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  Bill Payne November 8, 2011 at 7:42am

  Thanks
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  Richard A. Falk November 3, 2011 at 6:08pm

  "The previous pool service recommended converting this gunite pool to salt to control heavy calcium buildup, explaining that it is the same principal as a water softener."

   

  Really?  Are they joking?  A water softener exchanges sodium ions for calcium ions (and other ions such as magnesium) so reduces water hardness.  This is done via an ion exchange resin.  Simply adding salt (sodium chloride) to a pool high in hardness is not going to reduce that hardness at all.  The previous pool service didn't know what they were talking about.  It is true that with a LOT of salt, the calcite saturation index is reduced somewhat so could slightly reduce scaling, but we're talking about a drop of 0.2 in the index going from a Total Dissolved Solids (TDS) level of 500 to 3000 ppm.  However, a saltwater chlorine generator tends to make the pH rise over time and a higher pH causes more scaling.

   

  If one has high CH and is unable to lower it via water dilution, then one can lower the TA level and target a somewhat lower pH in order to prevent scaling.  Or in extreme cases, one can use a metal sequestrant designed to reduce effective calcium levels and to inhibit scaling.

   

  Calcium buildup is occurring either from the use of Cal-Hypo or from evaporation and refill with water at least moderately high in Calcium Hardness (CH).  With evaporation and refill, whatever CH that is in the fill water gets added to the pool.  Only dilution with water that is lower in CH can reduce its level (evaporation does not dilute the water since only water evaporates, not calcium).

   

  ALL sources of chlorine will increase the salt level.  For every 10 ppm Free Chlorine (FC) added by ANY source of chlorine, it will increase salt by 8 ppm when that chlorine gets consumed/used because chlorine gets converted to chloride.  For chlorinating liquid and bleach (sodium hypochorite), an additional 8 ppm salt is added upon addition so the total is around 17 ppm salt from every 10 ppm FC.  If the daily FC usage is 2 ppm, then this is an increase in salt of around 100 ppm per month if there is no water dilution.
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    Jeff Gale > Richard A. Falk March 13, 2012 at 9:35am

    I have had several pools with salt chlorine generators in plaster pools end up with a very abrasive surface very similar to 20 grit sand paper.  Does anyone know what factors create this issue?  Not all pools with the Salt Chlorine Generators have this issue.  I've seen it mostly on plaster pools but I did have one vinyl liner pool that had a similar situation.  

    I would really like to understand what this is, what the cause of it is, how to remove it, and mainly how to prevent it.

    I tried an acid wash which had no effect and it doesn't dissolve in water either. 
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      Richard A. Falk > Jeff Gale March 13, 2012 at 11:29pm

      Does the plaster appear to be deteriorating so is becoming pitted?  The higher salt level increases TDS and lowers the Calcite Saturation Index by about 0.2.  Also, the higher CYA level of around 80 ppm usually recommended for SWCG pools lowers this index by another 0.1-0.2 depending on the CYA level normally used for a non-SWCG pool.  Also, SWCG pools typically rise in pH more and lowering the TA level can help prevent that, but a lower TA also lowers the saturation index even more.  All of this can be readily compensated by having a higher Calcium Hardness (CH) level.  I suggest you plug in your accurately measured numbers (use a Taylor K-2006 test kit or equivalent) into The Pool Calculator to calculate the saturation index to see if it is strongly negative.
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      Bill Payne > Jeff Gale March 13, 2012 at 8:40pm

      Have you checked for high Alkalinity?
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  Rob M November 2, 2011 at 8:58pm

  Also, ask him if he has been using liquid bleach (sodium hypochlorite). If you use it for a long enough period of time without dilution (year round pool with a cartridge filter?) That could easily happen.
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  Rob M November 2, 2011 at 8:56pm

  here you go:

  http://www.taylortechnologies.com/products_kitinfo.asp?&MarketI...

  1 drop=200ppm NaCl