Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 12 of 12

Thread: What causes calcium scaling in an old pool.

  1. Back To Top    #1

    Join Date
    Aug 2008
    Location
    Honolulu
    Posts
    429

    What causes calcium scaling in an old pool.

    What causes calcium scaling in an old pool which is properly balanced? Or should that not happen?

    Just wondering.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  2. Back To Top    #2
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: What causes calcium scaling in an old pool.

    Where are you observing the scale?
    Was the pool ALWAYS balance?
    How do you define "properly balanced"? What is the history of the CSI?
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  3. Back To Top    #3

    In the Industry


    Join Date
    Feb 2012
    Location
    Phoenix, AZ
    Posts
    728

    Re: What causes calcium scaling in an old pool.

    High CH (Calcium Hardness) can cause calcium scaling. When you say the pool is 'properly balanced,' what are your test results? Also, a signature box with pool and equipment info would be helpful!

  4. Back To Top    #4
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: What causes calcium scaling in an old pool.

    Scaling has nothing to do with the age of the pool. Scaling is entirely a function of the levels being out of balance.
    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

  5. Back To Top    #5
    Mod Squad zea3's Avatar
    Join Date
    Jul 2009
    Location
    Houston, Texas
    Posts
    9,198

    Re: What causes calcium scaling in an old pool.

    Same thing that causes calcium scale in a new pool, or any pool for that matter. Calcium scale is usually the result of a "perfect storm" type of water chemistry. If you have high calcium levels, say 400 ppm or better and pH above 7.5 and TA over 120 you are at risk of developing calcium scale. High calcium levels can be managed if you keep the pH and TA on the low end of the acceptable range, say 7.2 and 70ppm respectively.

    Bottom line is when the pool is properly balanced there will be no scale formation.
    TFP Moderator
    Helpful links: TF Test Kits,TFP Pool School, PoolMath
    Vogue 21' round AG, Pentair 1 hp 2 speed pump, 36 sq ft DE filter, Hayward S180T 150# sand filter, Houston, Texas
    Love TFP? Become a
    TFP Supporter!

  6. Back To Top    #6
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: What causes calcium scaling in an old pool.

    Would a white ring around the tile be considered "scale" or is it possible that would just be deposits due to evaporation? ... these rings are very common in AZ ... in our toilets for that matter as well.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  7. Back To Top    #7
    Richard320's Avatar
    Join Date
    Jan 2010
    Location
    San Dimas, CA (LA County)
    Posts
    18,768

    Re: What causes calcium scaling in an old pool.

    Quote Originally Posted by jblizzle
    Would a white ring around the tile be considered "scale" or is it possible that would just be deposits due to evaporation? ... these rings are very common in AZ ... in our toilets for that matter as well.
    I'd say more likely evaporation. It is scale, but not like we're usually discussing here. Our scale is usually blue-grey or tan splotches that can end up feeling like sandpaper if left too long.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

  8. Back To Top    #8
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: What causes calcium scaling in an old pool.

    Quote Originally Posted by Richard320
    Quote Originally Posted by jblizzle
    Would a white ring around the tile be considered "scale" or is it possible that would just be deposits due to evaporation? ... these rings are very common in AZ ... in our toilets for that matter as well.
    I'd say more likely evaporation. It is scale, but not like we're usually discussing here. Our scale is usually blue-grey or tan splotches that can end up feeling like sandpaper if left too long.
    OK, that is what I thought and just wanted to confirm ... also the reason I asked the OP about the scale location.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  9. Back To Top    #9

    Join Date
    Aug 2008
    Location
    Honolulu
    Posts
    429

    Re: What causes calcium scaling in an old pool.

    Observing no scale at present but have in the past with lower CyA level of 30 - 35 (for around 15 years or so) although appropriately balanced but perhaps too high a CH level of 600 to acheive a lower pH of 7.3- 7.4, also to low a TA, now CyA 80. Yes I am finally a convert to the higher CyA levels. CSI was normally in the past targeted at -0.15 to -0.22. I think that too high a CH level, combined with a low pH and low TA may have caused my previous issues despite a relatively OK CSI. Any thoughts?

    Here is how I define "properly balanced" at present:

    FC - 7.5 to 8.0 (mustard gas issues in Hawaii)
    pH - 7.7
    TA - 80
    CH - 350
    CyA - 80
    Salt - 3400
    Borates - 0 (Dog)
    Temp - 78 (82 if Grandkids are swimming)
    CSI - -0.16

    Purple Stuff at 12 ppm, 4 oz Algaecide each week. Previously 5 oz Magenta stuff weekly when CyA was 35 and no Algaecide 60.

    10,000 gal plaster pool with two long plaster steps (maximum depth 4ft 6 inches)
    3/4 hp WhisperFlo pump (6 hours or about one turn per day - electricty rates are 32 cents to 35 cents per Kilowatt dependant on oil adjustment)
    Sta-Rite Great White GW9500 pool cleaner (constantly moving when pump is on) (with catcher basket and pool sock in both basket and skimmer cleaned every two days)
    PoolPilot Digital SC-60 with pH/acid control (cleaned per manual weekly)
    Hayward 300 lb Sand Filter (sand changed every 6 years and backwashed every 4 to 6 weeks)
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  10. Back To Top    #10
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: What causes calcium scaling in an old pool.

    Relatively high CH levels allow even very small fluctuations in the PH to result in scaling. It is impossible to completely prevent some PH fluctuation unless you have an automated PH control system. The higher the CH level, the more diligent you need to be about maintaining PH.
    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

  11. Back To Top    #11

    Join Date
    Aug 2008
    Location
    Honolulu
    Posts
    429

    Re: What causes calcium scaling in an old pool.

    JasonLion,

    I certainly agree with you, despite having a pH controller and acid feeder, there were over the course of the 18 hours the pump was off fairly wide pH swings at that time. With that high a CH it is certainly probable in retrospect that this was the cause.

    At present the pH hardly moves at all and only about 1 oz a day of acid is being remitted to the pool, hopefully those days are over.

    The reason I tried the higher CH was to avoid putting as much baking soda as I use to. Also I wanted the pH at 7.4 or below to control iron staining but it seems that the now switched to Purple stuff from the Magenta stuff is keeping that in check. As there is no apparent scaling going on now I think that my staining and scaling issues may, I hope, be behind me.

    With the higher present pH of 7.7 -7.8 I am using about 23 oz of Baking Soda every 3 to 4 days as the TA drops from 80 to 70 but the pH is hardly moving at all and hopefully scaling will not occur.

    Is this drop of 10 ppm of TA in 3 to 4 days normal?

    I do remember reading an article many years ago by the designer of pools for the Olympic Games (not an Olympic size pool designer which I am aware is completely different) where they mentioned that they preferred a pH of 8.0, which would probably mean a lower TA of 60. They felt that this caused less corrosion to both equipment and the pool itself. I wish I saved the article but I did not, if I find it again I will post a link. Pools built for the Olympics are I think tiled so there maybe differences in the approach. Also I am not sure if they lowered the pH for the games themselves. I do remember one other fact I found startling and that was the Chlorine levels for the actual games were very high in the pool itself and extremely high in the pre/post-dip shallow pool, presumably for sanitation purposes. As this article was read some years ago the philosophy may have changed.

    I will stick with my present balance allowing the pH to go to 7.8, the CH to move down to 325, and the TA to move to 70.

    But do you have any thoughts on this designers approach to pH?

    Thank you for your help.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  12. Back To Top    #12
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: What causes calcium scaling in an old pool.

    It is difficult to imagine what they were talking about without more information.

    One large problem with swim competitions is that many people are being very vigorous in the water all at the same time, creating a large spike in chlorine consumption. In the Chinese games they solved this problem by having an extreme circulation system, capable of completely replacing the water in the pool every 15 minutes. That allowed them to recover from the sharp spikes in chlorine usage after each round. Without the extreme circulation system you raise FC very high and hope you still have some left at the end at the end of the day.
    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

Posting Permissions

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