Is Dry Acid bad for the plaster?

Jump to latest Follow Reply
T

three4rd

0
Jul 20, 2014
206
Berks County, PA
Hi,

An interesting post was added to my thread on lowering pH and TA, having to do with the addition of sulfates in the water as being harmful to plaster and grout as opposed to using MA. I have never run across this before, and have been using sodium bisulphate for 25 years (and still had the original plaster until I recently renovated). So many companies and pool professionals seem to recommend the use of dry acid over MA, which is probably how I got started with it. Is this something to be really concerned about? I certainly have been using alot of acid since the renovation (about 25 pounds of Lo N Slo so far). Hopefully once the plaster cures I won't be needing to make excessive pH adjustments.

Thanks for any thoughts.
 
Most people never use enough to get the sulfate levels into a range where there could possibly be an issue. But if you are using a lot, the odds of eventually getting a high sulfate level go up, and the fact that it costs quite a few times more than muriatic acid start to be significant.
 
Hi Chem Geek,

Thanks for those links. The article by the Pool Water Treatment Advisory Group says to avoid sulfate concentrations in excess of 300 mg / L. Out of curiosity I wanted to figure out how many pounds of sodium bisulphate I would need to add that would be equivalent to a 300 mg / L concentration.

I calculated that my pool holds 45,425 liters (12,000 gallons). 1 pound is equal to 453.5 mg. My calculations indicate that the level beyond which damage could occur is 13,627,500 mg. or 30,049 pounds of dry acid, unless of course a 'pound' of Lo N Slo is an inaccurate measurement in the equations that I used in my calculations. I suspect this unlikely, and so if my math is correct then the point is that one would have to add aLOT of dry acid before any harm would be done, as JasonLion suggested. When he mentioned about it being unlikely that one would reach an unsafe level, that's what got me thinking about trying to find out how much exactly would need to be used that would even come close to the 300 mg / L referred to in the article.

All that being said, I'm sure that MA is probably better to use, but I feel much more comfortable with the Lo N Slo. It'd be interesting to know what percentage of pool owners use dry vs. MA.
 
Wrong. 1 pound is not 453.6 GRAMS, but is 453,592 milligrams. You are off by a factor of 1000. (45,425 liters) * (300 mg/L) = 13,627,500 milligrams which is 30 pounds of dry acid. 1 pound of dry acid in 13,000 gallons only lowers the pH from 7.8 to 7.5 in a 12,000 gallon pool so it is conceivable to be doing this every week if the pH is rising a lot so one could get to 30 pounds over a season or two.
 
Hi chem geek,

My mistake - I see where I went off with the conversion. While my amount (30,000 lbs) sounds too high, 30 pounds sounds like too low an amount. I'm already at over 24 lbs in a week since the new plaster went in. For someone with new plaster that keeps generating higher pH levels, the amount I've been adding doesn't seem like an extraordinary amount.

- - - Updated - - -

JasonLion said:
Most people never use enough to get the sulfate levels into a range where there could possibly be an issue. But if you are using a lot, the odds of eventually getting a high sulfate level go up, and the fact that it costs quite a few times more than muriatic acid start to be significant.
Click to expand...

JasonLion,

Given the reply I just got from chem geek, would 30 lbs. of dry acid be enough to begin causing problems? I'm wondering what the 'range' is that you are referring to?
 
Certainly nothing is wrong with using MA....just that I never used it before and everything I've read and heard indicates that dry is much safer to use and easier to handle. That's reason enough for me. I simply cannot believe that everyone out there using dry acid over the years is doing bad things to their plaster, but if such is the case, all the better for those in the business of doing renovations and replastering. I will certainly consider switching though. I have no doubt that MA is much cheaper, but I'm really not concerned about that. One does not build an inground pool or take up any hobby or interest that involves a substantial investment in order to save money, imho :) I suppose I could go to walmart or someplace and get el cheapo brand chemicals, but I'd rather go with a more well-known brand. Maybe I've been brain-washed by my pool store over the years too....could easily be. I'd just rather not deal with having to worry about using that strong acid.
 
We're just providing you with information including links that refer to problems with concrete (plaster) when sulfates get high. With the amounts you are adding, you are certainly getting them high. We simply don't have enough people using dry acid, let alone in large quantities, to know if and when they have problems with their plaster pools. We won't be recommending it given the factual information we have shown you.
 

Enjoying this content?

Support TFP with a donation.

Give Support
Just want to speak up that during the cold water portion of the year, and if you're broadcasting dry acid, and certainly if you have colored plaster, there's some risks of plaster color changes if the dry acid sits directly on the plaster undissolved. MA doesn't have that dissolving problem. So if you continue with dry acid make sure you have a brush handy and move it around. It's amazing how quick it can color damage sensitive plaster.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply