I didn't check the pool chart before I responded to your last post. Sorry 'bout that! Regarding opening --- we see many pools where the CYA biodegrades over the winter and leaves you with a pool full of ammonia as a result. This can cause a HUGE chlorine demand where it takes tons of bleach before you can hold any chlorine in the pool. This can happen in any pool but especially when your CYA is as high as you report yours to be, if it does happen, it is especially a problem to clear up. Who knows how far over 100 your CYA actually is? By the way, how did it get so high?