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Thread: Calcium Hardness & Phosphates Way Too High

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    Calcium Hardness & Phosphates Way Too High

    My plaster pool was completely resurfaced and refilled 3 summers ago (2011). In that time I switched to the BBB method and while this worked and looked good for 2 summers, it's falling apart now.

    My CH level has consistently gone up and nothing brings it down... not even overflows of rain water. And I have been told that with my numbers, I will not be able to prevent damage to the surface or the equipment OR have the chemicals I'm adding make any difference. I have been getting regular algae blooms this summer and cannot make them go away. My pool is also not holding an FC level, no mater how much bleach I add or how many times I SLAM it. The pool store says the phosphates are responsible for the algae.

    Current numbers are as follows:

    FC = 0
    CC = 0
    PH = 7.4
    TA = 110
    CH = 500-610
    Phosphates = 2500
    CYA = 50-60
    Borates = 60

    I have a TAS-DPD kit and regularly test my chemicals, though I also take my water to the store for testing (since I can't test phosphates at home).

    Do I really have to drain and refill again after only 3 summers?

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    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Calcium Hardness & Phosphates Way Too High

    Phosphates are meaningless if you maintain adequate FC. You must not be following the SLAM process correctly to eliminate it and then are letting FC drop too low.

    That CH is not terribly high, you just need to maintain pH in the lower 7s. But you are getting close to being to replace water.
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    bridgman's Avatar
    Join Date
    Mar 2014
    Bowmanville, ON Canada

    Re: Calcium Hardness & Phosphates Way Too High

    OK, so dumb question here -- a SLAM continues until 3 conditions are met, one of those is passing an Overnight Chlorine Loss Test... so if you've finished the SLAM then you aren't losing chlorine at night.

    General recommendation here will be to ignore the phosphates, since as long as you maintain an appropriate FC level for your CYA level then you won't get algae growth no matter what the phosphate levels. Usually when a pool won't hold FC that means you let the FC level get too low at some point (for CYA of 50-60 that means FC below 4-5) and algae started growing.

    If you raise FC to normal target level (8-9) for your pool what does it read when you test the next day ?
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    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Calcium Hardness & Phosphates Way Too High

    How many times? The SLAM is a one-time thing that might last a couple weeks. It is the acronym for Shock Level And Maintain. The chlorine consumption will go back to normal once you kill all the algae, and that includes any lurking inside and behind ladders, stairs, and lights.

    Why such a spread on CH? 500-610? Actually, neither one is unmanageable. You just need to maintain pH at the low end of the comfort zone and drop TA enough to keep the CSI close to zero. Poolmath will tell you the CSI. I'm not growing scale and my CH is usually above 800. Play with it; plug your numbers in the now column and look at the CSI. Then raise and lower the targets one at a time and see how it affects things.

    And after three seasons, you're still listening to the pool store hacks' phosphates scare tactics?
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    Re: Calcium Hardness & Phosphates Way Too High

    I think that we're going to need a lot more information before we can get you back on track. Algae is caused by insufficient chlorine levels for your cyanuric acid level. The fc will hold once the Slam is complete and you make sure that the fc never ever goes below 7.5 % of your cyanuric acid level. I would recommend maintaining fc at 15 % of the cya for a week after the Slam and then a minimum of 10% for at least two weeks. The methods work when applied correctly and consistently.

    How did your calcium level get so high?

    What is the calcium level of the fill water?

    What do you use for chlorine?

    With a zero chlorine, you're going to have problems. You have to add as much chlorine as it takes to maintain the minimum level. If the chlorine you're using does not have the expected result, then it might be bad.

    Also, forget about phosphates.

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    Re: Calcium Hardness & Phosphates Way Too High

    Thanks for the help. I'll try to respond to everything...

    1. I will be ignoring Phosphates. Luckily, I haven't bought anything to tackle them, but with my algae not going away, I started thinking phosphates were the only thing left.

    2. When slamming, I've been bringing the pool to between 16-20 ppm of FC (I use 8.25% bleach), waiting an hour, then bringing it to slam level again. But I can only do this about 3-4 times/day. The next day the FC is 0. I don't know how to get ahead of the algae or whatever's consuming the FC.

    3. The spread on my CH is the difference between the pool store test (500) and mine (610). I don't know how the levels got this high and no one can tell me.

    4. I don't know the CH of my tap water, but I will test it with my home kit.

  7. Back To Top    #7

    Join Date
    May 2014
    Current: Singapore Previous: Clayton, Victoria, Australia

    Re: Calcium Hardness & Phosphates Way Too High

    SLAM targets have recently been updated to 0.4*CYA, seems like you might be using the old SLAM targets.
    If FC drops to 0 the next day, it is indicative of algae/organics. The way to get ahead is to continue dosing the pool with bleach.

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    JasonLion's Avatar
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    May 2007
    Silver Spring, MD

    Re: Calcium Hardness & Phosphates Way Too High

    While the algae will get killed more quickly if you can raise to SLAM level more frequently, doing so 3-4 times a day is sufficient. The whole process can easily take a week. Continue raising to shock level and be patient.

    The most common source of high CH is tap water. You didn't say where you live, so I can't be sure. But in many areas of the country tap water CH is 100+. Over time a tap water CH level of 100 can get concentrated in the pool by evaporation to far higher levels. Test your fill water CH level to see if this is an issue for you.
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