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Thread: Adjusting pH and CH?

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    AClogston's Avatar
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    Adjusting pH and CH?

    I know you shouldn't adjust your CH and Alkalinity (with sodium bicarbonate) within 24 hours of each other, or so I've read. Is the same applicable to using soda ash to adjust pH and raising calcium?

    I adjusted the pH this morning using sodium carbonate, but would like to raise the CH after the pool closes tonight, so I don't have to do it before opening tomorrow (thus limiting downtime). Should I still wait 24 hours?
    -Alex
    Outdoor Chlorine Pool/Spa (~100' from pump room):(35,000gal IG, plaster, 2 Triton TR-140 sand filters, 2 2HP pumps),(1,200gal IG, plaster, Triton TR-140, 2.5HP pump [circ.], 2 2HP pumps [jets])
    Indoor Bromine Pool/Spa:(24,000gal, plaster, Triton TR-100, 1.5HP SVRS-equipped pump),(3,200gal w/ 3 waterfalls, plaster, Sta-Rite System 3 cartridge filter, 3HP pump [circ.], 3HP pump [jets])

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    Re: Adjusting pH and CH?

    I know you shouldn't adjust your CH and Alkalinity (with sodium bicarbonate) within 24 hours of each other, or so I've read.
    Hmmm, I can't figure out why. I certainly have done so and would do so again. What was the reasoning behind that?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Adjusting pH and CH?

    Locally high calcium and carbonate levels can create a calcium carbonate precipitation reaction. I like to allow at least 8 hours between adding pH or alkalinity increaser and calcium chloride. Besides just allowing the chemicals to circulate and mix, they also need to reach a new equilibrium with everything else. Perhaps 8 hours is not necessary, but I would rather be conservative and wait.

    Adding pH increaser clouds the water. I like to wait until the water is very clear again before adding calcium chloride after adding pH increaser.

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    AClogston's Avatar
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    Re: Adjusting pH and CH?

    Copied from: http://www.thepoolprofessor.com/hints.html (which is definitely not the source I got it from.)

    "It is recommended that you do not adjust the water’s alkalinity and hardness within 24 hours of each other. If sodium bicarbonate is used to adjust the total alkalinity you should wait at least 24 hours before adding calcium chloride for increasing water hardness."

    It isn't in the CPO book so maybe it was in the Taylor pool chemistry book. I don't remember exactly what it said, but something about the calcium chloride and sodium bicarbonate combining to create an insoluble that clouded up water.

    If it was just snake oil, I bought some, lol. Is it perfectly fine to adjust these levels more closely together? If so what kind of window are we talking? An hour between the two adjustments? Eight hours?
    -Alex
    Outdoor Chlorine Pool/Spa (~100' from pump room):(35,000gal IG, plaster, 2 Triton TR-140 sand filters, 2 2HP pumps),(1,200gal IG, plaster, Triton TR-140, 2.5HP pump [circ.], 2 2HP pumps [jets])
    Indoor Bromine Pool/Spa:(24,000gal, plaster, Triton TR-100, 1.5HP SVRS-equipped pump),(3,200gal w/ 3 waterfalls, plaster, Sta-Rite System 3 cartridge filter, 3HP pump [circ.], 3HP pump [jets])

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    Re: Adjusting pH and CH?

    It's chemistry that is above my pay grade but I have put them in my pool within an hour of each other with absolutely no observed unwanted reaction.

    If anyone is concerned about calcium precipitation, I would suggest pH be at 7.5 or perhaps a little lower and that should eliminate any precip issues.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Adjusting pH and CH?

    Raising both CH and either PH or TA at roughly the same time can lead to calcium clouding if the CH level is on the high side to start with. This should almost never be a problem when all of the levels are in their normal ranges.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    AClogston's Avatar
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    Re: Adjusting pH and CH?

    Cool, that's makes my life a little easier. The pH usually runs a little low due to the Trichlor, and the calcium is on the lower end too so that seems like it shouldn't be an issue.

    Thanks for the info!
    -Alex
    Outdoor Chlorine Pool/Spa (~100' from pump room):(35,000gal IG, plaster, 2 Triton TR-140 sand filters, 2 2HP pumps),(1,200gal IG, plaster, Triton TR-140, 2.5HP pump [circ.], 2 2HP pumps [jets])
    Indoor Bromine Pool/Spa:(24,000gal, plaster, Triton TR-100, 1.5HP SVRS-equipped pump),(3,200gal w/ 3 waterfalls, plaster, Sta-Rite System 3 cartridge filter, 3HP pump [circ.], 3HP pump [jets])

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