. To perform titrimetric tes ts , Sweazy say s, "You add a reagent and the sample will change color. Then you add another reagent drop by drop, counting the drops until it changes another color or it goes clear. So what you're looking for is an exact end point where you get a color change from one color to another in this titration, and as a result, the titrations can be more precise and not so subjective. You don't have to be a color expert to get a good result with the titration because you're previous color."

LaMotte says that because you can get such precise results with titrations, this is the testing method that has been used traditionally to determine alkalinity and hardness.

But while titrations are more precise than test strips, for example, t h e y're also more time consuming, according to Sweazy. "And they tend to be a little more expensive because you've got more than one reagent that you're using," he says.

Nevertheless, because of the precision they offer, titrations are still frequently used. "In the case of service profes sionals," says Sweazy, "what they're doing a lot of times is t h e y' re us ing the test st rip as a screening tool." And if they fi n d something is out of its ideal range, t h e y'll do a titration. Ivusich offers a specific example: " Suppose you're using a typical total alkalinity test strip (with printedcolor standards for 0, 40, 80, 120, 180 and 240 ppm) and you get a reading between 40 and 80 ppm. How much sodium bicarbonate should you add to increase the alkalinity to 100 ppm? The simple answer is: You don't know exactly.

"The test strip doesn't provide the resolution necessary to translate test results to treatment, and you will likely underdose or overdose. In this example, it would be better to use a drop-count test that can provide a total alkalinity reading in increments of 10 ppm, allowing you to more-accurately calculate the chemical dosage from a treatment table."

According to Sweazy, using some combination of methods when testing is really not too expensive in most cases. "Because if they're using strips as their primary method and they're backing up with liquids or they're using liquids as a primary method and backing up with strips, they're probably only doing that other method a handful of times in a weekly service route."

Quick And Easy

As Sweazy suggested, some service professionals today are using strips as more than just a screening tool - they're using them as their principal testing tool, because of their quickness and ease of use.

In fact, says LaMotte, "We know many service guys have converted to test strips and love them and use them religiously and have found that they're much more reliable than they were 10 years ago.

What often happens is the service guy might go out once a month with a five- or six-way strip, whereas for their daily, they'll use a four-way strip most of the time, which does free and total chlorine, pH and alkalinity." Pool owners, of course, prefer to use tests trips, says Sweazy, "because they're fast, easy and accurate. So they can get results and quickly make adjustments. The one setback with the strips is that they are not as precise as some of the other methods.

" Yet for the consumer, they're an excellent test because they'll give them an idea of what's going on in the water and whether they're OK or not, and the customer then is more likely to continue using test strips and test more frequently because it's easy to do and they don't have to spend a lot of time doing it." But if you give liquid kits to customers, continues Sweazy, they' r e probably not going to test as often because it's just not as easy for them to do. "So they might test once every other week or something like that, but if they've got test strips, they can just go out and dip in and say, 'Am I OK or not?' They're going to do that a lot more often."

And if pool owners do encounter a problem they don't know how to solve after testing with a strip, many then take a sample into a dealership that offers in-store testing, says Sweazy. Even though at this point strips are not often used to test public and commercial facilities because most health departments require other types of testing, LaMotte believes test strips can be useful in these facilities.

"My feeling is that public pools sooner or later are going to have to get on the bandwagon with test strips," he says. "They could use a test kit maybe in the morning and at night, when there is no one in the pool or they're closing up.

But during the day with a test strip, they can stick it in, check to make sure there's sanitizer and the pH is t h e y're done versus taking five minutes by the side of the pool and running a test while someone could be drowning."

Dot Or Not Dot?

A turbidimetric test is commonly used to measure the concentration of cyanuric acid (CYA) in pool and spa w a t e r. "In this analysis, which is based on view depth," says Ivusich, "you add reagents to a water sample and they react with the stabilizer present, causing a cloudy precipitate to develop. Then, you usually pour the prepared sample into a transparent test cell with a black dot printed on its bottom. You stop pouring when the black dot is obscured by the turbid sample. The CYA concentration is determined by comparing the liquid level in the cell with calibration marks on the side.

" Visual turbidimetric tests are quick and easy to use, and they eliminate the need for costly electronic turbidity meters. However, matching turbidity standards can be somewhat subjective since these tests may require you to estimate a reading between two values."

Those who don't care to use a turbidimetric test for CYA usually use a test strip instead.

The Digital Age

Yet another testing method available to pool and spa professionals is microprocessor- based instruments like strip scanners or hand-held electronic instruments that can be used to measure pH, temperature, total dissolved solids and oxidation-reduction potential. "These instruments analyze samples in the same way each and every time, providing consistent results," says Ivusich, "and the technology employed in colorimeters makes them far more sensitive to distinctions in color than the human eye.

However, they must be properly maintained and calibrated regularly, many aren't waterproof, they can be out of commission most inconveniently, and it can be difficult to justify their higher cost, particularly if one of the simpler wet chemistry methods provides acceptable accuracy."

Sweazy concurs: "Right now the biggest issue, quite honestly, is cost of those meters. They're fairly expensive and they might last one or two seasons. Pool water is pretty hard on some of these meters because of the chlorine and things like that." Plus, notes Sweazy, the average meter sustains a fair amount of wear and tear as it bounces around a service tech's truck while he travels his route.

Whatever method or combination of methods you choose, it's important to know the idiosyncrasies of that method because, says LaMotte, "A lot of water testing is a matter of getting a feel and familiarity with whatever you're using." So the more you understand your tests, the more time and money - perhaps your two most precious commodities - you'll save.

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