# Thread: Opening pool CYA 0 but adding CYA to 30, what level to shock

1. ## Opening pool CYA 0 but adding CYA to 30, what level to shock

I must have lost a lot of water over the winter because my CYA previously 40 is now showing as 0. So I know I need to increase that and have used the pool calculator to determine how much I need to add to get to CYA 30. I put solid CYA in a sock and have it dangling in front of the return water spout so it is being introduced to the pool over time. My questions is what level of FC should I maintain to shock the pool based on:

chlorine-cya-chart-t2346.html

At 0 CYA I should maintain .64 and at 30 CYA I should maintain 12.2 according to the chart.

Also a secondary question I live in Michigan and it's just starting to warm up so probably 2-3 weeks before I will want to swim anyway. Is there any reason not to just crank the FC up to like 25 just to kill all the algea knowing that I am not going to actually get into the pool for a couple weeks and that I will ensure the FC has dropped to a safe level before swimming?

2. ## Re: Opening pool CYA 0 but adding CYA to 30, what level to s

If you have no CYA and you have added enough to raise the CYA to 30, then go ahead and treat the pool as if the CYA is already 30 and shock the pool at 12 ppm FC.

3. ## Re: Opening pool CYA 0 but adding CYA to 30, what level to s

You don't want to raise it to 25 with no CYA in there - you risk bleaching the liner. Just follow the process for How to Shock your Pool in Pool School.

You will lose most of the FC on the first day anyway so picking a random number and throwing it in and leaving it for a few weeks doesn't really work...if that's what your asking?

4. ## Re: Opening pool CYA 0 but adding CYA to 30, what level to s

I wasn't planning on just getting to 25 and leaving it I was thinking I would maintain that. I guess mostly what I was wondering is when shocking say I do the 12ppm for CYA 30 is 12ppm the minimum and I can do anything over that as long as I don't let it dip below. Or do I need to stay pretty close to 12ppm. It sounds like I don't want to go way over or else I'll bleach the liner so I will try and stick as close to 12ppm as possible. Thank you both for the great info. I agree that most of the FC is going to be lost the first day so I need to check it pretty often. I was just hoping that if I put a lot in I wouldn't have to check it as often. Maybe once a day instead of 3 times a day.

5. ## Re: Opening pool CYA 0 but adding CYA to 30, what level to s

Or do I need to stay pretty close to 12ppm
Yeah, stay reasonably close to the 12 ppm. Depending on the condition of your pool water, you may lose a lot right away or it may be more slowly. I would check it at least twice daily during the shock process and bring it up to 12 ppm or so each time you test.

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