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Thread: Difference in PH readings

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    Difference in PH readings

    I have been taking my water to the pool store for testing and have recently started self testing with a HDX 5-way kit from HD. I tested prior to going to the pool store and my PH was calling for 1 pint of acid. I have it tested and they tell me its at 8.0 and needs 2 quarts. Am I just testing it incorrectly or what??? I would like to start just doing it all myself.

    Also I have high calcium hardness and the store convinced me I needed 2 bottles of salinity stain control at 25 bucks a pop. I just don't want to be taken for a ride based on my inexperience. (new pool owner)
    Completed Dec 15. 19000 gal in ground salt, marcite marquis plaster, Pentair Intellichlor ic40, Intelliflo 3hp var.speed, cartridge filter, Ultratemp heat pump 120

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    Mod Squad JVTrain's Avatar
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    Re: Difference in PH readings

    The best thing you can do for your pool is to get a full, recommended test kit. Check out our test kit recommendations: Pool School - Test Kits Compared The TF-100 is the best kit available, from tftestkits.net

    Relying on pool store testing is not recommended here for a few reasons. The top reasons being that their test results are typically not very accurate and simply designed to extract money from your pocket book. Get you in the store then sell you things that you may not actually need.

    I would not purchase any chemicals until you have your own test kit for accurate home testing. Then if you post results here, we can help guide you to learn what your pool needs. Usually for much less money than you'd spend at the pool store.

    Check out the articles in Pool School to get the basics starting with ABCs of Pool Water Chemistry. There is a wealth of information in Pool School.

    Welcome to TFP!
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

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    Re: Difference in PH readings

    So I gather the test kit I have is not adequate?
    Thanks for the help , I will start getting an education in poolschool and see if the marvels of pool chemistry become clearer!
    Just seems I have been battling high PH and low TA last month or so. Ill order a T100 and see what happens.
    Completed Dec 15. 19000 gal in ground salt, marcite marquis plaster, Pentair Intellichlor ic40, Intelliflo 3hp var.speed, cartridge filter, Ultratemp heat pump 120

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    Mod Squad pooldv's Avatar
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    Re: Difference in PH readings

    Is it a drop based kit or a test strip? If it is test strips then throw it away. New plaster pools are prone to having rising PH, SWGs also contribute to rising PH. It can take a year or so for PH to settle down in a new plaster pool. It is IMPORTANT to k3ep the PH below 8. When PH rises above 7.8 add acid to lower it to 7.2-7.5.

    What is your TA? PH will be more stable with TA between 60 and 80. The action of adding acid to lower PH will slowly lower your TA over time until TA and PH reach equilibrium. Or, if your TA is high, above 110 or 120, then you can aggressively lower your TA with this process, Pool School - Lower Total Alkalinity

    Edit:
    Oops, just reread your last sentence that says your TA is low. What is the number? It probably isn't low if your PH is rising rapidly.
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    Texas Splash's Avatar
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    Re: Difference in PH readings

    I also support the TF-100 test kit .... along with the magnetic "Speed Stir" to mix like a pro. You won't regret it.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Mod Squad JVTrain's Avatar
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    Re: Difference in PH readings

    It does seem daunting at first as there is a lot of information. But when you start putting the methods taught here into practice, it becomes much clearer and you'll very soon know more about pool chemistry than nearly every pool store employee.

    Routine testing and sticking to TFP advice while ignoring the pool store is a recipe for success.

    Love that SpeedStir as well. Not only does it make testing more fun, it's more reliable as you can test faster... well at least with less wrist exercise from shaking tubes!
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

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    borjis's Avatar
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    Re: Difference in PH readings

    Thats a home depot pool test kit...very basic...too basic if you want reliable testing.

    Get the TF-100 or Taylor K2006, then you will know precisely whats going on.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
    Dolphin E10 Cleaning Robot.

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    Re: Difference in PH readings

    Ralph,

    One newbie to another (looks like I joined a month or so before you). I had two pH kits before I got my TF-100, one came with the pool and one was in the house when I moved in, I think the PB left it here. One of them was an HDX but I threw them both out after a little closer examination. I did some testing and realized the Taylor is far superior, certainly for me and probably for most people. Here's how I came to that conclusion:

    PH is very difficult for me in the first place as I've discovered I have a slight sex-linked color blindness in the color ranges for 7.5-8.0 on the Taylor color chart after an Expert on this site suggested the possibility. When I looked at the color comparator of the 3 units only the Taylor had colors that were discernibly different for me. I still had some trouble so I bought a portable digital PH test meter for about $20 and some pH 7 calibration solution (I'm a little obsessed with this chemistry stuff!). In my test comparisons of the 3 different test kits, the Taylor results were almost dead on with the calibrated meter and never off more than .1 PH unit. The others were way off (.4 or more) or were not discernible at all in the range. I've found I've been able to "train" myself with some good guidance from members here and the meter. Every time I check the meter now just verifies my Taylor drop test. I would have never guessed there was this much difference. The units all look about the same and I always thought they were indeed the same just packaged differently... turns out I was dead wrong on that!

    So who'd of thunk it that I'd not only learn how to maintain and test my pool but I'd also learn about my own genetics? It's amazing what you can learn here!!

    I hope this helps.

    Chris
    -Chris-
    2013 In-ground plaster/pebble, screen enclosed, 12000 gal w/ Jandy 2 speed 1 HP pump, Jandy CS 200 cartridge filter, 800 gal spa w/ 1.5 HP booster pump, Solar heater, 2 LED lights in pool 1 light in spa, TF-100 test kit, The PoolCleaner Next Generation, Jandy RS-12 Automation system with iAqualink 2.0 control, Separate Hayward/Goldline Solar control

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    Re: Difference in PH readings

    The TF 100 kit is on the way. So 60-80 TA is best? Also when it is calling for acid is it best to add gradually over time (days) or dump the whole amount required at one time?
    Completed Dec 15. 19000 gal in ground salt, marcite marquis plaster, Pentair Intellichlor ic40, Intelliflo 3hp var.speed, cartridge filter, Ultratemp heat pump 120

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    Re: Difference in PH readings

    Pooldv. Just tested using HDX and PA was 7.3 and TA at 90. Added 4 cups since I got the 8 reading from poolstore. I wouldn't think 4 cups would drop it that much. Bring on the TF 100 for some trustworthy readings!!
    Completed Dec 15. 19000 gal in ground salt, marcite marquis plaster, Pentair Intellichlor ic40, Intelliflo 3hp var.speed, cartridge filter, Ultratemp heat pump 120

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    Mod Squad pooldv's Avatar
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    Re: Difference in PH readings

    +1 to a good kit! You'll be a pro in no time.

    It is fine to add all of the acid at once, slowly in front of a pool return, to lower PH from 7.8 to 7.5 or even 7.2. It is important to keep PH between 7.2 and 7.8 at all times.

    Here is a nice page about water chemistry in saltwater pools, Pool School - Water Balance for SWGs
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Richard320's Avatar
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    Re: Difference in PH readings

    Quote Originally Posted by Ralphie99 View Post
    The TF 100 kit is on the way. So 60-80 TA is best? Also when it is calling for acid is it best to add gradually over time (days) or dump the whole amount required at one time?
    It depends... If the pH is off the scale, you might need several applications of acid to bring it down into range. Myself, I think if I needed massive quantities of acid, I'd add no more than half a gallon at a time to bring pH down and let the water mix for a day before the next addition.

    If you're asking about how much acid you'll need to lower TA, stop. TA is the very last thing you worry about. Unless you're at serious risk of Calcium scale, there's no reason to obsess over the TA value. If you keep the pH in line, TA will come down of its own accord over time. Realistically, TA has its main value in poolmath to calculate the acid dose for pH adjustment.

    Go experiment with it. Plug in your numbers. See how much acid is called for. Then raise current TA 40 points and see what happens to the dosage. Lightbulb moment? Now go back and reset everything properly and see what the acid dose should be. Scroll way down to the bottom where it says Effects of Adding Chemicals and see what effect the recommended dose of acid will have on the pool chemistry. Ta will drop with the pH. How about that! Like I said, just keep maintaining pH in range and TA will slowly go down over time. At some point, you'll hit the sweet spot for your pool where the pH will stay stable for a week or more. Wherever that is, that's your target TA. Everybody's pool is slightly different.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Difference in PH readings

    In the rare event I need to add Acid, I fill a 2 gallon bucket half with water then slowly, carefully pour in the
    acid then give it a good stir, before slowly pouring 1 foot in front of the deep end return while the pump is running.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
    Dolphin E10 Cleaning Robot.

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