Best guess question

[dansdad]

I see the best guess but I am trying to properly read it.
1. I have a cl. reading of 3 which tonight I will raise with bottled chlorine
so I understand the min. 3, max. 6 but the shock 15 and +shock+ 30 , what is that? don't know what it means. Please advise, Dave

[chem geek]

"shock" is when you have a problem such as algae or some higher than normal chlorine demand (especially overnight). +shock+ is when you have yellow/mustard algae since that is harder to kill.

[dansdad]

Ok now since 15 is for green and 30 is for mustard is that saying double the shock?

[Themadczar]

It's saying that's the level of chlorine to maintain in your pool... If you are at 10ppm now, you need to add 5 to get to 15 or add 20 to get to 30ppm. So it is double the level of fc but you do not necessarily double the amount of chlorine you add.