Quote Originally Posted by johninmartinez View Post
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.