freeradical Posted June 4, 2010 Report Share Posted June 4, 2010 Hello, I have had stable values for pH/TA for about a week and a half in a 500g spa. Last night's values follow: T set at 97 pH 7.5 (range has been 7.5/7.6, possibly due to interpreter error) TA 50 stable Total Hardness 140 FC 4.0 CC < or 0.5 CYA ~27 ppm (based on 3.36 oz dichlor added since water replacement); have switched to sodium hypochlorite now Borates ~ 48 ppm CSI currently about -0.47 by pool calculator. Should I add more calcium chloride now to improve CSI or just leave it at its current level to help prevent foaming given the spa is fiberglass? Thank you for your help. Quote Link to comment Share on other sites More sharing options...
quantumchromodynamics Posted June 4, 2010 Report Share Posted June 4, 2010 You list "Total Hardness"; you should measure and report "Calcium Hardness". You should not make any adjustment until you measure calcium hardness. My recommendation would be to raise the pH to 7.7 to 7.8 to increase the CSI instead of raising the calcium. Quote Link to comment Share on other sites More sharing options...
polyvue Posted June 6, 2010 Report Share Posted June 6, 2010 T set at 97 pH 7.5 (range has been 7.5/7.6, possibly due to interpreter error) TA 50 stable Total Hardness 140 FC 4.0 CC < or 0.5 CYA ~27 ppm (based on 3.36 oz dichlor added since water replacement); have switched to sodium hypochlorite now Borates ~ 48 ppm CSI currently about -0.47 by pool calculator. Should I add more calcium chloride now to improve CSI or just leave it at its current level to help prevent foaming given the spa is fiberglass? When I ran your numbers via the Pool Calculator and assumed 2/3 of the Total Hardness to be Calcium Hardness (94 ppm) the CSI reports -.62 I don't have useful experience tweaking fiberglass spa chemistry but it seems evident that in addition to increasing pH level to 7.8 or so, a modest increase to calcium may be beneficial. I'd probably increase alkalinity from 50 to 60 ppm and add a couple of ounces of calcium chloride to raise CH from 94 ppm (est.) to 120 ppm. But perhaps QCD and other spa owners here feel that the CSI is best left in negative territory and TA very low in order to keep pH stable. Quote Link to comment Share on other sites More sharing options...
freeradical Posted June 6, 2010 Author Report Share Posted June 6, 2010 T set at 97 pH 7.5 (range has been 7.5/7.6, possibly due to interpreter error) TA 50 stable Total Hardness 140 FC 4.0 CC < or 0.5 CYA ~27 ppm (based on 3.36 oz dichlor added since water replacement); have switched to sodium hypochlorite now Borates ~ 48 ppm CSI currently about -0.47 by pool calculator. Should I add more calcium chloride now to improve CSI or just leave it at its current level to help prevent foaming given the spa is fiberglass? When I ran your numbers via the Pool Calculator and assumed 2/3 of the Total Hardness to be Calcium Hardness (94 ppm) the CSI reports -.62 I don't have useful experience tweaking fiberglass spa chemistry but it seems evident that in addition to increasing pH level to 7.8 or so, a modest increase to calcium may be beneficial. I'd probably increase alkalinity from 50 to 60 ppm and add a couple of ounces of calcium chloride to raise CH from 94 ppm (est.) to 120 ppm. But perhaps QCD and other spa owners here feel that the CSI is best left in negative territory and TA very low in order to keep pH stable. Quote Link to comment Share on other sites More sharing options...
freeradical Posted June 6, 2010 Author Report Share Posted June 6, 2010 Correction and update: Should have stated calcium hardness=140 ppm and not total hardness. Current values: T 96.8 pH 7.7 TA 70 FC 2.0 CC 0 Borates 48 CSI -0.12 Parameters appear better to me. Is pH of 7.7 OK? My manual suggests 7.4 to 7.6 range. Since I occasionally use MPS prior to longer soaks, pH will likely drop anyway requiring periodic alkalinity adjustments. How soon after adding sodium hypochlorite do you recheck to FC level to make sure that pool calculator did not over or underestimate the required amount? Quote Link to comment Share on other sites More sharing options...
quantumchromodynamics Posted June 6, 2010 Report Share Posted June 6, 2010 Your numbers look good. I wouldn't raise the calcium higher than 140. I like to keep the pH between 7.5 and 7.9. After adding sodium hypochlorite, you can check within a few minutes if the circulation is good. I would keep the CSI between -0.25 and 0.0. Quote Link to comment Share on other sites More sharing options...
freeradical Posted June 7, 2010 Author Report Share Posted June 7, 2010 Thank you for all the feedback. Quote Link to comment Share on other sites More sharing options...
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