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
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.