Help with chlorine amounts

[plucky71]

Hello,
I am planning on shocking my pool today. It has been unused and uncovered for at least four years. I have all of the debris out of it. It actually doesn't look that bad right now compared to a week ago. Anyway, I added cya and got the level up. Now I want to start adding chlorine and would like to have someone double check my math. Can anyone take a look and let me know if I'm correct?

FC 0
CC 0
ph 7.2
t/a 50
ch 130
cya 50

I think my target shock level is 20? So with 12.5% bleach I need to add 239 oz. Thank you for the help in advance.

 

[JasonLion]

Yes, that all sounds correct. In round numbers you need almost 2 gallons of 12.5% to go from zero to 20.

 

[plucky71]

Thank you. I just found out something else. The Pool Calc says my target shock level is 16 but the tfp chart recommends 20 for cya of 50. Any thoughts on that?

 

[duraleigh]

Shocking the pool is a process, not a one-time event. When you add enough FC to get to 20, it will rapidly deplete that FC (perhaps in hours) and you will need to continually test and add more to keep it up at 20. The shock process can last a few days so be prepared for much, much more chlorine than your initial dose.

To understand this better, read "How to Shock Your Pool" up in Pool School.

 

[plucky71]

Thank you. I actually have lots of chlorine, I was just wondering if I should target 16 or 20 or does it not really matter?

 

[duraleigh]

It's not overly critical but i certainly would suggest 20

 

[Bama Rambler]

Thank you. I just found out something else. The Pool Calc says my target shock level is 16 but the tfp chart recommends 20 for cya of 50. Any thoughts on that?

There's a little difference in the recommended shock level between the pool calc and the FC/CYA chart at higher CYA levels. Either is ok to use and will get the job done. The Charts suggestion will get it done a little faster at the expense of a little more bleach.

 

[plucky71]

Thank you all for your help. I added 2 gallons 12.5 and after 45 minutes my FC is at 28. I vacuumed during that time so now I'm going to start brushing. So far so good. I'm a little nervous as a first timer.