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Thread: High CH, what to do??

  1. #1
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    High CH, what to do??

    I just tested my CH and it came out to 640, but it should be somewhere around 300.

    Is there any way to lower it other than adding more water? And what will happen if I just leave things as they are until evaporation causes enough water loss and replacement to bring it into the right range? According to the pool calculator I'd have to replace 53% of my water or over 15,000 gallons!!!!

    I had a major calicum scale problem when the pool was opened this year, but after two no-drain acid washes, the walls and floors are smooth again, but I'm still kicking up white "dust" when I brush. (Don't know if that's related or not, but it is another data point)

    Here are the total test numbers:

    FC 1
    CC 1
    TC 2
    pH 8.2 (currently much lower)
    T/A 180
    CH 640
    CYA 54 (I know I have to bring this up)

    Do I need to do anything drastic about my high CH or can I ride it out?

    Thanks!
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

  2. #2
    Mod Squad jblizzle's Avatar
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    Re: High CH, what to do??

    Evaporation does not lower CH ... it actually makes it higher since the calcium stays in the pool when the water evaporates.

    The only 2 methods to lower CH are:
    1. Replace water with a lower CH water source (tap or rain water)
    2. Hire someone to do a Revers Osmosis treatment on your pool water ... which actually also requires some water replacement.

    If you are diligent about your keeping your pH levels low (which based on the numbers above may be questionable), you can live with the high CH. Some members here are over 1000ppm.
    Jason, TFP Moderator
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  3. #3
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    Re: High CH, what to do??

    You could do a reverse osmosis treatment to lower your CH. But that cc=1 leads me to think you may be kicking up algae. With a cya of 50 your fc should not get below 4, so you may be fighting an algae bloom.
    17,000 gal, IG Gunite Diamond Brite plaster Kidneybean,w/7x11 tanning ledge& 3x5 swimout bench,244T 300lb Hayward Pro high rate sand filter(63 GPM) , Hayward 1Hp Super Pump w/3/4 hp booster pump, Polaris 280, Laars Lite 2 175k N/G Heater, Tf-100, Speed stir

  4. #4
    Mod Squad jblizzle's Avatar
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    Re: High CH, what to do??

    Yeah, like Rob said ...

    Based on your test results I should have said that #1 priority to to lower the pH into the low 7s and based on the CC > 0.5 and the low FC level for your CYA level, you really should start with the Shocking Your Pool process now or right after you do a water change if that is what you decide to do.
    Jason, TFP Moderator
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  5. #5
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    Re: High CH, what to do??

    Thanks folks!

    A note about the high pH......I'm only at the pool on the weekends and this is only the second year of it being opened, so every week I find a very high pH which I bring back to the low 7's, but by the following week it is back up again. I thought that by now the plaster would have stabilized (probably the wrong word) and my pH would have remained constant, but it is still creeping up week after week.

    Assuming I take care of the low chlorine numbers (already turned the SWG up to 45%) and the high pH (weekly doses of muriatic acid to bring it down) and raise the CYA (I added all the CYA I had left and will resupply this week), what does the high CH mean?

    Can I just leave things like they are and wait it out, or will that create big problems down the road?

    Thanks again.
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

  6. #6
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    Re: High CH, what to do??

    Lower your TA. That's part of why it's swinging wildly.
    pool-school/lowering%20total%20alkalinity
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II T100 Sand Filter, CompuPool CPCS48 SWG, TF-100 test kit

  7. #7
    Mod Squad woodyp's Avatar
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    Re: High CH, what to do??

    Just running the SWG has a tendency to raise pH all by itself.
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  8. #8
    Mod Squad jblizzle's Avatar
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    Re: High CH, what to do??

    If you pH keeps rising with the high CH values you put yourself at risk of continual scaling.

    Note that the SWG and high TA are probably the largest contributors to the rising pH

    If you spent some time Lowering Total Alkalinity, you may be able to reduce how fast the pH rises.

    But, there is no point in adjusting things before you decide if you are going to change water. If you have made the decision not to change water, then you should follow the Shocking Your Pool process (usually with the SWG OFF) to make sure everything is dead. And then start to work on your TA.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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  9. #9
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    Re: High CH, what to do??

    Be sure you test your fill water before you decide that draining and refilling is the solution. It wouldn't be good if you went to all that trouble and expense to find out your fill water has high CH.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II T100 Sand Filter, CompuPool CPCS48 SWG, TF-100 test kit

  10. #10
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    Re: High CH, what to do??

    Thanks again folks!

    My inclination would be to not drain the pool and refill, so I'll try to bring the rest of the numbers in line ASAP.
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

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