Plaster is like Sandpaper

[Mikes Pool]

Well Doc, it is what it is. I don't think I want to sand it. We will just have to plan on having it re-plastered. In the meantime I just want to keep the water balanced. We were out of town for the weekend so I checked the water chemistry before we left on Friday. Everything was good except pH. I added 2 pints of acid to bring it down to 7.4. I checked it today (Sunday) and it was back up to 8.0 so I put 3 more pints in it today.

My K-2006 arrived on Saturday so I used that today. Here are my numbers:

Chlorine - 1.0 ppm, combined - 0.0
pH - 8.0
TA - 110
CH - 320
CYA - 90

The Saturation Index was +0.5 and after adding the acid it should have dropped to -0.05. As you can see I am still chasing the pH. Will I have to keep adding acid several time per week? I can't help but feel that something is causing the high ph but as you can see my numbers all are within acceptable limits. Any ideas?
Thanks.

[PoolDoc]

As you can see I am still chasing the pH. Will I have to keep adding acid several time per week? I can't help but feel that something is causing the high ph but as you can see my numbers all are within acceptable limits. Any ideas?

Have you turned off the bubblers?

You really cannot run them continuously. If you want to do so, you MUST readjust your chemistry to allow for a terminal pH of 8.0 - 8.2.

[Mikes Pool]

Have you turned off the bubblers?

You really cannot run them continuously. If you want to do so, you MUST readjust your chemistry to allow for a terminal pH of 8.0 - 8.2.

Yes, I forgot to mention that the bubblers are turned off. That is the first thing I did.
Do you agree that my chemistry looks ok?

[PoolDoc]

You need to maintain a chlorine level around 10% of your CYA (9 ppm), so your chlorine is way too low. You'll grow algae at your current level. But use bleach, not your SWCG to shock. Trying to 'boost' or 'shock' using an SWCG leads to greatly reduced cell life.

Your pH is too high; you need to keep it lower. But you may be dissolving pool plaster that's ALREADY softened and weakened. So, I wouldn't go too low. Maybe, 7.6 - 7.8.

BUT . . . you need to inspect your SWCG cell; the plates may need to be cleaned, given all the movement in pH, calcium and TA levels.

[Mikes Pool]

You need to maintain a chlorine level around 10% of your CYA (9 ppm), so your chlorine is way too low. You'll grow algae at your current level. But use bleach, not your SWCG to shock. Trying to 'boost' or 'shock' using an SWCG leads to greatly reduced cell life.

I've never used bleach, is there a formula for how much to use?

Your pH is too high; you need to keep it lower. But you may be dissolving pool plaster that's ALREADY softened and weakened. So, I wouldn't go too low. Maybe, 7.6 - 7.8.

Today, my pH is 7.4 after adding acid last night. My alkalinity went from 110 last night to 70 this morning. Is that because I turned the bubblers off? Am I at the point now where I can control my pH by bringing up the alkalinity?

BUT . . . you need to inspect your SWCG cell; the plates may need to be cleaned, given all the movement in pH, calcium and TA levels.

I will inspect the SWCG tomorrow.

[PoolDoc]

Your PF is 4.8. Walmart 8% bleach, per gallon, is equivalent to 0.7 lbs of chlorine gas. So 1 gallon will add 4.8 x 0.7 ppm chlorine to your pool, or 3.4 ppm.

Likewise, if you use dichlor (61% available chlorine in some forms), 1 pound would add 4.8 x 0.61 = 2.9 ppm.

I'm not sure why your pH is moving; there are multiple possibilities. Focus on managing your chlorine, keeping your pH between 7.0 and 7.8, cleaning your SWCG. Run things for a week or two so you establish 'normal' patterns.

[Mikes Pool]

I am posting my pool readings for the last 11 days. As you can see pH is all over the place. I pulled the SWG and it was pretty clean but I followed the mfg. instructions and acid cleaned it anyway.The water is very clear and I don't see any dust when I brush. Come to think of it, last year when I brushed I would always see dust. That must have been when my plaster was being attacked! Also, last year is when my original Jandy SWG needed replacing. During that time my pool chemistry got out of whack as the SWG quit right before our vacation and I neglected the pool for about a week. It's all starting to make sense now. I feel like I have things under control now but it is driving me nuts chasing the pH like that. Any suggestions on the pH? Am I resigned just adding acid every other day?

As for the chlorine, I read elsewhere on your site that 4.5% of CYA is good for a SWCG pool and you are saying 10%. Why the difference?

One more thing Doc. What are your thoughts on a "No drain acid wash"? My plaster is blotchy now and I was wondering if that would help with the blotchiness and maybe smooth the plaster at the same time.

Here are my pool readings:


Date FC/ CC/ pH/ TA/ CH/ CYA

7/13 1.0./ 0.0/ 7.8/ 110/ 320/ 90/ Added 3 pts. MA

7/14 2.5/ 0.0/ 7.4/ 70/ 300/ 80/

7/15 2.5/ 0.0/ 7.6/ 100/ 300/ 80/ Added 1 pt. MA

7/16 3.5/ 0.0/ 7.8/ 100/ 300/ 80/ Added 1 pt. MA

7/17 4.6/ 0.0/ 7.8/ 80/ 300/ 75/ Rain, no acid

7/18 5.4/ 0.0/ 8.0/ 100/ 300/ -- Added 1 pt. MA

7/19 5.0/ 0.0/ 8.0/ 75/ 300/ -- Added 2 pts.MA

7/20 6.8/ 0.0/ 7.6/ 75/ 300/ --

7/22 6.5/ 0.0/ 8.0/ 100/ 275/ 80/ Added 1 pt. MA

7/23 5.8/ 0.0/ 7.8/ 75/ 275/ --

7/24 6.4/ 0.2/ 7.8/ 75/ 275/ -- Added 1 pt. MA