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Thread: crystal crete dissolving

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    crystal crete dissolving

    The pool where I work is about 14 years old. I try my best to keep the water chemistry in line. Our current problem is that the crystal crete is disssolving and coating the filter grids. The boss has agreed to get it resurfaced for the first time this fall. Anything I can do to prevent it from dissolving further?

    My PH tends to lower itself, but is currently about 6.8

    Alkalinity is 100

    CH was very high, so am guessing it is from the dissolving crystal crete

    Chlorine is kept in the normal parameters, but sometimes drops when I have a day off.

    Thanks for your help!!!
    46,000 gallon in ground concrete/crystal crete, filter is Pentair Pack Fab 60 DE, freshwater.
    2hp pump. Flow Rate ? 4 return jets, two of which are closed due to a leak in the plumbing
    Water is replaced/replentished using RO water

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    Mod Squad Bama Rambler's Avatar
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    Re: crystal crete dissolving

    A full set of test results from a good test kit would tell us a lot more. Keeping everything balanced to the recommendations here is the best thing you can do.
    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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    Re: crystal crete dissolving

    Thanks, don't have time at the moment to do a full test, but I can tell you this:

    FC is kept in the normal range
    CC haven't ever tested
    PH is low and tends to drift down, add soda ash regularly
    TA is 100
    CH is very high, quit the test when it hit over 400
    CYA also very high, WAY off the charts last time I tested.

    Thanks!
    46,000 gallon in ground concrete/crystal crete, filter is Pentair Pack Fab 60 DE, freshwater.
    2hp pump. Flow Rate ? 4 return jets, two of which are closed due to a leak in the plumbing
    Water is replaced/replentished using RO water

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    duraleigh's Avatar
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    Re: crystal crete dissolving

    Your chemistry is almost surely your problem but if you don't test, you will not control it.

    pH should be in the 7's at all times never below or above
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    linen's Avatar
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    Re: crystal crete dissolving

    Also, I am guessing you are using trichlor pucks (or dichlor granules) to chlorinate...that would cause your ph to continually go down and your cya to get too high (both of which cause significant problems). Both of these need to be addressed to help your situation.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: crystal crete dissolving

    Yes, am using tri-chlor pucks and I'm sure they're the reason the ph is always creeping down. I try to offset it using cal hypo, but am all out at the moment. I've burned through all of my soda ash as well trying to keep up the ph, about 200lbs since October.

    I've told the boss about the cya and the fact that we need to drain the pool to fix it, but she won't listen. As long as the water is clear and we pass our govt. health inspection, she thinks all is well. What sort of problems can a high cya cause? I've asked around a bit, but have only gotten vague answers.

    Thanks again!
    46,000 gallon in ground concrete/crystal crete, filter is Pentair Pack Fab 60 DE, freshwater.
    2hp pump. Flow Rate ? 4 return jets, two of which are closed due to a leak in the plumbing
    Water is replaced/replentished using RO water

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    Patrick_B's Avatar
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    Re: crystal crete dissolving

    Cya buffers Chlorine which is good, but too mush of creates problems if you need to SLAM (shock) the pool as it will require more FC to do the same job.

    That said, Cya is not the cause of your finish problems. It is mostly because of continual low pH in my opinion.
    TFP Moderator
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    ABC's Of Pool Chemistry, Test Kits, SLAM Your Pool
    28K Gal IG FreeForm, CLI Quartz, Pentair 36"SF & VS Pump, Dolphin M5, Rheem

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    Re: crystal crete dissolving

    I've got an order of chemicals on the way. I plan to keep the PH in check by using more cal hypo and of course soda ash. That leaves me with a high CYA to deal with. Will a high CYA cause my chlorine test results to be low? I know I have to use more chlorine to get the same effect, but will it alter the test results? Seems like every year I'm going through more and more chlorine...
    46,000 gallon in ground concrete/crystal crete, filter is Pentair Pack Fab 60 DE, freshwater.
    2hp pump. Flow Rate ? 4 return jets, two of which are closed due to a leak in the plumbing
    Water is replaced/replentished using RO water

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    Re: High CYA

    Posts merged, Please keep your questions in your own topic. Bama

    I've asked about this in another thread, but this is a more appropriate place. My Cya is so high it can't even be measured. My boss won't let me drain the pool though.

    My question is, does a high Cya affect my chlorine test results? I know that I need to add more chlorine to get the necessary sanitation, but will all of that Cya bond with my chlorine and not allow it to show up in the tests? It seems like every year I go through more and more chlorine.

    Thanks for all of your help!
    46,000 gallon in ground concrete/crystal crete, filter is Pentair Pack Fab 60 DE, freshwater.
    2hp pump. Flow Rate ? 4 return jets, two of which are closed due to a leak in the plumbing
    Water is replaced/replentished using RO water

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    Mod Squad Bama Rambler's Avatar
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    Re: High CYA

    It doesn't affect the test. I does, as you know, affect the amount of FC required.

    With very high CYA you probably have a nascent algae bloom and can't get rid of it. That's probably what's causing your high chlorine consumption.
    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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    Patrick_B's Avatar
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    Re: crystal crete dissolving

    +1 to what Bama says..

    It makes sense. Your Cya being high requires more Chlorine to do the same job, especially when you are killing Algae.
    TFP Moderator
    Essential Links:
    ABC's Of Pool Chemistry, Test Kits, SLAM Your Pool
    28K Gal IG FreeForm, CLI Quartz, Pentair 36"SF & VS Pump, Dolphin M5, Rheem

  12. Back To Top    #12

    Re: crystal crete dissolving

    200 lbs of soda ash since October? That's quite a lot.

    Your TA is probably mostly, or all, cyanuric acid. This will make your CSI very low. Until you get accurate measures of all of your chemistry, and get them balanced, you will continue to have problems.

    What is getting caught in the filter, aggregate?

    Does the heath department regulate cyanuric acid levels?

    How much trichlor have you used since October?

    It is my opinion that the pool should be closed until the chemistry is correct. As a professional pool operator, it is your duty to ensure the safety of your guests.

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