Includes both instrument and operator variances. The greater the inaccuracy, the more difficult it is to keep water in balance.
SOURCE: PALINTEST Includes both instrument and operator variances. The greater the inaccuracy, the more difficult it is to keep water in balance.

Percentage of inaccuracy vs. ideal conditions

Maintaining a safe water balance can be a daunting task. And with the possibility of improper chemical levels causing extensive and costly damage to pool walls and equipment, water management is not a job to take lightly.

The basic principles behind water balance are not overly complex. However, there are nuances to water balance that do take time to understand and are only mastered after years of experience and lessons learned from making mistakes.

One way successful water balance can be achieved is through accurate and thorough testing of the water.  But even the most experienced and knowledgeable person with water chemistry is only as good as the accuracy of the test instrument being used. In recent years, a host of manufacturers have introduced testing equipment with claims of improved speed, reduced cost and pinpoint accuracy. Types of tests range from visual test strips and drop kits to recent introductions of digital strip readers and photometers that offer the most advanced and accurate data.

Each type of testing platform carries a different level of accuracy:

  • Test strips are produced from plastic strips with chemically impregnated pads on the ends which change color when reacting with specific ions. Matching the strip to the closest color on a color chart produces a concentration reading. While test strip manufacturing has improved in recent years, the results are still based on the interpretation of the person matching the strip to the color chart. Color blindness, age of the test strip, manufacturing quality and environmental conditions all play a role in the accuracy of the test strip reading.
  • Digital test strip readers are a relatively new introduction to the market. This technology takes some of the human element out of test strips and drop kit comparisons. After a test strip is dipped into a water sample for five seconds, it is placed into the digital reader where a comparison is automatically made through a color chart pre-loaded into the digital reader. This method eliminates the need for a color chart or comparator block. However, digital readers still use test strips with inherent inaccuracies related to age, manufacturing quality, environmental conditions and the accuracy of the digital reader itself.
  • Photometers are considered the most advanced and professional equipment for testing water quality. Measurements are based on the amount of light absorbed by a water sample with reagents added. Typical methods utilize a pill or liquid which is mixed with the pool sample. After zeroing the photometer, the sample is placed into a receptacle on the unit and a test button is pushed.  Results are displayed on a small LED screen in ppm or mg/l in a matter of a few seconds.
  • Drop, or liquid, tests require the user to fill a vial with the water to be tested. Then, a reagent is added and the resulting color of the sample is matched against a guide on the vial. In acid demand tests, the user counts the drops of reagent needed to reach a certain pH. 

    • When deciding on a testing platform, initial cost undoubtedly enters into the decision making process. Each testing method has its place. However, understanding the accuracy of each test and how accuracy can affect a facility’s operating cost is important. When testing for free chlorine, for example, a photometer can be 10 percent off the correct reading, while a liquid test can be 25 percent off and a test strip can be up to 50 percent off.  Not all inaccuracies are the result of instrument error, but encompass typical operator error as well. These variances can cause facility operators and pool owners to use the wrong amount of chemicals, which affects water quality and the bottom line in the form of unnecessary chemical purchases. 

    Based on average chemical costs, an operator of a 150,000-gallon pool could pay over $1,600 more per year in unnecessary costs trying to bring the water back to ideal conditions.  Further, the pool tech may continue to make additional adjustments to water balance utilizing an inaccurate test platform, pulling the balance further from ideal conditions and starting an endless cycle of adjustments. 

    Not included in the calculations of additional cost are those that result from improperly maintained water, such as corrosion, scaling and swimmer discomfort. When it comes to testing methods, many decisions are made based on one aspect of the testing method, such as time or cost, when in fact the bigger picture should be considered. Saving a few dollars up front could result in a higher cost of operation down the road. 

    There is a place for all test methods, each serves a purpose and each has a place it will work best. Testing methods should be researched and many factors should be considered when making a decision on which method to utilize. Frequency of use, durability, portability and of course cost should be factored in. Don’t buy on cost-per-test alone, buy on knowledge of the complete system and how that system can affect the entire facility.