Vacation Strategy

[chem geek]

I'm still a bit confused as to what the HOCl (ppm Cl2) label at the top of the chart means.

The "HOCl (ppm Cl2)" is the concentration of hypochlorous acid, what I've been calling "disinfecting chlorine", and the "ppm Cl2" just says that all chlorine measurements are measured in part-per-million as weight of chlorine gas (that's just the convention).

With no CYA and at a pH of 7.5, the Free Chlorine (FC) concentration is double the disinfecting chlorine (hypochlorous acid) concentration because the FC (with no CYA) measures both the hypochlorous acid (HOCl) and the hypochlorite ion (OCl-) and these are roughly equal in concentration at a pH of 7.5. So that's why I doubled the disinfecting chlorine (hypochlorous acid) concentration to get the FC level when there was no CYA.

Richard

[KurtV]

Got it; thanks.

[adesalvo]

Well I am back from a wonderful 10 day vacation. I had somebody add 1.4 gal of 6% bleach Sun/Tues/Thurs. I do not use a pool cover. I turned off the heater.

I left on a Friday morning with the following numbers..

FC = 10
CC = 0
pH = 7.4 - 7.6
TA = 100
CYA = 30
Temp = 86

Returned on the following Saturday night to a perfectly clear pool...sparking actually

FC = 8
CC = 0
pH = 7.8 to 8.0
CYA = 30
Temp = 105 the temp was set at 110!!

Fortunately the person adding bleach noticed the pool was getting low and added some water.

We are still in the investigating stages...but have a few leads...

[CarlD]

Sounds like your strategy was a success! Congratulations!