Ok guys here is the latest. I added a gallon of cya to my 26k gallon pool three days ago. I tested today. My fc went from 1.0 to 3.5! I didnt add any liquid chlorine but did a boost on my swg to run at 100 percent due to some rain. I only added a gallon of cya as someone here said slow and steady with chemicals as some are hard to reverse. The cya didnt even register on the test. Everyone is going to tell me tonadd more right or else i will see my fc levels drop, right? My gut is telling me to wait a bit and test frequently. Once i see fc drop then add more cya. I am guessing what happened is the chlorine generated by my swg stuck a little longer with the cya and therefore didnt have tol add chlorine?
Love to hear everyones thoughts as i learn my new pool!
You're getting there. And by there, I mean knowledge. Your guess was a good one. You're learning.
The main point of the pool chemistry is to keep the water sanitized. Meaning taking care of all the organics you and nature put in the pool before they turn into microbes which cloud your water and make it turn nasty colors. The sanitization is taken care of by Chlorine. That's why you're measuring FC - free chlorine, or chlorine that's available to sanitize the pool.
Now, the salt water generator is taking the salt in your pool and turning it into chlorine through an electro-chemical reaction. Throughout the day, the chlorine will get "used up" and turn back into salt, which is then turned back into chlorine by the SWG. The SWG is not necessary for sanitization. You can simply add chlorine by adding bleach, pucks, etc. and accomplish the same thing. It is convenient, however, to generate your own chlorine from salt in an (almost, but not quite) endless cycle.
CYA is a stabilizer. It slows the "consumption" of the chlorine by the pool. That allows you to not have to add so much chlorine to the pool. If you were using bleach, that means less bottles of bleach. If you're using the SWG, that means running the pump less, or turning the % down lower. You want your CYA to be higher with the salt, so the salt cell isn't working so hard.
http://www.troublefreepool.com/content/138-water-balance-for-swg-saltwater-chlorine-generator
Now, personally, I would be worried that your FC has been so long for so long. The fact that you can't get your FC to stay up could mean several things. It could mean your SWG settings are off, it could mean that your CYA is indeed too low, or it could mean you are fighting a low grade algae outbreak...which is likely considering your pool didn't have much chlorine in it. You need to get your pool balanced so you can see what it does.
I would adjust your FC using BLEACH. Don't try to work it with the SWG, it's too hard to dial in, IMO. Take an evening when the sun is low and the swg is off. Test the water, and add some bleach slowly using pool math as a guide, until you get your FC to 5.0. Keep the pump on but the SWG off to mix, and mix using a brush as well. Take a reading before you go to bed.
Take a reading in the morning. You are performing an Overnight Chlorine Loss Test (OCLT) which is used when you SLAM your pool to kill algae. Similar to the SLAM procedure, but you are doing it at normal level. If your overnight chlorine consumption is low, then go back to playing with your SWG and CYA levels until you can read the FC every evening and it's in the "good" range, suggested above. If it drops significantly (greater than 1) then you may have a problem. Bring the FC up with bleach again and see what happens. Test the next night. If you're still consuming chlorine, you may need to do a quick SLAM.
Keep at it, you're getting there.