Dichlor and free chlorine levels

[matt_s]

I have a spa with Ozon and Nature 2, approx. 500 gallons in it. I have been giving instructions to:

1. After each use, add 1 teaspoon dichlor per person. So, three people makes 1 tablespoon. Last time it took at least six hours to get the levels down to 3 ppm. Intially it was at 10ppm.

2. Each week chock with 2-3 tablespoons. Last time, I had 10 ppm free chlorine 12 hours after (before chock 0.5 ppm) So, lets say 24h until useable again.

To minimize the  downtime for the spa would it be possible to do routine 1 on the evening dependless of how many times/people have used it during the day? That way you could let the chlorine levels go down during the night. Because if you really go with after each use, the spa is useless after the first use.

[chem geek]

1 tablespoon in 500 gallons would increase the FC by 4.2 ppm.  So if it got to 10 ppm that implies that you started out your soak with 6 ppm.  It sounds like you've been using too much chlorine.  Your ozonator will oxidize bather waste so if you use the spa regularly (i.e. every day or two) then you won't need to use as much chlorine.  Also, if you consistently maintain the chlorine level throughout the week, you shouldn't need to shock.

You could, instead, just add enough chlorine after your soak so that you start your next soak with 1-2 ppm (or more, if you don't mind a chlorine smell during the soak, but most people prefer to not have as much chlorine during the soak).

[matt_s]

No, I measured before..it was around 0,5 ppm. I have a Lamotte dipcell so it is not an exaxt reading but it was not above 1 ppm. Maybe I measured too soon after I poored it in, but I kept the jets running a couple of minutes and then waited 15 minutes before the next measure. The product I'm using says 100% dichlor.

[Chas]

I usually tell my customers to wait eight hours to re-test pH, TA or Chlorine.