Swimming pool test kits.

One of the most interesting activities in which sanitarians may be involved is the inspection of swimming pools. This activity is fraught with perils: On their first swimming pool assignments, youthful enthusiastic sanitarians often eagerly - and quite literally - throw themselves into their work. We both seem to recall that, at least once a year, while testing the shallow or deep end of a swimming pool, some sanitarian has lost balance and become totally immersed in the vocation. Of course, the sample has to be voided and retaken.

Pool testing to ensure proper sanitation is absolutely vital in minimizing disease risk. All water activity venues must be tested - not only public wading and swimming pools, but also hot tubs, medical treatment pools, ceremonial pools, spas, whirlpools, and water parks. Evaluating these facilities for environmental health compliance includes checking the circulation, filtration, and water treatment records; the ancillary safety equipment; diving boards; ladders; and, most importantly, the quality of the water. Microbiological sampling often follows a negative test for residual disinfecting agents such as chlorine or bromine. Additional evaluations related to water cleanliness need to be performed, including evaluations of pH, total alkalinity, and chlorine stabilizer. It goes without saying that for a pool to be safe for bathing, water chemistry, temperature, and turbidity, as well as mechanical systems and deck equipment, must be properly maintained. Balancing the chemical parameters is also important; factors such as water hardness can affect the life expectancy of pool equipment such as ladders (through corrosion or scaling), and decaying equipment can, in turn, affect safety.

We have found several portable test kits on the market that allow for the testing of the basic parameters such as pH and residual disinfectant loading. More complete test kits measure pH, disinfectant residuals (chlorine and bromine), total alkalinity, calcium hardness, acid demand, base demand, and cyanuric acid. These expanded kits have a definite advantage in monitoring overall water quality.

Test kits use one of two methods to assess residual chlorine levels in swimming pool waters: the orthotolidine (OT) method or the N,N-diethyl-P-phenylenediamine (DPD) method. With the OT method, the chlorine residual is indicated by a yellow color, but the shade of yellow that indicates free chlorine is very fleeting, and the end point is a darker color that represents total (free and spent) chlorine. Most people cannot distinguish free chlorine with this test. Also, OT is a carcinogen. DPD tests indicate chlorine with a characteristic pink color and more reliably distinguish free chlorine (the active sanitizer) from total chlorine (which includes spent sanitizer). For this reason, most health codes specify DPD testing.

Some kits use liquid reagents that are added to the water sample. Others use powdered reagents that are packaged in vials, small plastic pillows, or as tablets. These reagents are added to the water sample to yield a reading. In colorimetric tests, the developed color is matched to a set of color standards to make the reading. In titrations ("drop tests"), the reading is taken at the point the sample color changes to another distinct color. The main piece of equipment in test kits such as the Taylor Technologies(*) and Guardex(**) kits is the "comparator block," which holds the samples and comes with printed or liquid color standards. More sophisticated models, such as the HACH DR 100 Colorimeter Swimming Pool Test Kit,(***) use a portable battery-powered electronic colorimeter to measure the various concentrations being tested. In our opinion, unless there is a compelling reason for buying the more expensive electronic colorimeter - such as problems with color acuity perception - the kits that rely on visual color comparison are adequate for most testing purposes.

Some basic considerations apply in the use of any pool test kit. First, a representative sample must be taken. This requires that samples be drawn from at least 18 inches below the surface of the water and away from return lines. This is the dangerous part of our work. To reduce the risk of total personal immersion, consider purchasing a liquid sample bailer - available from companies such as Nasco and Forestry Suppliers, to name just a couple. Ensure that all collected samples are representative of the water being tested. This is accomplished by testing at each end of the pool or at mid-pool. (Readings that differ significantly from one end of a pool to the other indicate that circulation may be inadequate.) Also make sure that the testing vials have been properly flushed between uses to avoid carryover of chemical reagents or water from the previous test.

Second, reagents deteriorate over time. The shelf life of all reagents is finite. Outdated test reagents can produce false readings. Other factors that affect the stability of the reagents include humidity, heat, light, fluctuating storage temperatures, and exposure to treatment chemicals. Keeping the bottles or vials tightly capped will help prolong the usefulness of the reagents. Some kits provide reagent stability data and recommend replacement times, perhaps every 12 months. Sure signs that liquid reagents have outlived their usefulness include fading of color or cloudiness of the solution, deposition of precipitates at the bottom of the vial, or salting around the cap. When any of these conditions is seen, it is a good idea to change the solutions.

Another issue is the stability of the desired end point color as it relates to the concentrations of the parameters being tested. If a color develops for only a very short period of time, you may miss it. The color may fade, bleach out, or darken, giving you erroneous readings. Also, be aware that one parameter being tested may interfere with the color development of another test parameter. For instance, too much chlorine in the water may give a false total-alkalinity reading. Remember, the less interference there is and the more stable the end point, the better the chance of a correct reading. A reputable manufacturer and familiarity with the written guidelines that accompany the kit are your best defense.

Make sure you check the test kits and the reagents before taking them into the field; do not rely solely on the records that accompany the kit. Replace missing, broken, stained, or torn components. It is also wise to run a complete "trial" test prior to actual use; standard solutions should be used in place of water samples in such a trial to determine that the test kit functions properly. Third, it is most important to follow the instructions that come with the test kit. Test cells and re-agents are not interchangeable, and improvisation will lead to erroneous readings.

Finally, the National Spa and Pool Institute (NSPI), sets forth some recommended water parameters for commercial and residential pools, spas, and hot tubs. State public health regulations may differ from these industry standards. Therefore, consult your local or state health agency for code requirements, recommended parameters, and the testing method that should be used. Some public health agencies actually specify the type of test kit that must be used to meet regulations. For instance, health agencies frequently require the use of the DPD method for chlorine testing.

While several swimming pool test kits on the market today do a very good job of testing the water parameters required by the sanitary codes and regulations of various jurisdictions, some are easter to read than others; some are easier to manipulate, some are chemically more stable, and for some, it is easier to get replacement parts and reagents. The prices of the kits vary according to the number of parameters they can test and whether the readings are done electronically or depend on simple visual detection. Study the marketplace for the best selection, and remember to have fun and stay dry.

* Taylor Technologies, Inc. 31 Loveton Circle Sparks, MD 21152 (800) TEST KIT (800) 959-SWIM

** Bio-Lab, Inc. Technical Solutions 627 E. College Ave. Decatur, GA 30030

*** HACH Company P.O. Box 389 Loveland, CO 80539 [phone] e percentage