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State Regulation and Government health agencies have identified UV as the best available technology and are mandating UV on some commercial pool applications. Science has proven UV will destroy far more than Chlorine, Salt chlorine generators and Ozone combined, with a light bulb! Not only will it not harm the surface of the pool…it will prolong the life of the pool and equipment regardless of the materials used in construction!
On new fresh plaster, the effect seems significant. New fresh plaster coupons were placed in slightly positive SI (+.2) water, one day later 3000 ppm of salt was added to several tanks, the pH of the water was tested the next day and rose higher (about .5 pH units) when compared to non-salt water tanks at different starting alkalinity levels. These water tanks would also require more acid to lower the pH back to the starting pH of 7.6. Again, after another day, the pH of this salt water would rise again higher than its non-salt counterpart. Extra acid would be required to lower the pH again. This trend continued for about 7 to 10 days, although the difference in pH rise would decrease and be only slightly higher each day. The extra acid added would require replenishment with baking soda to maintain the starting level and balance.
A bi-product of cement hydration is calcium hydroxide, so it appears that the high salt content seems to be able to dissolve this compound (at least the hydroxide portion) and effect the pH dramatically. After two or four weeks time, calcium hydroxide on the plaster surface becomes carbonated and changes into calcium carbonate, which then appears that the salt doesn't seems to effect it very much.
My long term experiment (eighteen months) comparison on cured plaster coupons didn’t provide very distinguishable results. The non-salt water tanks were maintained in slightly positive water (SI of +.2 to +.5), and using SI adjusted numbers for salt water (3000 ppm) tanks would mean that the SI for them would have been about 0.0 to +.3, so all would have been balanced or on the positive side. There was no discernable difference in the pH readings over the eighteen month period and there was no difference or change in calcium levels. Yet I did note an increase in the alkalinity (20 ppm) in the salt water tanks.
My conclusion is that I need to perform these experiments again, this time making a LSI adjustment towards the aggressive side. But the above results does seems to confirm the need to wait a few weeks before putting the salt in the pool water and starting the SWG unit. Comments are welcomed.
Also from the book POOL SURFACES: PROBLEMS AND SOLUTIONS (7'th Edition) put together by Randy Dukes, a nationallly recognized expert on pool plaster (available at www.poolfinishes.net). Chapter 15 on Pool Start-Up Procedures adresses salt water generators (page 101) it talks about waiting to add salt for 28 - 45 days.
Frank H. Goldstein said:
Bruce Hudson said:
I just could not let your post go unanswered! My experience is that the damage the industry is experiencing is mostly with the natural stone products (coping, decks, underwater rocks, rock waterline, etc.)
When frostproof tile, fired brick, topped and sealed concrete are used, there is little to no damage from salt systems. in such an install, SWG is problem solver, not a problem.
To take this idea to the extreme, we maintained quite a few seawater pools in So. Fl. Stainless steel ladders took some damage at the waterline, and SST filters were not used on these pools. In every other way the pool faired well. Looking at them, one would not suspect that these pools were filled with other than fresh water
SWG is not a good sell on all pools. Unfortunately it's the high-end pools that are normally the worst candidates because of the stone that is so popular with this level of customer. Ozone is a nice fit here.
I am a big fan of SWG and sell it every chance I get, provided the environment is right.