Hi,
Some background: I’m a newish member of about 3 weeks and still trying to figure out the best area to post various questions. So far, in a couple other threads, I’ve had discussions relating to algae control in my high CYA pool, and I was strongly advised to change my water rather than attempt to control the algae while my CYA drops over time. (I recently cancelled my pool service and switched from trichlor to LC, hoping to avoid a water exchange while waiting for my CYA to come down.) I have since scheduled an RO purification after spending a few more days (successfully I think) fending off another algae attack, and decided that I don’t want to spend my summer doing that. Now I plan to maintain a higher FC (targeting 10-12) according to the FC/CYA Chart, hoping to prevent additional algae growth until my RO treatment in about 2 weeks. Actually since the FC/CYA chart stops at CYA 100, I am going by a relationship that I think I saw on this site which is to ensure a minimum FC that never drops below 7.5% of CYA level. I had also planned to add some polyquat algaecide but was talked out of that on this forum.
My question: What I am wondering at this point is why my CH seems to be increasing while my CYA is decreasing as I dilute the pool water. I have been performing my own tests with the K-2006 test kit. I have been backwashing more frequently over the past 2 weeks and refilling with water from my household water softener, and we have had some rain. During that time, which included 3 complete test cycles (plus interim tests of FC/pH/TA, my CYA has decreased from 210 to 129, but calcium hardness has increased from 440 to 575. The reason I’d like to understand this is because after the RO treatment is completed, I’m expecting that by sticking with TFP methods I will be able to easily keep my CSI within limits and never again have to deal with any calcium ring on my tile (which I currently have a very strong one). This rising CH makes me concerned that there might be something else going on that I haven’t learned about yet.
It is possible that my early CH tests had higher measurement errors due to my learning curve, but I am pretty confident that my CYA has come down by at least 50 ppm and CH is not decreasing at all but might be increasing. For my first 2 CH tests I may have stopped titrating too soon while the color was still purple. I stopped when the color stayed purple and did not change after adding additional drops. Then I subtracted those extra drops that did not further change the color. I used a 25 ml sample the first week but then switched to a 10 ml sample to conserve my reagent. When I tested today I swirled a little longer between each drop (more so than the FC test) and the color was fully blue. So possibly my earlier test results were too low?
One thing that I did do a few days ago to fend off the algae bloom mentioned above (because I had let my FC drop too low) was I added Green to Clean to my pool. I did not use cal-hypo for the shock, I used LC. Other than that, I have used nothing but LC and MA in my pool since taking over from the pool company. Is it possible that the Green to Clean may have caused CH to increase, or prevented it from being diluted as the CYA was? My understanding was that the GTC it would create chloramines but not affect the pool balance. The pool was slightly cloudy (white cloudy not green) the first day after application and today it is clear.
I did also test my tap water using the K-2006 reagents and result was <25ppm. I took the tap water sample from my kitchen sink and not the hose bib that is actually connected to the pool.
Does it seem like my CH should have come down more?
Test cycle 1 (June 18):
CYA 210 (1:3 dilution)
FC 10 (10 ml sample size)
CC .5
pH 7.8
TA 175 (10 ml sample size)
CH 420 (25 ml sample size) may have stopped titrating when sample was still purple
After this test cycle, I added LC and MA several times and backwashed once prior to the next full test
Test cycle 2 (June 24)
CYA 195 (1:3 dilution)
FC 4.5 (10 ml sample)
CC 0
pH 7.8
TA 150 (10 ml sample size)
CH 500 (switched to 10 ml sample size) may have stopped titrating when sample was still purple
Sodium 610 (used titration strip to get baseline for CSI tracking)
After this test, I added LC and MA several times, backwashed 2-3 times and it rained
Green to Clean added on June 26 after low FC triggered algae growth
Test cycle 3 (June 29)
CYA 129-150 (1:3 dilution) I repeated the pour/dot reading 3 times with the same mixture and got: 43, 50, and 43 drops multiplied by 3
FC 13
CC 0
pH not measured due to high FC
TA 160 (used full 25 ml sample to improve accuracy)
CH 575 (10 ml sample) titrated until test sample was fully blue
Sodium (titration strip) 930
Some background: I’m a newish member of about 3 weeks and still trying to figure out the best area to post various questions. So far, in a couple other threads, I’ve had discussions relating to algae control in my high CYA pool, and I was strongly advised to change my water rather than attempt to control the algae while my CYA drops over time. (I recently cancelled my pool service and switched from trichlor to LC, hoping to avoid a water exchange while waiting for my CYA to come down.) I have since scheduled an RO purification after spending a few more days (successfully I think) fending off another algae attack, and decided that I don’t want to spend my summer doing that. Now I plan to maintain a higher FC (targeting 10-12) according to the FC/CYA Chart, hoping to prevent additional algae growth until my RO treatment in about 2 weeks. Actually since the FC/CYA chart stops at CYA 100, I am going by a relationship that I think I saw on this site which is to ensure a minimum FC that never drops below 7.5% of CYA level. I had also planned to add some polyquat algaecide but was talked out of that on this forum.
My question: What I am wondering at this point is why my CH seems to be increasing while my CYA is decreasing as I dilute the pool water. I have been performing my own tests with the K-2006 test kit. I have been backwashing more frequently over the past 2 weeks and refilling with water from my household water softener, and we have had some rain. During that time, which included 3 complete test cycles (plus interim tests of FC/pH/TA, my CYA has decreased from 210 to 129, but calcium hardness has increased from 440 to 575. The reason I’d like to understand this is because after the RO treatment is completed, I’m expecting that by sticking with TFP methods I will be able to easily keep my CSI within limits and never again have to deal with any calcium ring on my tile (which I currently have a very strong one). This rising CH makes me concerned that there might be something else going on that I haven’t learned about yet.
It is possible that my early CH tests had higher measurement errors due to my learning curve, but I am pretty confident that my CYA has come down by at least 50 ppm and CH is not decreasing at all but might be increasing. For my first 2 CH tests I may have stopped titrating too soon while the color was still purple. I stopped when the color stayed purple and did not change after adding additional drops. Then I subtracted those extra drops that did not further change the color. I used a 25 ml sample the first week but then switched to a 10 ml sample to conserve my reagent. When I tested today I swirled a little longer between each drop (more so than the FC test) and the color was fully blue. So possibly my earlier test results were too low?
One thing that I did do a few days ago to fend off the algae bloom mentioned above (because I had let my FC drop too low) was I added Green to Clean to my pool. I did not use cal-hypo for the shock, I used LC. Other than that, I have used nothing but LC and MA in my pool since taking over from the pool company. Is it possible that the Green to Clean may have caused CH to increase, or prevented it from being diluted as the CYA was? My understanding was that the GTC it would create chloramines but not affect the pool balance. The pool was slightly cloudy (white cloudy not green) the first day after application and today it is clear.
I did also test my tap water using the K-2006 reagents and result was <25ppm. I took the tap water sample from my kitchen sink and not the hose bib that is actually connected to the pool.
Does it seem like my CH should have come down more?
Test cycle 1 (June 18):
CYA 210 (1:3 dilution)
FC 10 (10 ml sample size)
CC .5
pH 7.8
TA 175 (10 ml sample size)
CH 420 (25 ml sample size) may have stopped titrating when sample was still purple
After this test cycle, I added LC and MA several times and backwashed once prior to the next full test
Test cycle 2 (June 24)
CYA 195 (1:3 dilution)
FC 4.5 (10 ml sample)
CC 0
pH 7.8
TA 150 (10 ml sample size)
CH 500 (switched to 10 ml sample size) may have stopped titrating when sample was still purple
Sodium 610 (used titration strip to get baseline for CSI tracking)
After this test, I added LC and MA several times, backwashed 2-3 times and it rained
Green to Clean added on June 26 after low FC triggered algae growth
Test cycle 3 (June 29)
CYA 129-150 (1:3 dilution) I repeated the pour/dot reading 3 times with the same mixture and got: 43, 50, and 43 drops multiplied by 3
FC 13
CC 0
pH not measured due to high FC
TA 160 (used full 25 ml sample to improve accuracy)
CH 575 (10 ml sample) titrated until test sample was fully blue
Sodium (titration strip) 930
