Trouble balancing water

benz55

Member
Jun 16, 2020
9
Bay area , CA
Hello,

I have a 17k gallon pool plaster cartridge filters and this year I seem to be having alot of issues with balancing the water:
My current test results are :
FC: 2.47
TC: 2.8
Ph:7.9
Alk: 77
CYA: 119
Calcium: 202
Iron/Copper : .01
Phosphates: 1691
Pool water is crystal clear with occasional yellow algae spots that brush off easily
I have switched to liquid chlorine also due to the CYA issue.

What I have done:

I recently had very high CYA values so I drained 2 times to bring it down from 200 to 120.
Added Muriatic acid to bring down PH but it continues to hover around 8. recently added 2 quarts and it made only a small change over several days (.01)
I Added 1.5L of Phos free ( Clean filters before and after a 48 hr run) It only brought my Phospahtes from 2000 to 1691.,
I tested all using a taylor kit. The only item that differs is the Alk. I measure 110 where the pool store measures 77 but it indicates this is due to the CYA level and it made an adjustment to the calculation.

So the recommendation I have now is to increase ALk first , but I dont believe this is right because its a calculated adjustment because of CYA. Another pool store said Alkalinity should be left alone and I should add muriatic acid and phos again.

So my question is what should I be chasing first. So far I have been given bad advice from the pool store and the chemicals I have been adding have little effect. I believe I am following proper directions for adding everything and measuring carefully.

Thanks!
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Here's what I would suggest:
- Without a doubt #1 ... use a TF-100 or Taylor K-2006C to test your water. Anything else is questionable.
- Stay out of the pool store unless you need a brush or pool toy. Advice is generally wrong (like above) and the products costly
- Phos-Free will do nothing for you; the CYA and TA are not related
- Update your signature with all of your pool and equipment info. It matters with each reply. Include your test kit.
- Your CYA is obviously high. Getting that down to around 50-60 (non-salt pool) or 70-80 (salt pool) is step #1.
- Then you'll need to follow the SLAM Process because you have algae. Chlorine in the proper amount (with proper testing) is the cure.

But in all cases, you must have one of those proper test kits. See Test Kits Compared for more. I recommend the TF-100. Read our ABCs of Pool Water Chemistry and the Vital Links below in my signature. Those will help you.
 

BR1

Member
Jun 20, 2020
9
NY
as above, the TF-100 kit is super user friendly. there is zero need to use a pool store. oddly enough....don't they all push the chlorine tablets?
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,930
San Dimas, CA (LA County)
I wouldn't add anything right now. You'll just be pouring money down the drain. If the CYA is 120, it's too high to SLAM, and since you're finding algae spots, the SLAM Process is in your immediate future.

If for whatever reason you can't replace any more water, you need to adjust pH. Ignore your TA -- whether its 77 or 110 is immaterial--you only need it to calculate the acid dose and in that case you use the unadjusted value in poolmath. Then you need to raise FC UP. Way up. Just maintenance, not necessarily getting ahead of the algae, means you should target 15 FC every day and not let it get below 9. And be aware that at that FC level, pH readings can get a little sketchy and often read falsely high. Pool maintenance is a lot easier at lower CYA levels.
 

benz55

Member
Jun 16, 2020
9
Bay area , CA
Here's what I would suggest:
- Without a doubt #1 ... use a TF-100 or Taylor K-2006C to test your water. Anything else is questionable.
- Stay out of the pool store unless you need a brush or pool toy. Advice is generally wrong (like above) and the products costly
- Phos-Free will do nothing for you; the CYA and TA are not related
- Update your signature with all of your pool and equipment info. It matters with each reply. Include your test kit.
- Your CYA is obviously high. Getting that down to around 50-60 (non-salt pool) or 70-80 (salt pool) is step #1.
- Then you'll need to follow the SLAM Process because you have algae. Chlorine in the proper amount (with proper testing) is the cure.

But in all cases, you must have one of those proper test kits. See Test Kits Compared for more. I recommend the TF-100. Read our ABCs of Pool Water Chemistry and the Vital Links below in my signature. Those will help you.
Thanks for the detail. I have been able to keep the chlorine level at normal ranges even though the CYA is high. I was expecting as I add water over the summer months it would decrease the cya eventually. I was believing my algae issues it related to the phosphates being so high. Do you believe phosphates at the level of 1700 is not an issue?
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
The phosphates is not your problem. Only in some rare situations do we worry about a phosphate number. One of your biggest problems is that you have algae with a high CYA. CYA primarily goes down with a water exchange. A small amount of CYA gets used-up each month, but only about 3-5 ppm. A high CYA requires a very high FC SLAM level to kill the algae - see FC/CYA Chart. You can see that once the CYA is over 100, the FC must be quite high, and maintained that high until you pass all 3 SLAM criteria. Also remember that when your FC is over 10, which yours almost always needs to be right now, it makes the pH test high as well.
 

Dtkokay

Well-known member
Dec 31, 2019
313
Houston, Texas
Thanks for the detail. I have been able to keep the chlorine level at normal ranges even though the CYA is high. I was expecting as I add water over the summer months it would decrease the cya eventually. I was believing my algae issues it related to the phosphates being so high. Do you believe phosphates at the level of 1700 is not an issue?
Your chlorine is NOT in the normal range. FC needs to increase as your CYA increases. With a CYA over 100, your FC of 2.5 is way below where it needs to be and is basically doing nothing. You practically have no chlorine, with that level of CYA.
 

Maureen03

Gold Supporter
Jun 25, 2020
16
New Smyrna Beach, FL
Just remembering (pre TFP) when I was adding stabilizer with no results showing on my little test strips. And kept adding it. I have since purchased a Taylor 2006 kit and learned a lot from pool school. Naturally, there really was LOTS of stabilizer present. I have read and learned (just like they said). It’s really starting to come together.
 
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