Plaster is like Sandpaper

[PoolDoc]

Someone else was asking about sanding a pool, and I had better results when I searched for his info:

I doubt standard sand paper is what is used.

A grinder like this: Bosch 1994-6 9-Inch Large Angle Grinder

with pads like these:
http://www.tedpella.com/Material-Sci...ms.htm#_814_10
http://www.rockstardiamond.com/polis...FRJk7Aod-gcAcQ

You'll need to see what's required to attach those pads to that grinder. Be aware that sanding an entire pool, even with a 9" grinder and diamond disks, is a slow process.

[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.