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Thread: Calcium Hardness?

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    jwp's Avatar
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    Calcium Hardness?

    Hello All,

    I'm curious as to what drives my CH number down. Will high chlorine take the number down?

    Thanks.
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    Re: Calcium Hardness?

    Once CH gets in the water, it stays there. So if yours is lowering, you're probably losing water somewhere. If you get a lot of rain, that will do it -- rainwater has zero CH. Wait - it's indoor, so that won't apply. Or your kids do a lot of cannonballs and you're constantly refilling with soft water. Or you have an autofiller than won't shut off and you're constantly diluting it.

    The very worst option is that the Calcium is still there, just no longer in the water but sticking to the pool walls in the form of scale.
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    Re: Calcium Hardness?

    Richard320, thanks for the quick reply.

    Well, we have a lot of swimming activity and we do add water from a water softener system. So, I'm hoping that is it.

    If it were sticking to the walls, is it possible to know? Is there something you can do to see if that is happening?

    Water Test results:

    FC = 7.0 (just added Chlorine yesterday)
    CC = 1.0
    PH = 7.5
    TA = 110 (in process of lowering by taking PH to 7.2 and letting it rise, repeat)
    CH = 250 (was 300 2 days ago)
    CYA = 30
    Salt = 3000


    Thanks.
    14K gallons...Inground, Indoor, Plaster...SWGPool Pilot Digital Nano
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    Re: Calcium Hardness?

    You'd see patches of greyish tan scale growing in areas with poor circulation. Just sort of blotchy. When it gets extreme, it's like growing sandpaper on the walls, and swimmers would get road rash from brushing against it. Your pH is low enough that I don't see it happening, although if you let it rise too high in the past, it's still a possibility.

    Test your fill water. If it's close to zero CH, it can cause what you describe. Figure out your average depth. Odds are, it's somewhere between 4 and 5 feet, unless the pool is all shallow. If the pool is 50" (for easy math) and you lose 2" a day, that's a 4% reduction of CH (and salt and CYA) every day.

    From 300 to 250 isn't too big a drop, really. The CH test is only accurate plus or minus a drop, so your loss could be lower than you think.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Calcium Hardness?

    Richard320...again, thank you

    Our fill water has a CH of 0. We add approximately 4" of fill water per week. Sometimes more when we have a lot of kids swimming.

    I don't see any grayish-tan sandpaper spots on the walls anywhere. However, I do see some areas where pitting may have occurred with previous owners.

    Thank you for the advice, knowledge and quick help.
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    Re: Calcium Hardness?

    Okay, so my next question...

    I went through a SLAM a week ago and it took three days to past the OCLT. The water looked spectacular.

    Now, a week later the water is starting to cloud again. Admittedly, the chlorine got below Minimum FC, but now it's back right and even looking better. (I turned the SWG on late)

    So, could I have mustard algae? What is the typical reason for cloudiness returning?

    Im thinking about SLAMMING again and then finishing with a 24 hour Mustard Shock.

    Any advice?
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    Re: Calcium Hardness?

    Water cloudiness tend to be indicative of bleached algae carcasses.
    Allowing chlorine to drop below minimum would have allowed algae to take root.
    Definitely SLAM, but nothing you have stated so far points to mustard algae.

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    Re: Calcium Hardness?

    Okay, thanks.

    I was wondering because I read the mustard algae article and it said it clears up with a SLAM and then clouds up again, which is what happened to me.

    I will do a SLAM again.
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    Re: Calcium Hardness?

    Quote Originally Posted by jwp View Post
    I was wondering because I read the mustard algae article and it said it clears up with a SLAM and then clouds up again, which is what happened to me.
    I don't see where it says that in the Mustard Algae Pool School article.
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    Re: Calcium Hardness?

    Here is a quote from the article...

    "Mustard algae is a particularly persistent kind of algae, that appears to go away when you SLAM the pool normally, only to reappear as soon as you come back down to normal chlorine levels."

    It's the first sentence of the article. I'm not saying that I have Mustard Algae, but that is sort of what we experienced.
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    Re: Calcium Hardness?

    Now I understand. The "clouds up again" confused me. Yes, yellow/mustard algae can come back at normal chlorine levels if you don't completely eradicate it. It takes roughly twice the active chlorine level to keep yellow/mustard algae from growing -- about a 15% FC/CYA ratio. Since that can be impractical to maintain since it's double the daily chlorine usage (loss from sunlight, etc.), the goal is to completely eradicate the algae from behind light niches, under removable ladders, and other shady areas where it prefers to grow.
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    Re: Calcium Hardness?

    Is there a good way to tell if I have it?

    Are you saying I should pull out the pool light when we run the Mustard Shock levels?

    Thanks for your help, chemgeek
    14K gallons...Inground, Indoor, Plaster...SWGPool Pilot Digital Nano
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    Re: Calcium Hardness?

    If you have algae that looks yellow or mustard in color, generally grows only on the shady side of the pool, and poofs up when you brush it, then it's more likely to be yellow/mustard algae. If the water is just cloudy and you haven't caused that by brushing, it's more likely to be green algae or some other non-algae source of cloudiness. If the cloudiness comes back even though your FC/CYA ratio is 5% or more for an SWG pool (i.e. the minimum in the Chlorine / CYA Chart in the Pool School), then you have something else wrong perhaps with circulation in that area of the pool or test error or something new we've never seen before. Given what you wrote here:

    Admittedly, the chlorine got below Minimum FC, but now it's back right and even looking better.
    I think you are just getting green algae to grow if you go below the minimum FC. Green algae sometimes makes the water look dull/cloudy rather than being a visible green algae bloom. Unless the algae is clumped, it doesn't look green. So in its early stages of growth if it's dispersed it just diffracts the light to make the water look cloudy. Basically, the algae is able to grow faster than chlorine can kill it because you were below the minimum needed to prevent that from happening.
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    Re: Calcium Hardness?

    chem geek, thank you very much. Based on what you're saying and what I see I think it's just green algae. I've been running a SLAM for 24 hours and the water is crystal clear...and I've not lost more than 0.5 FC and the CC has not been over 0.5.

    Ill do a better job at maintaining the FC this time and see what happens. Again, thank you.
    14K gallons...Inground, Indoor, Plaster...SWGPool Pilot Digital Nano
    Hayward 1.5HP pump/Hayward Star Clear Plus - Cartridge
    Sta-Rite Max-E-Therm Heater 400K BTU LP
    Hot tub (600 gallons) flowing into pool

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