Quote Originally Posted by lisak View Post
I have a 23,400 gallon IG pool with a vinyl liner. I put one of the anchored mesh covers on the pool last fall and have encountered a new set of problems to replace the ones that I fixed with the cover. First time I have ever opened to less than perfectly clear water. I have been battling algae. I keep shocking and scrubbing but after reading assume that I haven't kept the chlorine high enough for long enough. Today I put in 5 gallons of 12.5% liquid chlorine and have been scrubbing. Here are my numbers before adding all the chlorine:

FC 1.8
TC 1.8
CC 0
pH 7.4
Hardness 40
Alkalinity 70
CYA 30

The pool store wants raise my alkalinity but from what I have read on here, I am thinking it is ok? I have already told them I am not adding calcium as I see no need for it in my pool. If I do need to raise my alkalinity, how much baking soda should I add? The pool store lady also wants to test my phosphate levels after I kill all the algae and then add a decreaser? I have never even heard of that. Since it doesn't fit the 3B's that I tend to use, I'm assuming she just wants money? What is she talking about and is that really something I need to do? I'll retest and repost in the morning. Also I seem to remember a chlorine calculator on here from a couple years ago to figure out how much to add, but I couldn't find it when I did a search. Does anyone have a link? Thanks for any help.

Lisa
Your numbers are FINE--don't mess with ANYTHING but chlorine. Your job now is to kill your algae so it stops eating your chlorine.
pH 7.4--PERFECT--Don't mess with it!
CYA 30--PERFECT--Don't mess with it!
CH 40--Anything below 500 is FINE for vinyl--Calcium does NOTHING for vinyl--it's a waste of money to increase it. It will have NO effect on your algae problem. --Don't mess with it!
T/A 70--MAYBE a tad low but that could be measuring margin of error. Unless your pH is jumping around, Don't Mess with it! If you MUST, add 1lb of Arm&Hammer Baking Soda (yeah, baking soda) and no more.

What you need is to get your FC up to 12 to 15ppm and that's going to take lots of LC. One gallon of that 12.5% LC will add about 6ppm to your pool. So add 2 gallons and then, 8 hours later, measure your FC and add LC to get it up again. Do this 3x a day to maintain the 12-15ppm level until your FC and TC are the same (which means CC is 0--what you want) and FC doesn't drop so precipitously.

Basic algae fighting drill...check our stickies.

But don't add anything but chlorine to your pool.