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Thread: Calcium hardness: Which results are correct?

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    Calcium hardness: Which results are correct?

    I have been using TF100 for two years. Recently, my Calcium Hardness has crept up to 430ppm. I took a sample to two different Leslies and Warehouse Pool Supply stores (four stores total). All have given me values in the mid 200's.

    Confused, I ordered fresh TF100 test chemicals, followed the procedure exactly, and continue to come up in the 430ppm range with TF100. I took another sample to one of the Leslies today, and they came up with 220ppm.

    I don't know what to think. It is hard to refute the preponderance of results from the pool stores; however, I also know from this forum that pool stores are notoriously inaccurate!

    Is there a way to home-make a "standard" solution to test against my TF100? Something like add Calcium Hardness increaser to distilled water in a known quantity, dissolve it, and then run it on TF100? If so, what ratio would I use.

    Please help! Thanks,
    Jay
    17K saltwater, freeform pebbletec with spa; Hayward cartridge filter, Hayward Northstar 2.4HP 2-speed pump, Hayward H400 heater. Hayward T-CELL-15 salt cell.

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    Mod Squad jblizzle's Avatar
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    Re: Calcium hardness: Which results are correct?

    Generally you are best off trusting your own testing ... seems repeatable to me. Do you have the Speedstir? It can help with the CH test especially.

    What does your tap water test at?

    There probably is a way to make a standard solution, but I do not know it.
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    Re: Calcium hardness: Which results are correct?

    Reagent R-7063 is a CH standard solution that will yield a result of around 200 ppm. It's in stock in an 8 oz bottle.
    Dave S.
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    Re: Calcium hardness: Which results are correct?

    If you are using a speedstir, I'd trust your readings first.

    As an aside, it doesn't really matter if you get 430 or 425 or 450, the differences won't affect CSI that much. So use a 10 ml sample and make each drop count as 25. It saves R-0012, as well as you wrist, unless you have a speedstir, in which case your wrist won't care. Directions are in extended-test-kit-directions-t25081.html
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: Calcium hardness: Which results are correct?

    Even if you do not have a speedstir, you can trust your own readings first. Give plenty of time, and ample swirling of the test sample between drops near the end.
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    Re: Calcium hardness: Which results are correct?

    Thanks to everyone for their input! I ordered the standard R-7063 as recommended. This is the 200ppm calcium hardness standard. Here are the results:

    TF100 showed 200ppm right on the money!

    Good news is I was not going insane on my testing. Bad news is I need to drain down the pool some to bring my hardness more in check.

    Learning: POOL STORES DO NOT HAVE A CLUE. Do not trust their testing.
    17K saltwater, freeform pebbletec with spa; Hayward cartridge filter, Hayward Northstar 2.4HP 2-speed pump, Hayward H400 heater. Hayward T-CELL-15 salt cell.

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    Mod Squad jblizzle's Avatar
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    Re: Calcium hardness: Which results are correct?

    430ppm is really not high enough that you need to immediately drain water to lower it. Just keep the pH in range (< 7.8) and you should be fine. Richard320's CH is regularly over 1000ppm.
    Jason, TFP Moderator
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    Re: Calcium hardness: Which results are correct?

    As jbliz said, 430 ppm CH is not something to knee-jerk drain for. Post the rest of your test numbers, especially: ph, TA, cya, salt levels (if you purposefully add it), and borates (if you purposefully raised them).

    What pool surface type do you have? Better yet, put your pool and equipment details into your signature.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: Calcium hardness: Which results are correct?

    Quote Originally Posted by jblizzle
    430ppm is really not high enough that you need to immediately drain water to lower it. Just keep the pH in range (< 7.8) and you should be fine. Richard320's CH is regularly over 1000ppm.
    Not regularly - it's peaked up around 1100. It's usually hovering around 800. I sure hope we have a rainy winter here.
    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: Calcium hardness: Which results are correct?

    Current tests:
    pH: 7.8
    FC: 9
    CC: 0
    TA: 80
    CH: 430
    CYA: 60
    Na+: 3100
    Volume: 17k, including spa
    Chlorine: Saltwater. Hayward T-CELL-15 generator
    Surface: Pebbletec
    Heater: Hayward H400
    Pump: Hayward Northstar 2.4HP, 2 speed. Runs 24h on low speed.
    Filter: Hayward cartridge.
    Location: Houston, TX. Pool runs low 90's in summer.

    Other: Tap water is 100ppm CH

    Questions:
    --At what pH does things go wrong with high Ca+? (and how will I know since I can't look in the pipes!)
    --What is the trigger for draining down the pool and lowering Ca+?
    17K saltwater, freeform pebbletec with spa; Hayward cartridge filter, Hayward Northstar 2.4HP 2-speed pump, Hayward H400 heater. Hayward T-CELL-15 salt cell.

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    Re: Calcium hardness: Which results are correct?

    Nothing in your test results suggest you need to drain.

    Quote Originally Posted by jay42k
    -At what pH does things go wrong with high Ca+? (and how will I know since I can't look in the pipes!)
    It has to do with the "Calcite Saturation Index" (CSI) which is an index to determine risk of scaling which you can read about here: http://www.troublefreepool.com/pool-...alcium_scaling CSI depends on many factors, So you can be high on some things, but that can be mitigated by keeping other things lower. In your case, your CH is just a little high, but your TA is good (fairly low) at 80 ppm...so it counteracts the slightly high CH. Right now, if your pool temp is 80F, then your CSI is +0.11 (CSI lower than -0.6 or higher than +0.6 should be addressed).

    Quote Originally Posted by jay42k
    -What is the trigger for draining down the pool and lowering Ca+?
    Answer is above...but basically CSI above +0.6 without the ability to keep ph and TA low enough.

    How old is your pool?

    Have you been using calcium hypochlorite (cal-hypo) to chlorinate?
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: Calcium hardness: Which results are correct?

    Quote Originally Posted by linen
    Right now, if your pool temp is 80F, then your CSI is +0.11 (CSI lower than -0.6 or higher than +0.6 should be addressed).
    I watch my CSI religiously when I test, using the online pool calculator from TFP's website. It has never exceed +0.6. This summer, it varied in the +0.25 to +0.5 range prior to adjusting pH. Once I added acid, it would bring CSI down to -0.1 or so
    Quote Originally Posted by linen
    How old is your pool?
    2 years
    Quote Originally Posted by linen
    Have you been using calcium hypochlorite (cal-hypo) to chlorinate?
    No. I use a SWG to generate chlorine.
    17K saltwater, freeform pebbletec with spa; Hayward cartridge filter, Hayward Northstar 2.4HP 2-speed pump, Hayward H400 heater. Hayward T-CELL-15 salt cell.

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    linen's Avatar
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    Re: Calcium hardness: Which results are correct?

    Sounds like you have a good handle on it then

    It maybe that your CH is slightly higher (again, it really isn't very high) from when your pool was built.

    Since you have a swg, it is not a bad idea to run the csi a little lower (slightly negative) to prevent the cell from scaling. Also, you may want to consider 50 ppm borates if you regularly do have cell scaling. This doesn't happen to everyone, but if you see white flakes coming out of a return, that could be signs of scaling in your cell.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: Calcium hardness: Which results are correct?

    I wanted to second this. I went to Leslie's today my own CH reading shows that I am at 490 PPM while the guy tells me that I am sitting at 240. Anyway he was off on my FC and everything else... It is pointless to take your water there.

    Sorry to high jack this one. But, what test is best for checking phosphate levels? Just the Taylor phophate test or the strips by Aquacheck? I am asking because I do not want to trust the Leslie's results. Also what is best way to treat phosphate? I ask because we have huge Agriculture here and the winds bring some fertilizer and more with them.

    Also how accurate our the Aquacheck test strips for salt? I am reading 4700 from my own testing when the store was stating it is 3700.
    12700 gallons
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    plaster
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    Pentair Whisperflo single speed pump WFE 4 (1 HP)
    Built in 2005
    SWG equiped, Zodiac LM2-24
    CH 340, PH 7.8, FC 8.5, TA 90, CYA 80, SALT 4000, CC 0

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    Re: Calcium hardness: Which results are correct?

    It is generally recommended to ignore the phosphate level. It doesn't matter how much "algae food" is in the water if the chlorine level is kept high enough to prevent algae from living in it. Is there another effect that you're concerned about from the presence of phosphates?
    Outdoor 14,000 gallon IG plaster pool built in 2000 with spillover spa, 2 hp WhisperFlo pump with MagneTek motor, Sta-Rite cartridge pool filter with 300 ft2 filtration area and 0.33 gpm/ft2 filtration rate, Aquabot Rapids 4WD robotic pool cleaner, Raypak digital gas heater, and Intermatic mechanical timer located in the Dallas-Fort Worth metroplex

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    Re: Calcium hardness: Which results are correct?

    I did not know. No I was mainly worried about the Algae. I have been told by the pool store people and others that one should keep the phosphate level down to avoid using up the chlorine too quickly specially if one uses SWG. That is why I was concerned. So to confirm again I should not worry about checking my phosphate levels ever?
    12700 gallons
    IG pool and spa
    plaster
    Sand Filter Pentair Titan II
    Pentair Whisperflo single speed pump WFE 4 (1 HP)
    Built in 2005
    SWG equiped, Zodiac LM2-24
    CH 340, PH 7.8, FC 8.5, TA 90, CYA 80, SALT 4000, CC 0

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    Re: Calcium hardness: Which results are correct?

    Yep, ignore the phosphate level. Most folks here never test for it. Running your SWG (or adding bleach for those of us who don't choose to run an SWG) to keep the FC level where it needs to be based on CYA is the best and cheapest way to prevent algae.

    Follow the guidelines for an SWG pool, and you'll be fine: pool-school/recommended_levels. Also see: pool-school/chlorine_cya_chart_shock for the recommended FC level based on CYA (look at the chart for SWG in this one, too).

    Finally, if you want more on phosphates and their unimportance for trouble-free pools, use the search at the top of the page and type in "phosphate". There is a thread where JasonLion and chem geek got into some of the complexities if you're looking for the detailed reasoning on the subject. You can find it here: phosphates-1000-to-worry-or-not-to-worry-t41602.html.
    Outdoor 14,000 gallon IG plaster pool built in 2000 with spillover spa, 2 hp WhisperFlo pump with MagneTek motor, Sta-Rite cartridge pool filter with 300 ft2 filtration area and 0.33 gpm/ft2 filtration rate, Aquabot Rapids 4WD robotic pool cleaner, Raypak digital gas heater, and Intermatic mechanical timer located in the Dallas-Fort Worth metroplex

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    Re: Calcium hardness: Which results are correct?

    Also how accurate our the Aquacheck test strips for salt?
    plus or minus 400 is a guideline on accuracy. Most people report slightly more accurate results, though.

    Check the expiration date on them. There is some good anecdotal evidence that they get pretty erratic when they expire.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Calcium hardness: Which results are correct?

    Thank you both. I will forget about phosphate then because I read the info. on the link and seems to make absolute sense.

    The salt test has a expiry of 12/2014. I was wondering whether I should buy the Taylor salt test instead. Are people getting more accurate results with those?
    12700 gallons
    IG pool and spa
    plaster
    Sand Filter Pentair Titan II
    Pentair Whisperflo single speed pump WFE 4 (1 HP)
    Built in 2005
    SWG equiped, Zodiac LM2-24
    CH 340, PH 7.8, FC 8.5, TA 90, CYA 80, SALT 4000, CC 0

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    Re: Calcium hardness: Which results are correct?

    The Taylor drops based test has an accuracy of plus or minus 200 ppm and, I've never done the math, but is probably cheaper per test than the Aquacheck strips
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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