Remaining Stains or Algae?

I would appreciate advice regarding remaining stains.

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This is my friends 22000 gal pool. She bought the house last summer her CYA was over 300. She partially drained and refilled and tried to maintain a high level of chlorine but really it was impossible. Over the winter with refilling and an occasional backwash her CYA came down to around 50 but she had a nasty case of algae. We decided last week was the week to dig in and clean up.

Adjusted the alk to 120
raised the ph to 7.2-7.4 (aerated to get it here after alk adjust)
shocked the heck out of it to get the chlorine level to about 40ppm. Brushed brushed and brushed. T
he Chlorine level would drop to 16 and we would crank it back up with 10% liquid chlorine. It was using chlorine so fast we could barely keep up. I'll have her count the gallons and then I'll post.

5 days and it looks so good! This forum is the best thing since ..well I don't know what!

My question is..those stains that are still there..algae? I've tested and we don't have any combined chlorine. Although we're having to use 8 parts distilled water to 1 part pool water because the levels are so high.

It's hard to get the brush around those tricky areas. We're using an algae brush when we can and then the toilet brush attachment where it's tight.

The chlorine isn't disappearing nearly as fast. OH, we also cleaned that filter and put new DE in..and plan on doing it again this weekend.

What do you all suggest?

and ..any idea on replacing those pop up heads? Prices are 50-75 EACH...just general searching around on the internet..

Thanks a bunch!