No Drain Acid Wash Questions

[xtexan86]

So I've read several previous articles about this topic on here and have had it done on my pool before, although the plaster layer that is on now is newer and different (Sider-Crete's roll on plaster). In applying the new plaster, there were areas I believe got "over-worked" in trying to get a smooth surface and have what I believe is just efflorescence that formed after the plaster cured. Additionally, an unfortunate rain shower also left water trails down the walls. The company suggests using Sure Klean 600 to remove this, but I would have to drain the pool - not a real issue as it's only 2000 gallons, but I'd prefer to avoid doing that. Another possibility I ran across was using Pool Stain Remover's $245 treatment, which can be done without draining. Judging from their before and after photos, it seems their product does a great job.

Currently, I am at about day 4 in this process. My water is cloudy so I can't really see the deeper part of the pool but it appears the water trails have been greatly diminished, however the areas in the "over-worked" areas don't show much difference at all. Since my Taylor test kit doesn't go below 7.0 pH I have no real idea how low the pH is. I have added roughly 3 gallons of MA, including another 1/2 gallon today. Two days ago my alkalinity was about 70 ppm but now when I do the test where you add the 2nd reactant, instead of turning green, the sample turns red so I have no idea what that means....that alkalinity is at 0? My calcium hardness has risen from about 280 and now sits at 400-440 ppm.

I'm not concerned about losing a bit of plaster doing this process. I am satisfied with the Sider Crete product but my attempt at trying to duplicate my original plaster color feel a little short, although the current color is nice, just a bit too turquoise for my tastes. I might attempt one more try at creating a better color but that's not the main issue. My question is how can I test for a really low pH? Take a sample to Leslies? Also, at what point should I try to address the cloudiness and how? Seems like draining some water is inevitable. Also, just how often are you supposed to brush the pool while doing a no-drain? Thanks!

 

[JoyfulNoise]

Your TA is zero and the pH is well below 4.5 (that's what it means when the TA indicator turns red right off the bat).

Is adding all this muriatic acid part of the stain removal process?? I really don't understand the process you are using. Do you have a technical bulletin or instructions??

You basically have an acid pool right now and, unless you intend for the plaster you applied to be completely etched off, I suggest you start adding baking soda to the water and brush until the TA test registers a reading. I would suggest adding 1 pound (or one box) of Arm and Hammer baking soda and then brush vigorously to disperse it all. Take a TA reading 30 minutes after adding the baking soda. 1 pound should raise the TA by 30 ...

 

[xtexan86]

Your TA is zero and the pH is well below 4.5 (that's what it means when the TA indicator turns red right off the bat).

Is adding all this muriatic acid part of the stain removal process?? I really don't understand the process you are using. Do you have a technical bulletin or instructions??

You basically have an acid pool right now and, unless you intend for the plaster you applied to be completely etched off, I suggest you start adding baking soda to the water and brush until the TA test registers a reading. I would suggest adding 1 pound (or one box) of Arm and Hammer baking soda and then brush vigorously to disperse it all. Take a TA reading 30 minutes after adding the baking soda. 1 pound should raise the TA by 30 ...

Thanks for the explanation. My understanding is for a no-drain acid wash to work, the pH needs to be very low along with no alkalinity. I'm attempting to just get as uniform of an appearance as possible by removing as much of the efflorescence as I can but I will strongly consider starting to reverse the process, but again, I'm not too worried about losing some plaster. Can you answer my other questions about what to do with the cloudiness and if replacing some of the water will be necessary?

 

[JoyfulNoise]

I understand how a no-drain acid wash works, but you talked about Pool Stain Remover or some other treatment so I was unsure of what you were doing.

The fact is, a No Drain acid wash should only be attempted for a few hours at most and not longer than 24 hours. If the stains and color variation don't change in the first hour or so, they never will. So now all you are doing is over etching the surface and making it more porous, rough and mushy. The acid component only affects calcium carbonate in the plaster, not calcium silicate. So what winds up happening is that the acid strips the carbonate out of the plaster surface but leaves behind the weaker silicate and any aggregate in the plaster such that the surface is much like sand. When you brush that, it will slough off as a cloudy, course debris. In effect, you've already over etched the surface and the cloudy water you are seeing is simply the result of suspended plaster solids in the water.

I suggest you terminate the acid wash immediately by adding either soda ash or baking soda, whichever you can get quickly. You are going to have to drain the pool and spray wash and brush the surface as it will be very mushy and weak. You will need to pump out all that wash water as well. Then you can refill the pool if the plaster is not too damaged. If the plaster is damaged, then you're going to have to start all over again with a new layer of Sider-Crete.