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Thread: Can't maintain chlorine level

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    RdRunner's Avatar
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    Can't maintain chlorine level

    Since the end of May, we have been unable to maintain a chlorine reading in our pool. Been getting the water tested at the pool store. Everything checks out ok, except chlorine is below 1. They tested for phosphates and said ours was "off the charts", so we have been putting in phosfree to deal with that problem. Finally got the phosphate reading below 100 and shocked with granular chlorine, but even one hour later, no showing of chlorine on the test strip. I took a sample to the store the next day and chlorine is below 1.

    Readings from pool store Saturday:

    C - less than 1 (don't know FC & CC)
    Ph - 7.4
    TA - 100
    CH - 300
    CYA - 60

    Using Trichlor tabs in an automatic chlorinator

    Found this site and used bleach last night. One hour after adding the bleach, the chlorine reading was in the shock range. This morning, no sign of chlorine.

    Any ideas what is wrong?
    25000 gal., IG, vinyl liner, Sand filter, 1 HP Hayward pump

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    Mod Squad Bama Rambler's Avatar
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    Re: Can't maintain chlorine level

    Sounds like you have an algae bloom to me.

    At least you've started on the right road now. Keep in mind that pool store tests are notoriously inaccurate.

    1) Read Pool School (link in my sig)
    2) Read it again!
    3) Purchase a good test kit.
    4) Did I mention that you need a good test kit?
    5) You did good by using bleach, but remember Shock is a process not a product! Keep adding bleach as often as it takes to keep your FC level at shock level for your CYA level. (Which is 24 ppm according to your CYA).
    6) Stop adding anything but what's recommended here to your pool.

    Follow the advice you get here and you'll have a sparkly, trouble free pool in no time.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    frustratedpoolmom's Avatar
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    Re: Can't maintain chlorine level

    Hi and welcome.

    Phosphates are algae food, but in a properly chlorinated pool they are irrelevant. It's also not necessary to treat them when trying to get chlorine to hold. So in the future, you don't need phosfree or similar chems. Those products are pure money makers for the pool stealers.

    So read Pool School, get a good test kit.

    Read How to Shock your Pool. What you need to understand is you have organics that you can't see, because they are consuming the chlorine as you add it. If you were to stop chlorinating, the pool would go green in a day, 2, tops. Right now, you are just keeping the algae from becoming a full-on bloom.

    You need to reach shock level, and hold it there, with frequent, hourly if possible, bleach additions....holding it at shock level until the FC holds overnight (that's why we recommend a good test kit). Once the shocking kills the nascent algae, your FC will hold.

    No more trichlor pucks, stick with bleach. Refer to the CYA chart for your appropriate levels, now that your CYA is 60. Once you are done shocking, never let the FC drop below the "min" and algae won't be a problem.

    Hope this helps, if you need clarification on anything just holler!
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Re: Can't maintain chlorine level

    Quote Originally Posted by RdRunner
    ...and shocked with granular chlorine, but even one hour later, no showing of chlorine on the test strip. I took a sample to the store the next day and chlorine is below 1.

    Found this site and used bleach last night. One hour after adding the bleach, the chlorine reading was in the shock range. This morning, no sign of chlorine.

    Any ideas what is wrong?
    There are organics in the pool that are consuming the bleach, it happens very rapidly. You will need to test the pool every few hours and add MORE bleach until you can maintain that shock level overnight with negligible loss.

    Have you cleaned out the skimmers, the bottom of the pool, the bag on the pool cleaner if there is one? First, get the visible stuff out of there, they suck up chlorine. Then, does the filter need cleaning? Take a look, however it is that you check that on your filter.

    After all that is cleaned out, take a look around the pool. Any algae that you can see, behind ladders, on steps, on edging, waterfall? Scrub that. Then retest since as you wear off the protective covering on top of the algae, the chlorine attacks it and gets consumed.

    How is the water looking? Brush the walls and floor really well... did that kick up any cloudiness or dusty grey or green? You are using up chlorine (and killing algae), test again.

    Probably, you have a little algae everywhere that you just are not seeing. Hitting it once with bleach is like taking one swat at a swarm of bugs... so you kill 2 but leave 50, they will be back for sure!

    You need to follow the directions the pros here will patiently give you.... get a proper test kit to find out what shock level you need based on CYA, get to that level and keep it above that level until you are done. That is, holding chlorine overnight, CC's at 0.5 or less, and sparkly clear water.

    (A neighbor came over recently and upon seeing the pool she exclaimed, "Your pool is so BLUE!" -- Funny, she used to swim in this pool when the prior owner had it but it had never been so blue? Makes me wonder what color it was!)
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    RdRunner's Avatar
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    Re: Can't maintain chlorine level

    Ok, we have added 4 more gallons of bleach. I am on my way to get a test kit now. Town is 50 miles away. This seems like an awful lot of bleach to be pouring in here, are you guys sure about this? I will have accurate test results this evening, if the store has the kit.

    I notice from the signatures, that a lot of people on this forum still use the automatic chlorinator. Are the tabs really of no use?
    25000 gal., IG, vinyl liner, Sand filter, 1 HP Hayward pump

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    Re: Can't maintain chlorine level

    where are you seeing that? not many people use them except for vacations or something along those lines. you can use them to raise the cya a bit. you can also use them to kill spots of black algae or fade organic stains. but overall they're evil imo. you haven't even started adding bleach compared to what some people have to add. what kit are you going for? the recommended ones generally aren't found in stores unless you're wanting the one from walmart to old you over.
    16x32 21,000 gallon in-ground exposed aggregate, 1.5hp pump, 120 sqft catridge filter, birdcage, solar panels, aquavac tigershark qc robot.

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    Re: Can't maintain chlorine level

    Quote Originally Posted by RdRunner
    Ok, we have added 4 more gallons of bleach. I am on my way to get a test kit now. Town is 50 miles away. This seems like an awful lot of bleach to be pouring in here, are you guys sure about this? I will have accurate test results this evening, if the store has the kit.

    I notice from the signatures, that a lot of people on this forum still use the automatic chlorinator. Are the tabs really of no use?
    I just put 1.4 gallons of 6% bleach in my pool to get it from 3 ppm to 7 ppm. My pool is sparkly clean and beautiful, but with some rough rocks in the waterfall and the edging that tend to grow algae no matter what. So, I add that much bleach about every 4th or 5th day.

    I do have an automatic chlorinator which I am using a little right now to bump up the CYA (by about 10) and to keep a little extra chlorine in use since it is so dad-gummed hot right now with no rain in sight. (thunder daily but not more than a moment of sprinkles). After 7 or 10 pucks I will stop that but for vacations. Right now that is giving me that final day between bleach additions I think. Then I will go back to additions every 3rd or 4th day (depends on weather and usage).
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    RdRunner's Avatar
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    Re: Can't maintain chlorine level

    Ok, I got the test kit from Leslie pool store. It is a DPD test kit with Taylor regents. I vacuumed the pool, backwashed the filter, and tested the water.

    FC - 5 ( 4 gallons of bleach were added at about 11 am)
    TC - 5
    CC - 0 (if I did the math right)
    PH - 7.2
    TA - 95
    CH - 420
    CYA - 50

    Should I add some bleach to get the chlorine up for the night?
    The water looks just a little cloudy, not bad. I can see the drain in the deep end (8"), but the water doesn't sparkle like it is supposed to.
    25000 gal., IG, vinyl liner, Sand filter, 1 HP Hayward pump

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    Re: Can't maintain chlorine level

    Quote Originally Posted by reebok
    what kit are you going for? the recommended ones generally aren't found in stores unless you're wanting the one from walmart to old you over.
    you got the wrong one. this will be a bigger pain than it would be if you had gotten the correct one, or the one from www.tftestkits.net, but like I said, you probably won't find the right one at a local store. you need to keep your free chlorine level at shock level for your pool as often as possible, as often as every hour if you can. at least twice a day. your shock level is 20 which can be found here: pool-school/chlorine_cya_chart_shock
    your kit can test up to 10ppm free chlorine if you have distilled water to use and dilute the test, which loses accuracy, and of course 10 is half of what you need to be keeping it at. so you can try to do it anyway with that kit, it will just be more difficult, or you can supplement your kit by buying the fas-dpd test (by itself) from www.tftestkits.net or directly from taylor.
    16x32 21,000 gallon in-ground exposed aggregate, 1.5hp pump, 120 sqft catridge filter, birdcage, solar panels, aquavac tigershark qc robot.

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    RdRunner's Avatar
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    Re: Can't maintain chlorine level

    Hey Reebok,
    Thanks for your reply. I had already found the correct shock level at the link you listed and I have added the necessary bleach according to the pool calculator. I got the best kit available at Leslie's pool store, I know that was better than waiting for one that I had to order online. If it isn't perfect, I can upgrade later.
    Thanks to everyone for helping out. It will be interesting to see how much chlorine is in there tomorrow morning.
    25000 gal., IG, vinyl liner, Sand filter, 1 HP Hayward pump

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    frustratedpoolmom's Avatar
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    Re: Can't maintain chlorine level

    Your kit is just missing the FAS-DPD test. You need it because your shock level is 20 and your kit only reads up to 5. You can order the test to supplement your kit, it will be cheaper than replacing the whole thing.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Re: Can't maintain chlorine level

    Thanks frustratedpoolmom for that info. I will try to get that addition to my kit. The one I have gives instructions on diluting the sample and then multiplying results to read levels higher than 5. I suppose that is not too accurate, but it will have to do for now.

    I got the level to 20 (best I can tell) last night and it looks like around 15 this morning. I had vacuumed all the dead stuff out last night and there doesn't seem to be much of anything on the bottom this morning. I think that is a good sign that maybe we have killed most of it, right?

    We will keep close check on it throughout today and maintain shock level. When should we be able to let it drop back down to normal levels?
    25000 gal., IG, vinyl liner, Sand filter, 1 HP Hayward pump

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    frustratedpoolmom's Avatar
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    Re: Can't maintain chlorine level

    When the FC holds overnight and you don't lose more than 1ppm during the dark, then you can let it drop. The dilution method does lose some accuracy, so keep that in mind.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    RdRunner's Avatar
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    Re: Can't maintain chlorine level

    I am ready to close out this chapter. Thanks to everyone who gave instructions. The pool looks great now, chlorine has held steady for 2 days. I have added some water now since I had been backwashing frequently and the level was getting low. That brought the chlorine level down some, and I haven't added bleach for 2 days now. Level is around 12.

    I am now a faithful follower of the posts here and hope to become proficient with the BBB method for maintaining my pool.

    Thanks again.
    25000 gal., IG, vinyl liner, Sand filter, 1 HP Hayward pump

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    RdRunner's Avatar
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    Gettin started with BBB

    Topics Merged by Moderator

    We have now cleared up the problem we had last week when we found this site. Now have recent test results.
    FC - 12 (coming down from shock level of 20 over past few days)
    TC - 10
    CC - 0 (these numbers are best guess from dilution method, dont currently have FAS/DPD kit)
    PH - 7.4
    TA - 90
    CH - 400
    CYA - 40

    The water looks great. Pool calculator says to add 22 oz borax to raise PH. The only suggestion for the high CH is to drain 25% of pool water and refill. Is it bad enough that I need to do that?
    25000 gal., IG, vinyl liner, Sand filter, 1 HP Hayward pump

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    Re: Gettin started with BBB

    Leave your pH alone. 7.4 is fine.

    Drain is the only solution to high CH but yours is at the upper limit of acceptable and I would not attempt to reduce it. You might test your fill water to see where it is. If it's low in CH, then that coupled with rainwater will take the CH down to an acceptable level over time.

    Were you using Cal Hypo to chlorinate?

    I would suggest leaving your posts in one thread so folks can see the "history" of your story and give much better advice.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    frustratedpoolmom's Avatar
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    Re: Can't maintain chlorine level

    I agree with Dave, your PH is fine. As long as it stays below 7.8 your CH isn't a problem, but I'd avoid Cal-hypo.

    FC + CC = TC, so something is off in your numbers, since TC can't be lower than FC - typo - I hope?
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    RdRunner's Avatar
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    Re: Can't maintain chlorine level

    That TC total was a typo, both are 12.
    25000 gal., IG, vinyl liner, Sand filter, 1 HP Hayward pump

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