simonc Posted March 15, 2010 Report Share Posted March 15, 2010 I was balancing my water and needed to raise my CH from 80 to 180 to achieve a near zero on the CSI. (My TA is 70. pH usually in the 7.4 - 7.6 range.) I used the pool calculator and found that I needed 5 oz. (by weight) of calcium. I got out my scale, weighed out 5 oz. and then, in two installments, added it to my tub. (Yes, I probably should have measured my CH after the first dose, but I didn't. How could the pool calculator be wrong?) Anyway, my CH is now 240. How can I lower it? The pool calculator recommends removing water and then replacing it with zero CH water. I don't have zero CH water so my guess is that I would have to remove 1/2 of my water to achieve a CH of about 180. Also, I would then have to rebalance everything again. No fun and a lot of use of expensive Taylor reagents. So ... Can I add some "Stain and Scale Inhibitor" to lower the CH? The container says it contains 10% polyphosphonic acid ... whatever that is. If so, how much should I add to bring CH down to the 180 level? (I have a 275 gallon tub.) I know I can lower my TA to "balance" the high CH. I usually keep my TA at about 70 or 80. If I lower it too much I'm afraid I'll have problems with pH fluctuation. Any other suggestions? Thanks, - Simon Quote Link to comment Share on other sites More sharing options...
chem geek Posted March 15, 2010 Report Share Posted March 15, 2010 You aren't so much over to worry about it. I'd just leave it as. Perhaps you put in "calcium chloride dihydrate" in the pool calculator, but in fact used calcium chloride anhydrous and therefore overdosed. Either that, or there was some measurement error in the before and after CH tests. Again, I wouldn't worry about it. Quote Link to comment Share on other sites More sharing options...
simonc Posted March 15, 2010 Author Report Share Posted March 15, 2010 You aren't so much over to worry about it. I'd just leave it as. Perhaps you put in "calcium chloride dihydrate" in the pool calculator, but in fact used calcium chloride anhydrous and therefore overdosed. Either that, or there was some measurement error in the before and after CH tests. Again, I wouldn't worry about it. Chem Geek - If you say not to worry about it, I won't. I'll re-measure tomorrow and make sure I got my numbers correct. Lastly, I got my directions wrong on the TA. If I want to move my CSI closer to zero, I need to increase my TA, not lower it. I think? I can do this by adding a little baking soda. Tonight I'll soak. Tomorrow, I'll measure and balance, leaving the CH at 240. - Simon Quote Link to comment Share on other sites More sharing options...
chem geek Posted March 15, 2010 Report Share Posted March 15, 2010 You can always keep your TA a little lower if you are concerned about the CSI getting too high. Remember that a higher TA can have the pH rise more quickly over time so keeping it lower is not a bad thing. I wouldn't sweat trying to get close to a CSI of 0. Having it be a little negative in a spa is quite reasonable. Quote Link to comment Share on other sites More sharing options...
quantumchromodynamics Posted March 15, 2010 Report Share Posted March 15, 2010 pH = 7.5 TA = 70 ppm CH = 240 ppm CYA = 40 ppm Borate = 50 ppm Temp. = 104 CSI = -0.06 Your numbers are not too bad as long as you keep your pH under control. However, since it's so easy to do, I think that you should drain and refill to avoid any chance of calcium scaling. Quote Link to comment Share on other sites More sharing options...
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