Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 11 of 11

Thread: Is Dry Acid bad for the plaster?

  1. Back To Top    #1

    Join Date
    Jul 2014
    Location
    Berks County, PA
    Posts
    206

    Is Dry Acid bad for the plaster?

    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.
    12,000 gal. Anthony IG pool; 3 ft. shallow end to 6 ft. deep end; Built 1989; Renovated July 2014 using a 10-part unexposed quartz plaster aggregate of 3 S-grade Blue, 3 S-grade Gray, 2 T-grade Blue, 2 T-grade Gray; Apollo VA-52 DE Filter; Hayward SP-2607X10 Super Pump 1-HP Single Speed; Jandy AE-Ti Heat Pump; Taylor K-2006 Test Kit

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Is Dry Acid bad for the plaster?

    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.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Is Dry Acid bad for the plaster?

    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  4. Back To Top    #4

    Join Date
    Jul 2014
    Location
    Berks County, PA
    Posts
    206

    Re: Is Dry Acid bad for the plaster?

    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.
    12,000 gal. Anthony IG pool; 3 ft. shallow end to 6 ft. deep end; Built 1989; Renovated July 2014 using a 10-part unexposed quartz plaster aggregate of 3 S-grade Blue, 3 S-grade Gray, 2 T-grade Blue, 2 T-grade Gray; Apollo VA-52 DE Filter; Hayward SP-2607X10 Super Pump 1-HP Single Speed; Jandy AE-Ti Heat Pump; Taylor K-2006 Test Kit

  5. Back To Top    #5

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Is Dry Acid bad for the plaster?

    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.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  6. Back To Top    #6

    Join Date
    Jul 2014
    Location
    Berks County, PA
    Posts
    206

    Re: Is Dry Acid bad for the plaster?

    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 - - -

    Quote Originally Posted by JasonLion View Post
    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.
    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?
    12,000 gal. Anthony IG pool; 3 ft. shallow end to 6 ft. deep end; Built 1989; Renovated July 2014 using a 10-part unexposed quartz plaster aggregate of 3 S-grade Blue, 3 S-grade Gray, 2 T-grade Blue, 2 T-grade Gray; Apollo VA-52 DE Filter; Hayward SP-2607X10 Super Pump 1-HP Single Speed; Jandy AE-Ti Heat Pump; Taylor K-2006 Test Kit

  7. Back To Top    #7
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Is Dry Acid bad for the plaster?

    I don't know specific levels. People having problems don't tend to have a sulfate test handy.

    What is wrong with using muriatic acid? It is dramatically less expensive.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  8. Back To Top    #8

    Join Date
    Jul 2014
    Location
    Berks County, PA
    Posts
    206

    Re: Is Dry Acid bad for the plaster?

    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.
    12,000 gal. Anthony IG pool; 3 ft. shallow end to 6 ft. deep end; Built 1989; Renovated July 2014 using a 10-part unexposed quartz plaster aggregate of 3 S-grade Blue, 3 S-grade Gray, 2 T-grade Blue, 2 T-grade Gray; Apollo VA-52 DE Filter; Hayward SP-2607X10 Super Pump 1-HP Single Speed; Jandy AE-Ti Heat Pump; Taylor K-2006 Test Kit

  9. Back To Top    #9

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Is Dry Acid bad for the plaster?

    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.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  10. Back To Top    #10

    Join Date
    Jul 2014
    Location
    Berks County, PA
    Posts
    206

    Re: Is Dry Acid bad for the plaster?

    Hi chem geek,

    Thanks for the additional info. Hopefully I will not encounter any problems, and that the pH will begin to stabilize as the plaster cures.
    12,000 gal. Anthony IG pool; 3 ft. shallow end to 6 ft. deep end; Built 1989; Renovated July 2014 using a 10-part unexposed quartz plaster aggregate of 3 S-grade Blue, 3 S-grade Gray, 2 T-grade Blue, 2 T-grade Gray; Apollo VA-52 DE Filter; Hayward SP-2607X10 Super Pump 1-HP Single Speed; Jandy AE-Ti Heat Pump; Taylor K-2006 Test Kit

  11. Back To Top    #11
    gtemkin's Avatar
    Join Date
    Jun 2008
    Location
    Seattle, WA
    Posts
    738

    Re: Is Dry Acid bad for the plaster?

    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.
    21K gal 16' x 40' in-ground pool built 1959, old school with Jacuzzi bronze pump, American Products 24" Sand Filter & Americana Multiport valve, Jandy Lite2 millivolt heater, Coverstar cover, and classic Kreepy Krauly.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •