Having to SLAM but not really sure why...third time now

Alright now I get it. Thanks again.

FWIW, my pool is no longer depositing the strips of green (or glob of white) as seen in the pics above. Have been checking about every 2-3 hours and basically having to add a half gallon each time to boost the FC back up from 24-25 to 28. Of course, the day I'm doing this is the first absolutely sunniest of sunny days we have had in weeks.

Interesting (or not) factoid: my filter pressure has gone down since starting this, not up. Running the pump non stop at a fixed 2400 RPM, did a backwash before starting slam and pressure was 9.5. Now just over 24 hours later while the pool is looking better and I’m presumably filtering things (normal day to day stuff and hopefully dead algae), pressure is 8.5. Seems backwards.

Meant to bump this thread last week but never got around to it. Things are all good in my hood again but I'll be Darn if I didn't get another algae bloom and had to SLAM my pool again. As before, I'll give a breakdown of test results and the ensuing pattern:


We were noticing the same green spots collecting in the same areas as before (photos on page 2) around the first of May, along with the puffing while brushing. Have never seen it it on the walls at all, just the floor/shelf/stairs. I really had myself convinced it was pollen until it failed the OCLT.

So on May 4 I dropped the pH to 7.2 and added chlorine to get it to 20, kept up with it rigorously for a couple of days and considered myself to have completed the SLAM after a successful OCLT from May 6-7th. Been letting the FC drop gradually since then and the water remains clear with no further algae appearing in the typical areas.

All in all really not too painful, just annoying and frustrating. There is essentially nowhere for algae to be hiding and I'm clearly well within, in fact more so at the upper end of the recommended range of free chlorine. I may try and remove the weir door to more closely inspect and thoroughly scrub it. Dead spots in the pool perhaps? I could redirect the returns and/or adjust the suction valve to draw more from the main drain (probably 80% skimmer currently), but that would all just be a guessing game I suspect. I also run the pump at a very low speed most of the day, I could bump that up (along with my power bill) if the thought is that more circulation could help.

I also just after this SLAM added boric acid to get my borates to around 35 or so and will likely use some borax to go a little higher. I don't expect that alone to solve the problem, but understand it might help prohibit algae growth.

A fair question, I never watch it through its full paces but have often wondered how good it could possibly do in the corners where the walls meet the floor. It's the only thing I'd prefer about a pressure Polaris, that swoopy brushy tail!

I feel we make a pretty good effort to brush but maybe not that often enough. We'll get a more regular regimen going with that, paying special attention to the spots in question.