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Direct
Pool Supplies
What testing method should
you use?
You don’t have to be a chemist to keep your pool
sparkling clean. To keep things simple, use a testing
method that you find fast, easy and convenient. That way
you’ll be more likely to stick to your testing regimen.
There are two basic types of testing method used by most
consumers: test strips and liquid kits.
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Liquid kits require that you put a sample
of water into a plastic comparator and then
carefully add drops of chemical reagent, watching
for a change in the colour of the sample. Liquid
kits with the reagent OTO were once widely used to
measure chlorine, but they have fallen out of favour
in recent years. OTO measures only total chlorine,
not free chlorine, which is the form of chlorine
most effective in sanitizing your pool. In addition,
we now know that the chemical reagent in the OTO-type
kit can cause cancer.
Kits using the liquid reagent known as DPD do
measure free chlorine. However, if you test for free
chlorine using a DPD #1 liquid test kit, be aware
that high levels of combined chlorine, or
chloramines, can cause false-positive results when
testing free chlorine. Substances such as
monopersulfate (used for shock-treating pools) can
also affect the results of the DPD test by causing a
false positive reading. Moreover, the DPD test
requires careful technique and several steps to get
the best results.
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Test strips, the easiest method for pool
and spa water testing, are fast and simple to use
because they eliminate the need to measure samples
and count drops. Typically, you simply dip a strip
in the water for one second and then remove it. You
then compare the colour on the strip to the colour
chart on the label.
Industry and water quality experts report that test
strips are comparable in accuracy to liquid kits. In
fact, many believe they actually deliver greater
accuracy than liquid kits because they require
less technique. Many local and state health
departments now recognize test strips as an
approved testing method. This means that
professional pool and spa service technicians as
well as other industry experts trust the accuracy of
pool and spa test strips. Today there are reliable
test strips available to test a wide variety of pool
conditions, including cyanuric acid and total
dissolved solids as well as free chlorine, pH and
total alkalinity.
No matter what type of test kit you decide to use, be
sure to follow the manufacturer’s recommendations to get
the best results. |
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| Q: Why do my Test Strips read 0ppm for free
chlorine, while my DPD test shows a free chlorine reading?
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| A: If there is a high level of combined
chlorine in your pool or spa, it is likely the DPD test is showing a
false positive for free chlorine and your Test Strips are giving
an accurate reading. |
| Q: Do I need to test as frequently with test
strips? |
| A: Yes. We suggest testing both ends of
the pool a minimum of 2 times per week, and spas before each use |
| Q: Is DPD more accurate? |
| A: The DPD test for chlorine can be
affected by interferences, such as an over-abundance of monochloramines
or potassium monopersulfate (used for shock-treating pools). These can
give a false positive reading for free chlorine with the DPD chemistry.
Recognized technical studies are available to support these claims. In
addition, the DPD test requires careful technique and several steps to
get the best test |
| Q: How accurate are test strips?
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| A: Test strips are at minimum comparable
in accuracy to liquid colour comparator tests. Because test strips are
more convenient, we believe they actually deliver greater accuracy. They
reduce the chances of human error associated with liquid kits, which
require measuring samples and counting drops of reagent |
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