Algae and High CYA?


Apr 28, 2021
South Austin, Texas
I am in the middle of a SLAM and losing faith. I started a SLAM on Friday because a series of bad decisions led to a cloudy bloom, but due to my high CYA levels (CA:80) it took a ton of chlorine to get to the initial SLAM levels. Of course, it also rained 2.5" this weekend; I have stayed on top of the testing and chlorine levels, but I am really not seeing any progress in my SLAM. This is my first time and I am more than a little concerned...Can anyone tell me that I am doing it right and it is okay?

FC: 1.5
CC: 0.5
pH: 7.3
TA: 80
CH: 250
CYA: 80
Temp: 78

Current SLAM:
FC: 29.5
CC: 0.5
CYA: 80

With my CYA levels as high as they are, should I consider draining down and replacing water to lower the CYA or should I continue the SLAM? I have a relatively small pool (6700-gal), but vinyl and above ground and I have read it isn't the best idea to drain these below the skimmer. As an aside, how far below the skimmer can I lower the water level without damaging the pool/liner? I have a submersible pump.

Added pressure: The wife has family coming over for Mother's Day. Should I go ahead and temper expectations?
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Silver Supporter
In The Industry
Aug 15, 2017
Spring Valley, NY
Well my take is, you have a tablet chlorinator and that will give you the high CYA. You can probably drain half the pool and fill back pretty fast as the pool volume isn't who knows what. Refill and do a slam at say 40 CYA which is easily achieved. Start using liquid chlorine so the CYA doesn't get that high again. You probably got into the problem as the chlorine management at that level isn't as beneficial as with lower CYA.
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Well-known member
Jun 19, 2020
You can safely drain down to within about 1-2 feet from the bottom.

Brush the walls and floor and then drain half. That will get rid of half your CYA, and also get rid of half your algae. Refill and your SLAM will go much quicker. Keep your filter running 24/7, backwashing whenever pressure rises 25% over clean pressure.


Gold Supporter
Bronze Supporter
TFP Guide
Jun 29, 2016
Tampa, FL
Pool Size
Salt Water Generator
SWG Type
Intex Krystal Clear
While I would definitely drain water to get your CYA down, I would also say that two days isn’t enough time to clear a green cloudy pool. Patience, frequent testing and dosing, and brushing regularly, along with a healthy chunk of patience, will get you to the finish line.
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