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Thread: Is it ok to use HCl to lower PH?

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    Is it ok to use HCl to lower PH?

    I'm a new pool owner, now I only have a cheap 2-ways tester, which can only test TC and PH.
    I just add all the water in to the pool few days ago and set the SWG timer to run for 9 hours a day (3 hours on and 5 hours off).

    Today I just made the first test. The test result is 8.2 PH and 3.0 TC. I try to correct this by adding HCl (Hydrochloric acid) and re-program my SWG timer (from 9 hrs/day to 6 hrs/day). I will test it again tomorrow.

    The pool shop, who sell me all the equipment, said I don't need to add anything other than HCl to lower PH.

    I think I will going out to buy a better test kit, but I'm not so sure about the HCl, Is it ok to use?

    My pool is outdoor and subject to direct sunlight about 8 hours a day.
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    -26 Cubic Meters (6,868 Gallon) On Ground Concrete pool with epoxies paint finished.
    -EMAUX FSF 400-6W Sand Filter&Pump Combo 6.48 Cubic Meters/Hour (1,711 Gallon/Hr)
    -EMAUX SSC15-T Salt Chlorinator (Cell output 15 g/hr)

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    JasonLion's Avatar
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    Re: Is it ok to use HCl to lower PH?

    We tend to use the name muriatic acid, since it is usually sold under that name, but technically it is hydrochloric acid. Exact same stuff, just two different names. Whatever you call it, this is the kind of acid we recommend for lowering PH.
    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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    Re: Is it ok to use HCl to lower PH?

    Quote Originally Posted by ting
    I think I will going out to buy a better test kit...
    Yes, a good test kit is very important. The only choices worth buying are the Taylor K-2006, or TF-100. Both of these can be bought from tftestkits.net.
    John
    7 year old ~13,500 gal 24' AGP with 1.5 hp Proline pump, 150 sqft Pleatco cartridge, filled with well water with pH of about 4.5.
    Wanda the Whale pool vacuum, home made heater, Taylor K-2006
    Cloudy Pool? 1) Order test kit. 2) Follow SLAM
    New to TFPC? Read Pool School a few times, then post questions. PoolMath will help with chemical additions.

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    Vette's Avatar
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    Re: Is it ok to use HCl to lower PH?

    Beautiful pool! We recommend the TF-100 test kit, as John posted above.
    11,700 gallon 21' round 54" deep all-resin AGP - June 2012
    Waterway 1HP 2-speed pump / 100 sq ft cartridge filter
    Hayward 150,000btu Natural Gas heater
    I use and recommend the TF-100 for testing

  5. Back To Top    #5

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    Re: Is it ok to use HCl to lower PH?

    I just order the TF-100 test kit and the automatic stirrer, it might take few week to arrived.

    Today I just test my pool again with the 2-way test kit. The PH still over 8.2 but TC is drop below 1.0.
    I think I will have to add more HCl.
    -26 Cubic Meters (6,868 Gallon) On Ground Concrete pool with epoxies paint finished.
    -EMAUX FSF 400-6W Sand Filter&Pump Combo 6.48 Cubic Meters/Hour (1,711 Gallon/Hr)
    -EMAUX SSC15-T Salt Chlorinator (Cell output 15 g/hr)

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    Re: Is it ok to use HCl to lower PH?

    A pool with multiple spillovers and with a saltwater chlorine generator will have a lot of aeration so a lot of carbon dioxide outgassing and that causes the pH to rise. You probably need to lower your Total Alkalinity (TA) which may help to reduce the rate of pH rise and especially the amount of acid you need to add. If you can get boric acid, then adding 50 ppm Borates can provide additional pH buffering. See Water Balance for SWGs.
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Is it ok to use HCl to lower PH?

    Yes, go ahead and add more HCl. You want your pH between 7.2 and 7.8.

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    Re: Is it ok to use HCl to lower PH?

    While I'm waiting for the TF-100 test kit to arrived. I call local pool shop and ask if they have CYA. They don't know what I'm talking about and ask me to hold the line. They return and told me that they have some kind of chlorine powder called "Trichloroisocyanuric acid powder 90%". Is this the CYA your guy talking about?
    -26 Cubic Meters (6,868 Gallon) On Ground Concrete pool with epoxies paint finished.
    -EMAUX FSF 400-6W Sand Filter&Pump Combo 6.48 Cubic Meters/Hour (1,711 Gallon/Hr)
    -EMAUX SSC15-T Salt Chlorinator (Cell output 15 g/hr)

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    JasonLion's Avatar
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    Re: Is it ok to use HCl to lower PH?

    No, that is what we call trichlor.

    CYA is sold under several names: cyanuric acid, conditioner, stabilizer, etc.
    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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    Mod Squad Bama Rambler's Avatar
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    Re: Is it ok to use HCl to lower PH?

    CYA is cyanuric acid or commonly referred to as stabilizer or conditioner. You really don't want to add any CYA until you're sure what the level is now.
    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: Is it ok to use HCl to lower PH?

    It seem like I can't find CYA here in Thailand. Try to call all the pool shop around and the answer is they don't know what I'm talking about. Try to call Chemical shop and found one have isocyanuric acid in stock, but they sell it in bulk of 25 Kilogram (50 pound).

    So I'm thinking about using "Trichloroisocyanuric acid powder 90%" instate. Is that ok?
    -26 Cubic Meters (6,868 Gallon) On Ground Concrete pool with epoxies paint finished.
    -EMAUX FSF 400-6W Sand Filter&Pump Combo 6.48 Cubic Meters/Hour (1,711 Gallon/Hr)
    -EMAUX SSC15-T Salt Chlorinator (Cell output 15 g/hr)

  12. Back To Top    #12
    JasonLion's Avatar
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    Re: Is it ok to use HCl to lower PH?

    Trichlor also contains chlorine. Using enough to raise the CYA level a reasonable amount will raise the FC level rather too much. You can get around that by spreading your trichlor additions out across a number of days. It ends up being noticeably more effort, but it will work.
    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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