I suspect that maybe you didn't kill all the algae. With a cya of 60-70, the chlorine level you need to regularly maintain is 5-10. You said that you raised your chlorine level up to 7 to try and kill the algae. That isn't high enough for your pool. Shock level for a pool with that much cya is about 20ppm. Take a look at the chart at the following link. I have a feeling that may be the problem - that you really didn't eradicate the organic stuff in your water. Like Dave said, you will probably find that you have a CC reading. My advice is to shock the pool for a few days. Try and maintain the high level without letting it yo-yo up and down. To do this, you'll need to test at least a couple of times a day (3x a day is even better) and each time add enough bleach to take it back up to shock level. BTW - uncover your pool while your chlorine level is high so you won't damage your cover.
http://www.poolforum.com/pf2/showthread.php?t=365
Bookmarks