Hey TFP Forum, how many days can algae last if the FC is staying high and pool is being brushed?

Our IG pool was repaired last week after an entire summer down--a pipe on the pressure side had fractured under the concrete deck, so impossible to run filter. Water became green and opaque with frogs and mats of green-algae bio-slime on pool bottom. For the past week we've been following the method at the top of this section. Over the past three days or so the FC remains high without too much topping up, drops from 20 to about 12 over 12 hours. Sides have been brushed and the bottom scooped almost daily (missed two nonconsecutive days). CYA was very low at the beginning. We added about 5 lb. CYA over the first few days using a sock in the skimmer...CYA level results are still kind of murky, so to speak, but clearly higher than when we started.

The question is, the water turned grayish green, or green with a little gray, but isn't clearing at all. It's still opaque. And the filter pressure hasn't changed or gone up the whole week, which confuses and concerns me.

Is this amount of time without clearing or pressure rise to be expected, and all it needs is to maintain FC and add more P.O.P.P.? Thank you for reading and thanks for your input!

22K IG Gunite pool
Upright Anthony VA-52 DE filter, pressure 20 lb
Pentair Whisperflo pump
Taylor test kit

Today's numbers:
Water 67°F
FC 20 ppm
TC hard to tell at this concentration, but > 20 ppm
pH 7.2
CYA ~35 ppm - best guess with cloudy water.
Total alkalinity 80
Calcium hardness 40 ppm

As long as you are losing FC, you are killing algae. Continue the process until your FC holds to within 1 ppm or less of loss overnight, you CC is < 0.5, and you pool water has cleared.

OK thanks, reassurance much appreciated!
Steve C.

No problem!

A DE filter should be giving you fits. I'd expect you'd be needing to backwash it every couple of hours at best. Chemically it sounds like you are on the right track, but it doesn't sound like your filter is working to me.

@John T

That's a good question. The filter screens have a few small tears, and you can see some DE blow in through the jets when added to the skimmer. But there doesn't seem to be much DE settling on the steps and the pressure has been about 20 lb since right after startup. Normal startup pressure is 10 lb with clean screens and a fresh DE charge.

Without intact screens, your filtration will be subpar and you will have trouble getting to where you want to be.

You should clean your filter when the psi increases about 6 above clean start-up psi as suggested in Pool School: pool-school/cleaning%20pool%20filters

Also verify that your gauge is working properly.