Question about shocking the pool

[Dooley11]

This should probably go in the chlorine forum but it is showing private for me. I have not shocked my pool before. (new pool) So I have a question. I have a cya of 30. I know I need my FC at 15 ppm to shock. So if I do this in the evening, at what point should we be able to swim again?

[Watermom]

It is actually ok to swim at shock level, just wear old suits.

Why do you need to shock? It is only necessary to shock if your chlorine drops too low for your CYA level (per the Best Guess chart in my signature below) or if you have a CC reading greater than 0.5ppm or if your water is cloudy. It is not necessary to shock weekly or on any kind of schedule. Some summers I never shock my pool at all.

[Dooley11]

Excellent answer, Watermom! I honestly don't know why I need to shock other than that's what I thought you had to do from time to time.

[johninmartinez]

Watermom, as another newbie I could use an explanation or two of the Best Guess chart.

first, what are the two columns labelled "shock"? (meaning, what is the difference between the two)?

second, could you explain why the very high FC levels would call for shocking with more chlorine? This doesn't make sense to me, but then again I'm new, so very little pool stuff makes sense to me just yet.

Thanks in advance for any insight you can provide.

[waterbear]

Watermom, as another newbie I could use an explanation or two of the Best Guess chart.
I'm not Watermom (I'm prettier) but perhaps I could help explain it.
first, what are the two columns labelled "shock"? (meaning, what is the difference between the two)?
The first column is normal shock levels when there is combined chlorine above .5 ppm on testing or at the first signs of cloudiness or after heavy rains or heavy pool usage.
The second column, shock+, is how high you need to take the chloirne for fighting mustard algae or black algae or if there is an ammonia problem in the pool.
second, could you explain why the very high FC levels would call for shocking with more chlorine? This doesn't make sense to me, but then again I'm new, so very little pool stuff makes sense to me just yet.
It's not the high FC levels, it is the level of CYA (stabilizer) that determines how high you need to keep the FC for normal chlorination and for shocking. Basically, the higher the CYA the more the chlorine is chemically attached to the CYA (as chlorinated isocyanurates) so you need higher chlorine levels to provide the same amount of chemically 'unbound' active chlorine in the water to compensate.The amount of "active' chloirne is basically the same in all cases
Thanks in advance for any insight you can provide.

Hope this helps.

[Watermom]

WB wrote --- "I'm not Watermom. I'm prettier."

WB -- Oh yeah??

[waterbear]

wb wrote --- "i'm not watermom. I'm prettier."

wb -- oh yeah??

roflmao! I DID roll my eyes!

[CarlD]

WB wrote --- "I'm not Watermom. I'm prettier."

WB -- Oh yeah??

Yeah, I'm with you, Lisa. I have real trouble visualizing it, too! (Isn't that when Moe whacks Curly over the head?)