Any way to reduce CYA without draining?


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
CYA of 100 is not that bad, especially if your pool is clear and there's no SLAM in you immediate future.
It may seem "not that bad" but you are asking for trouble. Any pool that has CYA in excess of 80 ppm is outside suggested TFP ranges and I believe it will eventually bite you.

Some may get away with it, even for years, but the FC you save is simply not ever worth the punishment you will get if you have an algae bloom and a CYA of 100+
Jun 17, 2019
Barrington IL
Welcome to the forum!
The only way to substantially reduce your CYA level in your pool water is to remove some of that pool water and replace with fresh.
How did you test the 100 ppm CYA? That is the limit of most test devices, especially at pool stores.
Can you fill out your signature so we know what pool type, volume, equipment, etc you have?

I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.
Hi Marty,
I've read about your water exchange method, and I want to try it. My water supply can provide 10 gpm, and I have a pump that can match it. You recommended draining 75% of the water, which will take about 16.3 hours at my flow rate. Is it feasible to use your exchange method for that much water (about 9,800 gallons)? My supply is well water, which is much colder than my pool--about 48 degrees or so vs. 76.
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Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Absolutely the process will work. With those water temperature differences, it will be well segregated.

Put you pump on the top step and your hose in the deep end.
Jun 17, 2019
Barrington IL
You DO have algae problems. "My pool has just a little green tinge on the walls, very slight, but the water looks nice and clear. " Will it still be nice and clear after you brush the walls?

Your pool guy may have been dumping algaecides in the pool. Maybe even using the "blue" trichlor pucks with copper added. There's no denying copper is a great algaecide; it just doesn't kill bacteria and viruses fast enough and tends to build up and stain the walls and turn blonde hair green.
I would personally drain at least 75% of your water and replace with fresh. But, as others have said, you can manage high CYA if you want. Testing your pH is the issue. Getting an accurate pH test with FC above 10 ppm is problematic.

Your 'pool guy' doesn't swim in the brew that others have. Once you have true TFP water, you will never go back to the chemical brew of trichlor, 'shock', and algaecides ---
Hi Marty,
I am about 80% done with the water exchange, but now my water is brownish (I have well water). I presume it's iron. Can you recommend how to get rid of it? I've seen reference to the polyfill in the skimmer trick, but is there anything else I can do to help the situation?



Well-known member
Aug 14, 2018
Scottsdale, AZ
Sometimes, we get lucky and stumbled across something that worked for us for the few months we've had the pool, find this page, and find out we've pretty much been doing this without even realizing it. :)
Just letting you know I'm also currently doing a water exchange to get my CYA down. My fill water is about the same temp as my pool so I have the pump in the deep end and fill water at a bucket on the first step.
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