Pool chemistry out of wack

[H-12 1/2 Mike]

Just finished my weekly test with the following results:
Cl = 3.5/3.5
Ph = 7.5
TA = 190
CH = 110
CYA = 100
TEMP = 51
My question is: Which do I adjust first? I just added the gal of bleach to bring the chlorine back to 8ppm. The cyanuric acid is a result of a 4 lb addition made on Thursday to bring it up from 20ppm.
The pool is gunite @16,400 gals. I believe the CSI = -.37.

 

[JasonLion]

What test kit/device are you using to test the water?

4 lbs of stabilizer/cyanuric acid would raise the CYA level from 20 to 50, so either the level was much higher than 20 before, or is much lower than 100 now, or either your pool size or the amount of CYA you added was way off. My inclination is to suspect the testing, either before or after or both.

Without reliable test results you are just taking wild guesses about what to do, so it is well worth figuring out the testing question before doing anything else.

 

[zethacat]

100 is too high for CYA. If those test results are correct then the first thing you need to do is drain and refill half the pool.

 

[H-12 1/2 Mike]

The test kit is a Taylor K2006. I made the CYA adjustment after 6 consecutive tests (Weeks) of 20 as a result. This is the first test after the addition of the CYA.

 

[pwrstrk]

I'm hoping this is testing error because if it isn't you going to have to lower that level by replacing some water.
Let your water sample come to room temp for the CYA test.
I get the same results as Jason for adding 4lbs of CYA. Using pool math that would raise your CYA level by 30 if your pool volume is correct.

 

[H-12 1/2 Mike]

Had the pool for 20 years so I am pretty confident of the volume. I don't plan on doing any adjustments to the CYA but will let the topping off of the water take care of that. The only chemicals that I adjust daily are the CL and acid if needed. As you can see that it took 6 readings before I made a correction to the CYA. I guess my concerns are more of the CH and the TA.

 

[JasonLion]

What were CH and TA previously?

Assuming your test results are correct, CH should be raised, and TA should be lowered. But something else is going on here and it seems more important to figure out what first.

 

[H-12 1/2 Mike]

Jason, my fill water has a TA of 190. When I cleaned the filters on Wednesday I noticed the water was very murky in the filter housing. In 20 years of cleaning these units I had never seen this before. When I cleaned the cartridges I noticed a gray residue was left on the driveway. Never seen this either. Recently they have started major construction on I-35 about 2 miles from the house. With the higher than normal winds, could this be a factor?

 

[JasonLion]

Yes, it is quite possible for wind to be blowing in dust from the construction site.

 

[H-12 1/2 Mike]

Update: the cya is now down to 60 and the CH has been adjusted to 290. The problem now is still the TA at 190. How fast should I make the TA adjustment to 90 ppm?

 

[JasonLion]

With high TA fill water, it may or may not be practical to keep TA as low as 90.

The main issues driving how quickly you want to lower TA are the speed at which PH goes up, and problems with high CH levels. High CH doesn't seem to be an issue for you, so it comes down to PH drift. If PH is going up annoyingly quickly, it is worth lowering TA quickly. If your TA is relatively stable, then just lower the PH to 7.2 any time it gets to 7.8 and the TA will come down eventually.

 

[H-12 1/2 Mike]

Perfect. Thank you!

 

[H-12 1/2 Mike]

All of my problems with high ph was caused by continuously adding water (2.25" per day) because of a pool leak. The leak has now been repaired and all of my chemistry has now stabilized and now I am in control.

 

[jcowart]

Yea, don't get hung up on a TA number. If your pH drift is not too bad then as Jason said just manage your pH. Your TA will then find it's happy home. Every pool has its own personality.

 

[Divin Dave]