CYA Through the roof?

[Watermom]

Unfortunately, if your cya is well over 100 as it may be, it may take more than one partial drain/refill to get the cya down. If the cya really is 100, then draining half-way and refilling will take it down to 50. But, if your cya is really much higher than that, draining half and refilling will only reduce it by half. Even though it may still be higher than you really want it, one time draining half and refilling may at least get you down to a more manageable level. Go ahead and drain half, refill and then retest cya and let us know what it is and we'll advise you from there.

Your question -- how did the cya get so high? What have you been using to chlorinate with? You say "regular chlorine tabs and shock" which is most likely trichlor tabs and dichlor powder, both of which have cya in them. Actually, your scenario is a pretty typical problem that unsuspecting pool owners have. They use these products over a long period of time and don't realize that in addition to adding chlorine, they are also adding cya. Over time, the cya level builds up really high and as a result, the "normal" chlorine level that always worked before to keep their pool algae-free no longer will work. Higher cya levels require higher chlorine levels. And, that is the part that most pool owners don't know. I'm suspecting that is why you can't get your pool clear this spring even though you say you have shocked it to no avail.

I know it is a pain to do, but you really do need to drain half (maybe even two-thirds but no more than that at once) and then refilll and retest and we'll help you go from there. Also, look at the ingredients on the tabs and shock you have been using and let us know what they are. Like I said, probably trichlor and dichlor.

Let us know how it is going!