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The higher you keep your cya, the higher you'll have to keep your chlorine level to keep it sanitized. That is what gets so many people in trouble. They continue to add cya via trichlor pucks and yet the pool store tells them to keep their chlorine level between 1 and 3. And, before you know it, they have a green pool and can't figure out why.
The higher the CYA, the more stable your chlorine will be. ***
BUT
CYA reduces the effectiveness of the chlorine as a sanitizer. This means you have to keep a higher level of chlorine if you keep a higher CYA.
If you have a CYA of 200, I don't even know how much Cl you would need on a daily basis, maybe 8-15, but to shock would take a ton... at 60-90ppm CYA (the highest level on Ben's chart) shock level is 20. Higher that 20 is not recommended for vinyl pools because of potential bleaching of your liner. And while swimmimg in a highly chlorinated pool is probably ok once in a while, I personally would not want to make a habit out of swimmimg in it!!
30-50 seems to be a number that keeps the chlorine relatively stable to sunlight, while not requiring HUGE chlorine ppm's to keep your pool sanitized.
***ETA probably only true to a certain point. I am not a chem. whiz...
I am so glad I found this site. They told me earlier today that my CY level was 90. Now I know that seem high however the way that they tested it was by putting my water in a little tube and lifting this rod until you see a little black ball. Now i saw them test it and the bube had marks on the side that had the 25 mark 50 mark and 100 mark. So how they came up with 90 is in my opion is only a guess.
Is that the same way you test it with bens?
You mix equal amounts of pool water and cya test reagent, then wait a minute or so. Then you slowly pour this mixture into a cylinder where there is a black dot on the bottom. As soon as you can no longer see the black dot, you take your reading from the numbers along the side of the cylinder. It is definitely the hardest of all the tests to read.
I would wait for Ben's test kit for your CYA level. Unless you are using a large amount of stabilized chlorine I can’t see 5lbs of CYA getting you to a level of 90 that fast. CYA is slow dissolving and can take a week to reach its full level. Since you poured your CYA in the skimmer I would also recommend you not back flushing your filter for a few days. The CYA will stick around in the filter while it dissolves.
The role CYA plays is kind of like sun screen for your chlorine. You go out in the sun you want to be protected but you still want a tan. Think of chlorine as your skin you want your skin exposed to the sun to get a tan but you don’t want it burnt. The CYA protects chlorine by bonding with it to protect if from the sun but we still need it to interact with the water. When chlorine hits water it forms other compounds that do the work of cleaning organics and killing the bad bugs. Like too much sunscreen too much CYA will not allow interaction of chlorine to the water in the pool.
I would be cautious of pool store results and wait until you get Bens kit to really dose your pool. You might go to Walmart and grab one of the 5 way test kits with liquid reagents while waiting. The CYA test seems to be a good one but be cautious about the TH. If you do get one of these kits remember some of the test are not accurate with a chlorine level above 5.
May I ask where at the pool are you getting your water for the test?
If you poured your CYA in the skimmer and getting the water at the return it may account for the incresed CYA level.
Steve
I am getting my water theoppisite side of the skimmer about 12 inches down. I guess my question is this. If the side of the tube goes from 50 to 100, how did she come up with 90? An educated guess maybe?
Guestimate....
Wait a week - you can get the 6-way test from wal-mart and it has enough reagent for a few CYA tests.