Wonderful I'm glad it's looking good.
Yes pool math can take some getting use to but once you master it it will be smooth swimming. PM is the BOMB LOL
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1st make sure Your gallons of water in your pool are correct at the top. Put your current level in the 1st box, on the left outer side, and goal in the 2nd box, right inner side.
On the very top line Put what percent of chlorine you are using where it says percent, and what size jug you are using.
Then hit calculate.
Once you hit calculate if you will run your mouse cursor over the top line for the Liquid Bleach it will break down how much X amount of ounces is for you making it easier for you to judge it by the jug size and % you are using. That way you know how much to add to get from where you are to where you want to be.
You should be running a level that is equal for your CYA level per this chart.
http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock.
So if you are currently at 20 CYA which you said you may even be lower, but we will say 20 CYA for now.
According to the CYA chart you would only need 2ppm Min and 3 Target of Chlorine for your pool.
BUT having a 20 CYA is not a good. CYA see the * on the chart it is not recommended to keep it that low, so you will need to raise it to about 40CYA using Cyanuric Acid as described in comment #36.
and YES a CC of .5 or less is ideal.
So while your FC level is dropping get some Cyanuric Acid (I prefer the powder form myself) It will say Chlorine Stabilizer on the container and the ingredients will be 100% Cyanuric Acid.
To Calculate this yourself,
Make sure your gallons of water is correct at the top.
UNDER the Yellow CYA section of pool math put in 20 CYA as your current, and 40 as your target. Click Calculate
Run your mouse cursor over that section and the 1st line will tell you how much you need in powder form (remember this is to be put in a sock and hung over the pool in front of a return, Detail described in comment #36
The 2nd line will tell you how much is needed in liquid form (the proper amount of this can be poured into the water in front of a return and then Brush that area with your broom after.)
Use whichever line you need to depending on whether you are using powder of liquid form of CYA.
(By my calculations for YOUR water gallons, it is 41 ounces of the powder form, or 106 oz of the liquid form).
Did you get the same answer?
If using powder form it comes in 4 pound containers. 41 ounces is =2.56 pounds. ,so it will be just over 1/2 of the container, but it is best to measure closely and for now ADD JUST 2 POUNDS of CYA POWDER in a SOCK placed in front of your return. The CYA will help your chlorine hold better.
Recap:
Let FC drop to say around 6ppm, but no higher than 10ppm, until we get the CYA adjusted. This way it will still be safe to swim in at that level, and we are bringing your CYA up to met it at the higher level.
Add 2 POUNDS of powder Cya, or 106 oz of liquid stabilizer, to raise CYA from 20 to 40ppm (MEASURE Accurately) it is much easier to add more of this later, then to remove it back out.
Once those 2 things are done and we tweak whatever numbers need tweaking after that you should be in good shape.
I hope this helps.