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Water Testing FAQ
What chemical levels do I
need to test for regularly?
The four main tests to perform with a
test kit are
pH,
chlorine (or other
sanitizer residual),
Total Alkalinity
and
Calcium Hardness.
Cyanuric Acid
levels, mineral content, Total Dissolved
Solids and
Acid or
Base Demand tests may
also be performed as needed.
How often
do I need to test the water?
I
should say everyday, but I realize
that's a bit much for most people.
Commercial pools are required to check
chlorine levels every hour and record
their findings in a log, however the
"backyard lifeguards" should check their
pH and chlorine levels at least 2-3
times a week. Chlorine should be fed
continuously through a
feeder device to
maintain a consistent level. Total
Alkalinity and Calcium Hardness levels
tend to fluctuate less, so weekly
testing should be O.K.
What are the recommended
levels?
-
pH: 7.2 - 7.8
-
Chlorine: 1.0 - 2.0 ppm
-
Total Alkalinity: 80 - 120 ppm
-
Calcium Hardness: 180 - 220 ppm, though some
say 200 - 400.
-
Cyanuric Acid: 25 - 50 ppm
-
Total Dissolved Solids: 500 - 5000 ppm
How long
do my reagents last?
Typically one season.
Reagents lose
their strength over time and can also be
ruined by direct sunlight and
temperature extremes. Replace your
reagents annually.
Can I use reagents from
other test kits with my test kit?
No; drop size, concentration and color
variation will provide inaccurate
results.
Can I use a chlorine test kit for
bromine?
If you have a
DPD test kit, you need simply
multiply the test result by 2.25 to obtain the bromine equivalency. This works because
bromine is over twice as dense as chlorine.
My test kit shows no
Chlorine, even though I know it's
there...
If chlorine levels are excessively high,
the content can bleach out DPD, a reagent commonly used for chlorine testing. Either dilute
the sample with chlorine free water, or double the # of drops of DPD, and multiply or
divide accordingly.
There has been evidence that excessively high levels
of stabilizer, or
cyanuric acid, can cause a phenomenon called chlorine lock. Levels above
100ppm of cyanuric acid (CYA) may prevent chlorine from registering and possibly
sanitizing. Lower CYA levels by dilution.
If you smell chlorine in the water, you are very
possibly aware of combined chlorine, known as chloramines. These will not register in a
test for free chlorine. A good DPD test kit will allow you to test for total chlorine
levels and free chlorine levels; the difference being the combined levels. If trace
amounts of combined chlorine is above .3 ppm, you may need to
shock the pool to break the
bond of chloramines; this shock level is around 30 ppm.
When I test for pH, I get
a purple color...
If
your reagents are in good condition, a
purple color in a pH test is an
indication of chlorine levels being too
high and interfering with the test. Add
a drop of thiosulfate reagent to remove
the chlorine from a new sample, and test
again.
What type of test kit do
I need?
There are many different types of
test kits commercially available. If you are
concerned about
water balance, (and you
should be) you will want to spend more
for a nice kit. The basic "duo" test
kits, available for about five bucks,
are usually OTO chlorine and pH testers only. You may wish to spend more
for a DPD chlorine kit, which measures free, combined and total chlorine levels (OTO
measures only free levels). Also important is the ability to test total alkalinity and
calcium hardness. Acid demand and base demand tests will allow you to perform a
titration
test on your pH sample. Simply count the # of drops to determine, with the help of a
chart, exactly how much acid or base is needed to adjust the pH. A "four-way"
test kit will test pH, chlorine, alkalinity and acid demand. Test strips are available now
with "Litmus test" technology. These are "dip & read" strips of
paper that turn colors indicating levels of pH, alkalinity and chlorine in the pool.
Fairly simple to use, however, it seems that they may not be quite as accurate. Your pool
professional can check the water for metal presence, cyanuric acid levels and TDS (total
dissolved solids). If you have a
biguanide
water treatment system or a chlorine generator, you'll obtain special test kits from these
dealers. |
