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Thread: Chlorine Demand Problem with Salt Water Pool

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    jkaba's Avatar
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    Post Chlorine Demand Problem with Salt Water Pool

    I've been a pool owner for 20 years, but just switched to salt water this year. Only had Chlorine Demand issues a couple of times during those 20 years, and both times I drained my pool down and double or triple shocked my pool with Cal Hypo. Since I rarely had an issue the last few years, I let my guard down, and did not test my pool very often, and had my SWG set to 30%. I left town for a week in June, and returned to a cloudy pool. In the past I have relied heavily on the pool stores tests, and have bought a few of my chemicals there to keep them happy, however this year they are charging for the tests and are not very cooperative in that they refused to do a chlorine demand test for me. That is the only store in our town that does testing so I searched online and found this forum. I ordered the TF-100 test kit today, and am debating what steps to take in the meantime. Here are my numbers from water tests performed at the pool store.

    6/26 - Came home and pool was cloudy. Could barely see bottom in 3 ft. area.
    CYA: not tested
    FC: 0
    CC: .1
    PH: 8.3
    CH: 329
    TA: 143
    Actions taken: Acid to bring down TA and PH. Set SWG to Superchlorinate. Added a few ounces of clarifier. Added a half bottle of Algecide because of all the rain we had the week we were away.

    6/30 - Clarity of water was better, but still not seeing bottom in deep end.
    CYA: 103
    FC: 0
    CC: .1
    PH: 7.3
    CH: 365
    TA: 109
    Actions taken: 3 lbs Cal Hypo. then waited a few hrs, then 2 gal. bleach, and kept SWG set on Superchlorinate. Added more clarifier and SparkleUp(flocking agent) next day. Couple ounces of Algecide added.

    7/2 - Can now see bottom of pool in the deep end, but water lacks clarity and luster(dull)
    CYA: not tested
    FC: 0
    CC: .1
    PH: 7.8
    CH: 340
    TA: 149
    Phophates were tested and found to be 500
    Actions taken : More acid to bring down TA and PH, and Put in 1 liter Phosfree. Shocked with 5 lbs Cal Hypo, waited a few hrs, then added couple more gallons of bleach, and SWG set to 100%.

    Today - Water is clear, but each of the times we vacuumed the pool, we noticed a dirty film on the liner which may have been algae. Looks like a film of dirt. Not as much residue on the bottom as we have noticed from the previous few times, but still not holding chlorine. Noticed CYA really high, which probably explains why I haven't reached chlorine breakpoint?
    CYA:131
    FC: 0
    CC: .1
    PH: 8.1
    CH: 339
    TA: 154
    They also gave me a Saturation index of .9 (haven't researched this to know what that is all about)
    Actions taken: Added acid to bring down TA and PH. Now waiting to hear from all of you experienced people to give suggestions. Was thinking of a partial drain. Maybe 1/3 then shock with 10 gallons of bleach???? Any other suggestions ideas.
    25k gal, 18' x 36' inground vinyl pool, 1HP Hayward Super II Pump, Hayward S244T Sand Filter, Hayward H200 Pool Heater, Circupool Si30 SWG, Polaris 380 cleaner, TF-100 Test Kit.

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    Mod Squad jblizzle's Avatar
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    Re: Chlorine Demand Problem with Salt Water Pool

    Welcome to TFP!

    Your CYA is much too high, so you likely need to replace some water ... although verify with your TF-100 (great choice).

    We never recommend adding an arbitrary amount of chlorine. Always test and use PoolMath. You will need to follow the SLAM process (see how to in Pool School) to clear up the pool using bleach, not the SWG. You should never need to use clarifier or algaecide.
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    jkaba's Avatar
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    Re: Chlorine Demand Problem with Salt Water Pool

    Does it seem plausible for the CYA to climb from 103 to 131 from just the few bags of Cal Hypo?
    25k gal, 18' x 36' inground vinyl pool, 1HP Hayward Super II Pump, Hayward S244T Sand Filter, Hayward H200 Pool Heater, Circupool Si30 SWG, Polaris 380 cleaner, TF-100 Test Kit.

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    Re: Chlorine Demand Problem with Salt Water Pool

    Cal-hypo doesn't raise CYA, it raises Calcium Hardness. Trichlor and Dichlor raise CYA.
    John
    7 year old ~13,500 gal 24' AGP with 1.5 hp Proline pump, 150 sqft Pleatco cartridge, filled with well water with pH of about 4.5.
    Wanda the Whale pool vacuum, home made heater, Taylor K-2006
    Cloudy Pool? 1) Order test kit. 2) Follow SLAM
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    JasonLion's Avatar
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    Re: Chlorine Demand Problem with Salt Water Pool

    That change is probably a testing problem. None of the available CYA tests are precise enough to distinguish those two levels from each other. Digital testers are especially deceptive, giving three digit results that are actually +-20 or worse.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    jkaba's Avatar
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    Re: Chlorine Demand Problem with Salt Water Pool

    How accurate is the TF-100 CYA test? Will it have the same degree of error as the pool store?
    25k gal, 18' x 36' inground vinyl pool, 1HP Hayward Super II Pump, Hayward S244T Sand Filter, Hayward H200 Pool Heater, Circupool Si30 SWG, Polaris 380 cleaner, TF-100 Test Kit.

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    JasonLion's Avatar
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    Re: Chlorine Demand Problem with Salt Water Pool

    The CYA test is +-15 (a little better once you have a lot of experience with it). Pool stores vary, but many are much worse than that.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    jmcdtucson's Avatar
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    Re: Chlorine Demand Problem with Salt Water Pool

    So for a test that is +-15, does it make sense to do 3 tests and take the average?
    Intex 12'x24'x52"
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    Re: Chlorine Demand Problem with Salt Water Pool

    It will make more sense to try the test by the instructions first. If you see you are at or around 100, add 50% tap water to your pool water, run the test again, then double the result. You may be well over 100. CYA tests get very unreliable when the content is over 100ppm. With a SWG, luckily you may not have to replace a whole lot of water, I'd shoot for 70ppm CYA.

    Here's the issue, if CYA is sky high, you will almost positively not have enough FC in the water to keep it sanitary, and probably won't be able to maintain a very high FC with a SWG.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    Re: Chlorine Demand Problem with Salt Water Pool

    I was where you are about a month ago. My CYA was around 100 and I couldn't keep the pool clear. I had gotten lazy and used Trichlor pucks over the winter, resulting in my high CYA. The Pool Store kept telling me my Cl was high, yet I kept getting algae growth in between random shocks. I found TFP, lowered my CYA and was able to clear up the pool with a single night of SLAMming. I haven't looked back, keeping my daily doses of CL added to the pool until I installed my SWG 2 weeks ago. The takeaway from that was CYA=100+ is a back breaker. It was expensive to try to keep pace and it proved impossible without a good test kit and TFP. Stick with it, and you will get there too.
    16x32 DiamondBrite kidney, 12,500 gal. (circa 1985) 3/4hp Hayward SII, Harmsco BF84, Taylor K-2006, Hayward SwimPure Plus / Tcell-15
    Boca Roton, Fl. USA.

    prior 17k gal. vinyl, Sand filter

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    jkaba's Avatar
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    Re: Chlorine Demand Problem with Salt Water Pool

    Ok, I received my test kit yesterday and initial tests showed

    CYA 80
    FC 2.0
    CC 1.5
    TA 160
    CH High(700) Source water is high(maybe 400)

    I was concerned with the CYA at 80 and wanted to reduce it, so vacuumed algae and leaves to waste, and dropped it about 8", refilled, added salt, and a little acid(source water has a higher ph), tested again this morning and new results are:

    CYA 70-80
    FC 1.5
    CC 1.5
    TA 160
    PH 7.2 -7.5 maybe 7.3? Using TF-100 kit, and color match scale jumps from 7.2-7.5 (reads closer to 7.2)

    Planning on Slamming today using 9 gallons of 8.25% bleach as per Pool Math and the tables for the SWG shock for a CYA of 80. Does this sound like a good plan?
    25k gal, 18' x 36' inground vinyl pool, 1HP Hayward Super II Pump, Hayward S244T Sand Filter, Hayward H200 Pool Heater, Circupool Si30 SWG, Polaris 380 cleaner, TF-100 Test Kit.

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    Mod Squad jblizzle's Avatar
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    Re: Chlorine Demand Problem with Salt Water Pool

    With the visible algae and the high CC, you certainly need to follow the SLAM process. Your FC will be a bit higher due to the higher CYA levels, but should be doable.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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