several important points to consider in using this chart.
First: The levels above assume that you are testing water from
a well-circulated pool, with a decent flow distribution. Most home pools
with pumps running on high meet this requirement. But if your pump has
been off, or if you are testing water from a typical suburban community
pool, you need to collect several samples and test them.
Second: While this is -- to the best of my knowledge --
a 'no-harm' chart to people, the no-harm applies to naked people with
normal skin. People with sensitive skin may experience significant skin
irritation at the higher chlorine levels, and swim suits containing
Lycra will be damaged. Also, people with dyed or treated hair are MUCH
more likely to experience adverse effects And while all polyester or
nylon suits may not be damaged physically, they are likely to be
bleached. All these effects, except maybe those to sensitive skin, are
time based. A brief dip in a pool at FC=50 and CYA=60 probably won't
lighten undyed hair, but a user swimming laps daily probably will see
Third: many of the chemical levels shown here are difficult to field test. Even with DPD-FAS, chlorine levels above 50 ppm are
hard to measure, and it's easy to screw up testing. CYA levels below 20 or above
100 are also difficult to measure with the kits available to pool
users. There are some clumsy work-arounds, but they are not ideal. SO, for some levels, testing has to be replaced by 'dead reckoning'. I
can't test for 5 ppm of stabilizer, but if I add 5# to the skimmer of a freshly
filled 120,000 gallon community pool, with a freshly backwashed sand filter, I
can pretty much 'reckon' on 5 ppm of CYA when I return a day later.