High CYA, high TA, and low PH

SCRealtor

Member
May 16, 2019
15
Orange County, CA
I've moved to a house with a pool that wasn't well maintained. The owner used chlorine tabs for years without ever draining the pool, so the CYA is through the roof. My testing kit only goes to 100 so I'm guessing it's at least 150, if not higher. Additionally, the PH is typically low (7.0 to 7.2) and the alkalinity is high (180 to 200--the fill water tests at 210). The high CYA or combination of other factors appears to have created a chlorine lock. I can put chlorine in the pool one day with a reading of approximately 5 ppm and within a day or two it's below 1 ppm.

I know the best thing to do would be to drain a good portion of the pool to lower CYA, but I live in Southern California and, as usual, we are in a drought year. I'm planning on doing that next year when I have the pool replastered and retiled. Without many options available, I opted to try the Bio-Active CYA Reducer. I've heard mixed results, but didn't feel I had many options.

I tried to get my chemistry within their prescribed ranges, but my alkalinity remains very high, despite adding multiple drops of muriatic acid. I've used Borax to help keep up PH. It had been up to 7.6, but is down to 7.2 after an acid drop today. I've tried aeration in the past, but I didn't see much success.

Any suggestions?
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,637
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
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Chlorine
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SWG Type
CircuPool RJ-45 Plus
I wouldn't use borax as it also raises the TA as well. Not as much as soda ash, but you don't need the TA any higher. What you need to do is aerate the water like crazy. That will increase the pH to 8.0 naturally so you can hit it with acid again to lower the TA, then repeat.

Now I will say all of this means nothing if you don't get that CYA down. You really need the CYA at least below 80, ideally more around 60 or so if that is a non-salt pool.

Lastly, how are you testing? Accurate testing with a TF-100 or Taylor K-2006C kit is all that matters. If you don't have one of those, everything could be guesswork so be careful. Don't forget to update your signature. :)
 

Oly

Gold Supporter
Jun 28, 2017
2,340
Fresno, CA
Pool Size
27000
Dilute your pool test water 50/50 with tap water and double the results for your actual CYA ppm assuming you have a solid test kit.
As for your options, find a business that will filter your water using a reverse osmosis R/O system and get a quote.
You will still lose some water but it may be allowed in your county.
 

SCRealtor

Member
May 16, 2019
15
Orange County, CA
I wouldn't use borax as it also raises the TA as well. Not as much as soda ash, but you don't need the TA any higher. What you need to do is aerate the water like crazy. That will increase the pH to 8.0 naturally so you can hit it with acid again to lower the TA, then repeat.

Now I will say all of this means nothing if you don't get that CYA down. You really need the CYA at least below 80, ideally more around 60 or so if that is a non-salt pool.

Lastly, how are you testing? Accurate testing with a TF-100 or Taylor K-2006C kit is all that matters. If you don't have one of those, everything could be guesswork so be careful. Don't forget to update your signature. :)
Taylor kit
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,420
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
My testing kit only goes to 100 so I'm guessing it's at least 150, if not higher.
With a Taylor K2006C, to test CYA above 100, dilute the pool water 1:1 with tap water. Use that mixture to do the test. Then double the result.
 

SCRealtor

Member
May 16, 2019
15
Orange County, CA
I wouldn't use borax as it also raises the TA as well. Not as much as soda ash, but you don't need the TA any higher. What you need to do is aerate the water like crazy. That will increase the pH to 8.0 naturally so you can hit it with acid again to lower the TA, then repeat.

Now I will say all of this means nothing if you don't get that CYA down. You really need the CYA at least below 80, ideally more around 60 or so if that is a non-salt pool.

Lastly, how are you testing? Accurate testing with a TF-100 or Taylor K-2006C kit is all that matters. If you don't have one of those, everything could be guesswork so be careful. Don't forget to update your signature. :)
I had read that Borax didn't tend to increase TA along with PH, but I'll hold off on using it for now. As for aeration, several months ago I tried to aerate the pool. I got a high powered shop vac turned onto blower, submerged the end of the hose, and let it run for hours multiple days in a row. I also turned on my jacuzzi and blasted the pool surface with my high powered leaf blower. I didn't see any change in PH. But, I'll give it all another shot.
 

SCRealtor

Member
May 16, 2019
15
Orange County, CA
I finally decided to have a company do the reverse osmosis water filtration on the pool since everything was so out of whack and I'm in a drought state so I didn't want to drain and refill. My TA dropped from 120 to 60, so he actually added some bicarb afterward. Similarly, CA dropped from 500 to 120 so he added some calcium. My arch enemy, CYA, dropped from 150 to 20. YES!!!! My TDS dropped from 3640 to 690 and my salinity from 2479 to 479. I'm looking forward to an algae free pool and not having to buy gallon after gallon of chlorine.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,637
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
Good to hear your CYA, while low now, is at least something more manageable. When you get a chance, be sure to update your signature with all of your pool and equipment info to include which test kit you have. Post a full set of water test results at any point forwards and we'll be happy to help if you need it.
 
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