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Thread: Cannot get free chlorine up and combined near zero

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    Cannot get free chlorine up and combined near zero

    Once I discovered the pool store was incorrectly telling me my chlorine levels were high when indeed they were very low, the battle between me and the pool began. Here are my current test results:

    FC - .70ppm
    Combined Chlorine - .97 ppm
    pH - 7.1
    TA - 110
    CYA - 83

    Yesterday I added 32oz by volume of soda ash to increase the pH based on poolcalculator.com. 4 hours later I tested at 7.4 pH. Now my pH is down to 7.1 again. No major storm overnight.

    Last night I added 7 lbs of 65% cal-hypo shock to try to get the FC up to about 20 and eliminate the CC. Prior to shocking the FC was 0.11 and CC of .43. The shocks seems to have done very little from my testing this morning (above). What's up?!!

    BTW, the pool store told me my total and FC were at 5 last week when indeed the total was near 5 and the FC was below 1!! So I have managed to bring the CC down substantially but cannot get it near zero with good FC levels.
    Jeremy
    26,000 gallon IG pool, Hayward DE filter, Hayward Ecostar SP3400VSP, Chlorinator, Polaris 9550 cleaner

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    Mod Squad tim5055's Avatar
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    Re: Cannot get free chlorine up and combined near zero

    Welcome to TFP!

    I have to ask a few questions....

    What are you testing with?

    How are you adding chlorine to the pool?

    How does the water look - clear, sparkles, cloudy, green ?
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Cannot get free chlorine up and combined near zero

    First, welcome to TFP!

    The first question I have is what you are using to get those results? That answer will directly affect the next step.

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    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
    Pool School - PoolMath - HIGHLY Recommended Test Kits

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    Re: Cannot get free chlorine up and combined near zero

    Let me predict the future.... pool store results or test strips? Get a recommended test kit and take your own measurements. It'll be more accurate and you'll easily save the cost of the kit in the reduction of chemicals you "think" you need.
    45'x12' 17k gal, IG plaster, Pool Pilot Nano+ SWG, 1/2hp Whisperflo pump, PAC-FAB TA-60D sand filter, Raypak 266 heater
    Pool School + Test Kit + Pool Math = Trouble Free Pool

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    Re: Cannot get free chlorine up and combined near zero

    The water is clear and sparkling and has been that way since opening. The results are from my own test kit and not test strips or the store. I bought a Sensafe eXact iDrip because I am partially color blind and feel that determining colors on my own was very inaccurate. The Sensafe is created by Industrial Test Systems who has a long history of creating tools for field testing and lab testing. Hence, I trust their results as being very accurate. I also had a different pool store test the water to compare and their results were nearly identical from a waterlink Spin Lab. Test strips have always showed the free chlorine is very low to none and the store shrugged that off saying we don't trust test strips (that they sell with their branding on them). I find it hard to believe that if they are seeing high levels of FC that even inaccurate test strips would be showing the opposite. Anyway, all of this just to say I know everyone here uses TF-100 but while I am not, I am at least using a very precise method.
    Jeremy
    26,000 gallon IG pool, Hayward DE filter, Hayward Ecostar SP3400VSP, Chlorinator, Polaris 9550 cleaner

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    Mod Squad tim5055's Avatar
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    Re: Cannot get free chlorine up and combined near zero

    One of the reasons we support Taylor reagents is that other than the pH test, there is no color matching involved. I can't comment on the accuracy of your testing, but comparing it to a Spin Lab does not make me feel better. I have compared my testing to Spin Lab testing (the closest pool store to me uses a SpinLab) and their numbers have been way off. I'm sure it has something to do with cleaning or calibration of the Spin Lab.

    The solution to your problem is to SLAM the pool. Is is a system of maintaining shock level until testing shows the water is clear.

    Lower your pH to 7.2 & SLAM the pool

    Pool School - SLAM - Shock Level And Maintain
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Cannot get free chlorine up and combined near zero

    Color blindness can make it difficult to use the color based kits. You may want to add in your signature that you are using that and why so we know in the future. As for the precision of the method, well do not confuse precision for accuracy.

    As Tim asked, what are you using to chlorinate your water? Your CYA is rather high as it is, if you are using pucks in a chlorinator then that number will continue to rise. You can see by the Chlorine / CYA Chart that you will need to maintain an FC over 7 at all times to compensate for this high CYA level. On top of that your SLAM level will require you to raise your FC to 32 and maintain it there to clear everything out. How high can your test equipment measure FC to?
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
    Pool School - PoolMath - HIGHLY Recommended Test Kits

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    Re: Cannot get free chlorine up and combined near zero

    That is a very good point. If still using the puck chlorinator I would discontinue and use Pool Math to calculate how much water you need to change to get that down to at least 60, 50 would be better. Only use liquid chlorine going forward or you will be in the same situation quickly.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Cannot get free chlorine up and combined near zero

    Quote Originally Posted by tim5055 View Post
    One of the reasons we support Taylor reagents is that other than the pH test, there is no color matching involved. I can't comment on the accuracy of your testing, but comparing it to a Spin Lab does not make me feel better. I have compared my testing to Spin Lab testing (the closest pool store to me uses a SpinLab) and their numbers have been way off. I'm sure it has something to do with cleaning or calibration of the Spin Lab.

    The solution to your problem is to SLAM the pool. Is is a system of maintaining shock level until testing shows the water is clear.

    Lower your pH to 7.2 & SLAM the pool

    Pool School - SLAM - Shock Level And Maintain

    I get that these devices need calibration regularly. Please do not take this the wrong way... My device is brand new and calibrated by the manufacturer. If both devices were out of calibration then how could the results be nearly identical? Understand too that the eXact iDrip is an EPA approved testing device. It uses small exact strips of reagants rather than other methods which rely on the user to measure drops. I'm not putting down the methods that are discussed here as a preference but just noting that these electronic methods are leveraging mechanisms that are far more accurate than any human can ever be.

    Back to the problem at hand. The water is very clear. There is no visible algae or discoloration. The poolcalculator.com recommended taking the FC level to 22 which is why I added the calculated amount of 7 lbs of shock.

    3 questions:
    How long and how much shocking?
    How is it possible that I added 7 lbs last night and the FC measurement was under 1 and nearly 0 this morning?
    Why is the pH fluctuating?

    - - - Updated - - -

    Quote Originally Posted by Donldson View Post
    As Tim asked, what are you using to chlorinate your water?
    I have a hayward chlorinator with 3" pucks. Adding liquid chlorine on an ongoing basis seems labor intensive and expensive. Am I wrong? What about an SWG? Does that raise CYA?
    Jeremy
    26,000 gallon IG pool, Hayward DE filter, Hayward Ecostar SP3400VSP, Chlorinator, Polaris 9550 cleaner

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    Re: Cannot get free chlorine up and combined near zero

    Well, if your CYA is 83 your shock level is really somewhere between 31 & 35, not 22.

    I have to ask again, how are you chlorinating your pool. If you continue to use the tabs and granular shock, which your addition of 7 pounds tells me you are doing you are changing the numbers while you work. We recommend sticking with liquid chlorine when conducting a SLAM, and in your case with high CYA I would have recommended a partial drain and refill before you started to get the CYA down to a reasonable number.

    As to the pH, I know the Taylor reagents are affected by high chlorine. Not knowing your device leaves me at a disadvantage to answer that question.

    As to the how much and how long, did you look,at the link to the SLAM in my post above? It is very specific as to both.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Cannot get free chlorine up and combined near zero

    Jeremy, I'll chime in if you don't mind with my 2-cents. You appear to have a fondness for the sensafe tester. I don't think anyone wants to dismiss the efforts you are applying in trying get accurate results, just remember that the Poolmath Calculator and all the TFP methodology is based on the accuracy of those readings - primarily from a TF-100 or Taylor K2006. Aside from that ... we press on right? To answer your last 3 questions:
    - Remember in TFP we don't "shock" like the pool stores - we SLAM. So you will SLAM until you meet the 3 criteria noted on the SLAM page (link below). How well the SLAM works is 100% dependent upon the accuracy of the FC and CYA readings.
    - As for your FC question ... can you please confirm exactly "what" product you added (7 pounds) last night? If it was a type of power, 7lb (112 oz) should shoot FC from 0 to over 60ppm. Am I misinterpreting your note?
    - Also note that when the FC is raised significantly (i.e. during SLAM), the PH readings will be slewed. SLAM states to "start" at PH of 7.2 then SLAM, and not worry about it until afterwards.

    Maybe this will help?

    - - - Updated - - -

    Ditto to what Tim stated above. I supposed we were answering that the same time.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    Re: Cannot get free chlorine up and combined near zero

    Quote Originally Posted by Texas Splash View Post
    - As for your FC question ... can you please confirm exactly "what" product you added (7 pounds) last night? If it was a type of power, 7lb (112 oz) should shoot FC from 0 to over 60ppm. Am I misinterpreting your note?
    intheswim.com "pool shock" - Pool Shock Chemicals - In The Swim (68% Calcium Hypochlorite). Poolcalculator.com said to add 118oz to get to FC 22:



    - - - Updated - - -

    Quote Originally Posted by Texas Splash View Post
    - As for your FC question ... can you please confirm exactly "what" product you added (7 pounds) last night? If it was a type of power, 7lb (112 oz) should shoot FC from 0 to over 60ppm. Am I misinterpreting your note?
    intheswim.com "pool shock" - http://www.intheswim.com/p/pool-shock (68% Calcium Hypochlorite). Poolcalculator.com said to add 118oz to get to FC 22:

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    Jeremy
    26,000 gallon IG pool, Hayward DE filter, Hayward Ecostar SP3400VSP, Chlorinator, Polaris 9550 cleaner

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    Re: Cannot get free chlorine up and combined near zero

    Jeremy, this may be getting over my head a little, so I'm going to let others try to continue to assist. But I suspect as noted earlier, any potential disparity readings between the test kits and your high CYA levels may be contributing to the frustration. Still, I'm learning myself everyday, so I'm going to watch this thread from a distance and see what other advice you may receive. Best of luck to you!
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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    Re: Cannot get free chlorine up and combined near zero

    Think you might have entered the pool size wrong Splash, I'm getting the same results as keenest for 27,000 gallons.

    So the cal-hypo added CH to your water, which is probably fine although you didn't post a test result for that. High CH can lead to scaling. The pucks you are using are trichlor, which adds 0.6 CYA for every 1 FC. Since FC gets consumed and burnt off by the sun but CYA does not, you can see how it wasn't too hard to get your CYA up to 80.

    As for manual chlorination, it is no more expensive than trichlor. Typically much less expensive, especially when you consider occasional water changes to keep CYA in check. As for labor intensive, pouring a couple quarts in to the pool a night isn't what I call labor intensive, but everyone has different opinions. The favored automated options around here are SWG or stenner pump. The SWG creates chlorine from the salt water. It has a high upfront cost but extremely low ongoing cost if taken care of properly. A stenner pump pumps liquid chlorine from a container in to your pool. It is a good option for people who don't want to mess with saltwater pools for one reason or another, but don't want to mess with chlorine everyday.

    I would say that unless you are going to get an SWG you will want to replace some of your water to lower your CYA before attempting a SLAM. Especially if you plan to continue using pucks you will need to bring your CYA down considerably so you have room for it to rise again. The lower your CYA the easier a SLAM is. A successful SLAM will take care of anything lurking in the water and help you maintain an FC reading going forward.
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
    Pool School - PoolMath - HIGHLY Recommended Test Kits

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    Re: Cannot get free chlorine up and combined near zero

    You're right D! Duhhh My goodness, tough day.

    Sorry Jeremy, your math was correct.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    Re: Cannot get free chlorine up and combined near zero

    Drained and re-filled some water to try to reduce CYA a bit. I read that CYA tends to sit near the top of the water so turning off the bottom drain and dumping to waste a couple of inches from the skimmer should help. Will check CYA tomorrow.

    Applied the liquid chlorine via 8.25% bleach earlier today:


    FC tonight is 9.2
    CC is near to or zero
    Here's to holding steady overnight.

    Thanks everyone. So far this is an improvement over my past "experiments" with other methods.

    - - - Updated - - -

    Drained and re-filled some water to try to reduce CYA a bit. I read that CYA tends to sit near the top of the water so turning off the bottom drain and dumping to waste a couple of inches from the skimmer should help. Will check CYA tomorrow.

    Applied the liquid chlorine via 8.25% bleach earlier today:


    FC tonight is 9.2
    CC is near to or zero
    Here's to holding steady overnight.

    Thanks everyone. So far this is an improvement over my past "experiments" with other methods.
    Attached Images Attached Images
    Jeremy
    26,000 gallon IG pool, Hayward DE filter, Hayward Ecostar SP3400VSP, Chlorinator, Polaris 9550 cleaner

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    Mod Squad tim5055's Avatar
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    Re: Cannot get free chlorine up and combined near zero

    Don't get upset. CYA sitting at the surface is an old wives tale. It is in solution in the bulk water of the pool.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Cannot get free chlorine up and combined near zero

    Quote Originally Posted by tim5055 View Post
    Don't get upset. CYA sitting at the surface is an old wives tale. It is in solution in the bulk water of the pool.

    Well I guess I will be removing quite a bit more water in the future.
    Jeremy
    26,000 gallon IG pool, Hayward DE filter, Hayward Ecostar SP3400VSP, Chlorinator, Polaris 9550 cleaner

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    Re: Cannot get free chlorine up and combined near zero

    Hi Jeremy, I noticed you are using pool calculator.com. That site has stopped being developed, whereas at the top of the page here there is a link to poolmath, which is the newest updated version. Also here at tfp there is Jesse's spreadsheet which incorporates pool math and logs test readings. (Can search for it). Best wishes
    32,000L Fibreglass Leisure Pools IG 12.5'x23'x5' Pump: AstralPools BX1 1.0HP
    Filter: AstralPools ZX-310 SWCG: AstralPools VX7T
    Heater: Hayward H250FDN Test Kit: TF-100

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    Re: Cannot get free chlorine up and combined near zero

    Morning test at 9:30am. This could have been earlier but the results look pretty good except the pH is low. It seems to be fluctuating from ~7 - 7.3

    FC 6.9
    CC .43
    pH 6.9
    CH 219
    CYA - did not read this morning but previously 89 and I swapped some water yesterday.

    Last night's results at 8:30pm:
    FC 8.6
    CC near zero (my device shows lo which indicates it is less than .1)
    pH 7.2

    Am I done SLAMing? Maybe just another SLAM tonight to be sure? I did not turn off my chlorinator last night so it seems there was more than 1ppm of chlorine loss overnight. I would SLAM today but we may want to use the pool later today if the levels are good.

    - - - Updated - - -

    Quote Originally Posted by poolnoob.ca View Post
    Hi Jeremy, I noticed you are using pool calculator.com. That site has stopped being developed, whereas at the top of the page here there is a link to poolmath, which is the newest updated version. Also here at tfp there is Jesse's spreadsheet which incorporates pool math and logs test readings. (Can search for it). Best wishes
    Good to know. Thanks. I have been using poolmath on here instead for the last couple of calculations.
    Jeremy
    26,000 gallon IG pool, Hayward DE filter, Hayward Ecostar SP3400VSP, Chlorinator, Polaris 9550 cleaner

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