Best way to add Cya
I see a lot of posts where people have difficulty opening a pool. I see posts about adding way too many chemicals, chasing test results.
Open pool, get filter up running first. Check for air leaks, etc. if alkalinity isn’t below 50 don’t worry, ph hopefully is low or in range. Brush, brush, brush. Add salt. Filter runs non stop. Then slam (10 to 15 ppm) it at night. The first slam will usually make the water go cloudy and overwhelm your filter. Expect the big cloud. FC will prolly be at 0 next morning. Don’t sweat it, vaccum and let filter run, it will prolly start looking better throughout the day as the filter does its job. Repeate the process at night. Prolly will need a backwash after 24 hours. The second slam usually does the trick.
Nothing else. Chlorine and your clean filter.
I did post this just to show the sock method for adding cya. 1 sock by the return key and 1 in the skimmer. 2lbs each sock. Cya takes forever to dissolve. Let a week go by for testing so you don’t over shoot your target. Also error on the side of not enough. Math wanted 5 pounds to get to 40 … so I did 4 lbs.