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Thread: Lowering CH

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    Lowering CH

    Can anyone tell me approx. how many gallons of water I would need to replace in a 12,000 gal. pool to lower my CH from 460 to 300?
    Thanks. Don
    Don
    12,000g gunite w/ 8'x5' spa, 2 waterfalls, mini pebble,3 Whisperflo pumps, Pentair 4060 DE filter, Intellichor IC20 SWG, MPULSE 3000 Water Treatment System,Sta-Rite gas heater, Kreepy Krauly pool sweep, TF-100 Test Kit.

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    ktdave's Avatar
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    About 35% or 4200 gallons. Roughly 1/3 of your volume. That's assuming your fill water has none. You may want to test that first.
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    Tap water tested at 120. Will this change the amount to be changed?
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    Don
    12,000g gunite w/ 8'x5' spa, 2 waterfalls, mini pebble,3 Whisperflo pumps, Pentair 4060 DE filter, Intellichor IC20 SWG, MPULSE 3000 Water Treatment System,Sta-Rite gas heater, Kreepy Krauly pool sweep, TF-100 Test Kit.

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    Quote Originally Posted by Stinkyfish
    Tap water tested at 120. Will this change the amount to be changed?
    The formula is :

    % to drain = ( PPMNow - PPMTarget) ÷ (PPMNow - PPMSourceWater )

    This translate into (460-300) ÷ (460-120) = 42%

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    Wow that's a lot of water. I better get to draining. Thanks for the info. By the the way, what would cause CH to be so high. I've only just begun to test it w/ my new TF-100 test kit. Pool is 18 months old if that matters.
    Don
    12,000g gunite w/ 8'x5' spa, 2 waterfalls, mini pebble,3 Whisperflo pumps, Pentair 4060 DE filter, Intellichor IC20 SWG, MPULSE 3000 Water Treatment System,Sta-Rite gas heater, Kreepy Krauly pool sweep, TF-100 Test Kit.

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    JasonLion's Avatar
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    Calcium doesn't go away when water evaporates. As water evaporates and you add more water with more calcium in it the total calcium level goes up. Calcium also increases when you use cal-hypo, which contains both chlorine and calcium.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Never used cal-hypo so I guess the lack of rain and lots of sunshine evaporating the water would be the culprit. If I was to install a small water softener on the fill line would that help?
    Don
    12,000g gunite w/ 8'x5' spa, 2 waterfalls, mini pebble,3 Whisperflo pumps, Pentair 4060 DE filter, Intellichor IC20 SWG, MPULSE 3000 Water Treatment System,Sta-Rite gas heater, Kreepy Krauly pool sweep, TF-100 Test Kit.

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    JasonLion's Avatar
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    Water softeners are not designed for the kind of volume of water that pools require. If you only used it for a couple of hundred gallons at a time it would help, but trying even a couple of inches of water at one time will quickly overwhelm the water softener.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    OK, here are the test results after doing a 5000g water change.
    FC: .5
    CC: .5
    TC: 1
    PH: 7.7
    TA: 150
    CH: 410
    CYA: 50
    SALT: 2380
    TEMP: 54 degrees
    I was suprised at the CH reading so I retested the tap water and today it was reading 240. Twice as much as last time I checked.
    In what order should I start adjusting my current readings. I cannot afford anymore water changes as our rates are sky high.
    Thanks
    Don
    Don
    12,000g gunite w/ 8'x5' spa, 2 waterfalls, mini pebble,3 Whisperflo pumps, Pentair 4060 DE filter, Intellichor IC20 SWG, MPULSE 3000 Water Treatment System,Sta-Rite gas heater, Kreepy Krauly pool sweep, TF-100 Test Kit.

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    I wouldn't worry about the Calcium Hardness (CH) level. You can just run with a somewhat lower Total Alkalinity (TA) level to compensate and it will give you an advantage of not having pH rise as rapidly, if that's something your pool has been experiencing. You should also add a little more chlorine, even though the water is cold. Just get it up to around 3 ppm FC and it should stay that way for a while -- probably several weeks before needing to add more unless the pool is exposed to sunlight.

    You can lower your TA (if you want, but not essential right now) by following the procedure in this post where essentially you lower the pH and aerate, adding acid to keep the pH low. However, at the colder water temperature, this procedure might not be very efficient so you could just add some acid to drop the pH to 7.5 (and do that periodically if the pH rises) and wait until spring to lower the TA then.

    Your water is not terribly over-saturated at this point, especially at the lower temperature, so you could just leave things alone until spring. I think that's the easiest thing to do right now.

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Thank you Richard, you just made my day. I thought this CH thing was going to be a big deal.
    Don
    12,000g gunite w/ 8'x5' spa, 2 waterfalls, mini pebble,3 Whisperflo pumps, Pentair 4060 DE filter, Intellichor IC20 SWG, MPULSE 3000 Water Treatment System,Sta-Rite gas heater, Kreepy Krauly pool sweep, TF-100 Test Kit.

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