Plaster is like Sandpaper

[PoolDoc]

It almost seems as though I have both since I am able to scrape the grit off. Is that possible?

Unfortunately, yes. When you erode the surface of the plaster, what's left is much weaker and even friable.

The alk-step article explains what has ALREADY happened to your pool, in an extreme and uncontrolled degree. I was NOT telling you what you need to do!

I first ran into this problem, years ago on pools with UV ozonation and venturi injection of a little ozone and a lot of air. What happens is the aeration from the venturi strips all the carbonic acid (a component of carbonate alkalinity) and thus drives the pH up. If you neglect your pool, and allow the pH to remain high . . . there's no damage. But if you are conscientious, and adjust the pH, you consume remaining carbonate alkalinity by converting it to new carbonic acid. And then the process repeats.

I'm sure, with the popularity of infinity edges, waterfalls, and yes, bubblers . . . this is a very common problem. It's approaching 20 years since I first published an explanation of this. 10,000's of pool users have PROVED that I was correct, and Chem_Geek has published an extremely comprehensive spreadsheet that displays the whole cycle in excruciatingly comprehensive and detailed fashion. But because the pool industry as a whole has never been willing to acknowledge the fundamental errors in the way they've dealt with carbonate alkalinity, the problem continues, victimizing both pool owners and pool builders, who've been mis-instructed.

Unfortunately, the only fix for having REMOVED the top layer of your plaster is to replace it, with either a replaster job, or by refinishing with epoxy or a lesser pool paint.

I have vague recollections of having heard of people sanding pools -- it would be tedious, but if your remaining plaster is thick enough, it could probably be done using flexible diamond disks. I have had some diamond disks that would work, but those pads are no longer sold. I'm sure there's something out there, but I have no idea how much it would cost or how long it would take.

Sorry!

[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.