Q: I was doing some research and found that HEDP shouldn't be used with salt systems because of the formation of orthophosphate (algae food from what I understand). Will I be all right with the phosphonic acid derivative sequestering agent and a salt cell?
A:Jack's Magic the Purple Stuff is made specifically for Salt Water Pools.
http://www.jacksmagic.com/page.cfm?id=372
It does contain HEDP, but it supposedly contains a special proprietary formula for SWCG pools. It's probably part science and part hype. HEDP will eventually break down and you will need to add more.
The conditions inside the cell can get pretty brutal. According to some references the chlorine can reach as high as 50 ppm, the pH can be near 14 or 0 and the temperature can be as high as 120 F
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Q: Also, what's happening with the metal deposits? Am I just "binding" the metals up so they can't stain my plaster? Is there away to eliminate the metals or am I dreaming?
A: Yes, you are just binding or sequestering them. The next step is to get an accurate level for metals in your pool and fill water. You can go to a pool store or a water conditioner/softener business to get metals tested.
For metals in your pool water, you can try to keep them sequestered and/or you can try to get them to precipitate out where you want. You can add a filter (DE, Sand or Cartridge) after the salt cell to help catch oxidized metals that are ready to precipitate out.
For your fill water, consult the water conditioner company for possible solutions
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Q: If they come back in the exact same spot it should be algae......if they come back in different spots its copper deposits, right?
A: Try to get a sample for close examination; algae will be kind of like soft mold. Also, get the copper test for pool and fill water.
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Q: So is the only reason I need CYA in my pool to extend the life of my salt cell?
A: No, that's only one reason, but it's a good one to start. Other reasons include reduced cell scaling, reduced raising of pH due to run time, reduced raising of pH due to cyanuric acid's buffering capacity, reduced raising of pH due to aeration, mitigation of chlorine's effect on people and equipment, stabilization of chlorine levels etc. I highly recommend that you maintain 60 ppm. Recheck levels before buying cyanuric acid.
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Q: Don't I want to keep it 7.5ish to also keep from burning my swimmers eyes? Won't 7.7 sting?
A: No, 7.7 will not irritate eyes. I know that it may seem counter intuitive, but a higher pH will rise less than a lower pH.
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You should consider adding 50 ppm borates to your pool. They will help buffer the pH. Verify that this is OK with whomever you need to before doing this.
If you do add the borates, I recommend using boric acid instead of Borax. The end result is the same but the boric acid is more pH neutral. You can use about 80 to 85 % boric acid and 15 to 20 % Borax if your pH is neutral to low.
http://www.chemistrystore.com/search.cgi?keywords=boric+acid
http://www.proteampoolcare.com/
http://www.lamotte.com/pool_spa_water/pool...ips.html#borate
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Don't be too concerned about orthophosphates as algae food. Yes, they are algae food, but algae can't eat if they're dead. Keep a free chlorine level of about 5 to 8 % of your cyanuric acid level. At 60-ppm cyanuric acid, that is 3 to 4.8 ppm. Algae won't stand a chance.
The biggest problem with phosphate in a SWG pool is that the phosphates tend to form scale more easily than other elements and this base layer of scale will act as the seed crystal for other types of scale such as calcium carbonate.
You should monitor phosphate levels and cell scaling to see if there is a correlation. If you get high levels of phosphates and otherwise unexplained persistent scaling, you may want to consider a phosphate removal product based on Lanthanum.
You may be better off not using a sequestering agent due to the phosphate potential.
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Get the Taylor K-2006 test kit for best results.
http://www.taylortechnologies.com/products...&KitID=2230
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Q: My hot tub is also a SWG, combine that with the air jets and the small size and my PH is always wanting to soar high. I try to keep her as low on the PH as I can (7.2-7.4) because it can rise so fast. Its also plaster, should I keep the PH higher in her?
A: The aeration and high temperatures in a hot tub will cause rapid loss of carbon dioxide. This is what's causing the pH rise. Keeping the pH higher will help reduce pH rise. Adding cyanuric acid to 40 ppm and boron to 50 ppm will also help mitigate pH problems.
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Maintain a Saturation Index as close to zero as possible. Go to http://www.thepoolcalculator.com to calculate your Saturation Index. Be sure to use the right temperature for your pool or hot tub.
Calcium Saturation is inversely proportional to the temperature. The hotter the water, the less calcium and carbon dioxide it can hold.
If your SI is too low, you will dissolve your plaster. If it is too high, you will get scaling in your heaters and salt cells.
High temperatures, high pH and aeration inside the salt cell all increase the likelihood of scaling. Be sure to periodically remove and examine the cell for scaling or wear.
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Always use the purest salt available. There are different grades of salt and some salt can contain a lot of impurities, such as metals and such.
http://www.unitedsalt.com/site/html/p_8368.htm
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How old is this pool?
