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Thread: Calcium Hardness question

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    lastdon87's Avatar
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    Calcium Hardness question

    I'm about 2 weeks or so into my new pool and feel like I have a pretty good grasp on the chemicals and testing so far. But I am a little stumped on my calcium hardness. Initially at fill it was 175. I then bought a couple 4 lb containers of pellets that are meant to raise CH, and then I tested it at the 200 level (1 week ago). Now, I test it again today and it says I'm back at 175...? I thought CH doesn't go down unless you do a drain and refill, or add some other chemical to the water?

    My pool is a mini pebble plaster pool and my other members were:

    Ph- 7.5
    FC - 3
    TA- 100
    CYA- 40

    Any help or ideas is welcome...thx y'all!
    34x22 freeform, 94'/20,200 gallons, 3.5' to 6', Mini Pebble Aqua Blue, 8' lagoon shelf(18"), A&A in-floor, Venturi skimmer, A&A channel drain, 3 returns, VS3050 pump, Pentair CC420 filter, AQR 15 Salt System, 1 Intellibrite 5G light, 1 globrite in shelf, Heat Siphon Z575HP, 24" sheer decent, Decking will be stained salt finished concrete

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    borjis's Avatar
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    Re: Calcium Hardness question

    I know my CH & CYA numbers go down if I have a few drain downs because of rain addition.

    Have you had any of that?
    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.
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    Texas Splash's Avatar
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    Re: Calcium Hardness question

    Hello! Two 4-lb containers (128 oz) would take CH from 175 to about 218 for your size pool. Of course there is a slight variance there, but surely slightly over 200. CH should not go down unless you exchanged water which I'm assuming you have not, or have magical fill water in which case everyone in AZ will be at your front door soon with a hose. But you only recorded about 200 a week ago which is a little odd. I wonder if the original 175 reading was a little lower perhaps? Looking in your sig, I don't see what test kit you have. Also, do you have a "speed stir" for easy/efficient mixing?

    And I can't help myself for asking (habit) , but while looking at your sig, I see you have a SWG, but your CYA is quite low for a saltwater pool (70-80 range). Have you considered raising that to protect the FC generated by the SWG? Sorry, I don't mean to change the subject. Just kind of stood-out to me. We'll try to help you with the CH.
    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
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    lastdon87's Avatar
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    Re: Calcium Hardness question

    Quote Originally Posted by Texas Splash View Post
    Hello! Two 4-lb containers (128 oz) would take CH from 175 to about 218 for your size pool. Of course there is a slight variance there, but surely slightly over 200. CH should not go down unless you exchanged water which I'm assuming you have not, or have magical fill water in which case everyone in AZ will be at your front door soon with a hose. But you only recorded about 200 a week ago which is a little odd. I wonder if the original 175 reading was a little lower perhaps? Looking in your sig, I don't see what test kit you have. Also, do you have a "speed stir" for easy/efficient mixing?

    And I can't help myself for asking (habit) , but while looking at your sig, I see you have a SWG, but your CYA is quite low for a saltwater pool (70-80 range). Have you considered raising that to protect the FC generated by the SWG? Sorry, I don't mean to change the subject. Just kind of stood-out to me. We'll try to help you with the CH.
    Thanks for the help, I do have the speed stir and TF-100. I haven't started my SWCG yet since my pool is only a couple weeks old, but yes, I do plan to raise the CYA, just want to take it really slow. Maybe my testing was off some how, I guess I did fill up my pool from closer to the bottom of the tile line to the top of the tile line a couple days ago, maybe that had something to do with it. I'll grab a could more of the 4 lb containers and get it up to around the 250 Mark soon hopefully.

    - - - Updated - - -

    Quote Originally Posted by borjis View Post
    I know my CH & CYA numbers go down if I have a few drain downs because of rain addition.

    Have you had any of that?
    No rain of any significance around here in AZ, but I'll remember that for when the monsoons hit in a few months...
    34x22 freeform, 94'/20,200 gallons, 3.5' to 6', Mini Pebble Aqua Blue, 8' lagoon shelf(18"), A&A in-floor, Venturi skimmer, A&A channel drain, 3 returns, VS3050 pump, Pentair CC420 filter, AQR 15 Salt System, 1 Intellibrite 5G light, 1 globrite in shelf, Heat Siphon Z575HP, 24" sheer decent, Decking will be stained salt finished concrete

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    Texas Splash's Avatar
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    Re: Calcium Hardness question

    Oops. You did say a couple weeks old in your first post. Disregard my habitual rant. I suppose it's very possible that with all the new plaster and dust removal/settling, that it skewed the CH testing a bit - at least the earlier one perhaps. Your minimum recommended level is 250 with no SWG (350 ppm when turned-on), so if you continue to see the same 175-200 results, you might consider increasing just a little for that new plaster. Of course I suspect your fill water is hard which will drive-up CH quickly as well. You might want to test that tap water now to to compare so you get an idea how it will effect the pool. I would simply continue to monitor more frequently than normal (at least once a week or so) until your pool has settled down and you're past the 30-day mark. Then you might be able to back-off CH testing to about every couple weeks or more as needed.
    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
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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    Re: Calcium Hardness question

    Agreeing with others, I would not be in a big hurry to raise your CH. It has a tendency to rise in all pools and will do so more quickly if your fill water is like most everyone in the Southwest. Test your tap water for CH so you know what you are adding.

    As for your discrepancy of 200 - 175, I would just not worry about it......probably a testing error or some other variance. I hope it stays down low for you for a while because I think you will begin to see a slow, steady increase.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    lastdon87's Avatar
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    Re: Calcium Hardness question

    Quote Originally Posted by duraleigh View Post
    Agreeing with others, I would not be in a big hurry to raise your CH. It has a tendency to rise in all pools and will do so more quickly if your fill water is like most everyone in the Southwest. Test your tap water for CH so you know what you are adding.

    As for your discrepancy of 200 - 175, I would just not worry about it......probably a testing error or some other variance. I hope it stays down low for you for a while because I think you will begin to see a slow, steady increase.
    I did test my fill water prior to filling the pool and the CH was 150... and now I'm somewhere between 175 and 200. So, you don't think I should try to raise it up to 250ish? I just don't want it to.be ducking the life out of my new plaster like I've read about... thx to everyone for helping out so quickly!
    34x22 freeform, 94'/20,200 gallons, 3.5' to 6', Mini Pebble Aqua Blue, 8' lagoon shelf(18"), A&A in-floor, Venturi skimmer, A&A channel drain, 3 returns, VS3050 pump, Pentair CC420 filter, AQR 15 Salt System, 1 Intellibrite 5G light, 1 globrite in shelf, Heat Siphon Z575HP, 24" sheer decent, Decking will be stained salt finished concrete

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    JoyfulNoise's Avatar
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    Calcium Hardness question

    I'm up in Tucson. My fill water is 280ppm CH on a good month. You DO NOT need CH increaser here. Believe me, when the hot dry weather kicks in you will be adding so much fill water to your pool that your CH will go up all on its own. Based on pan evaporation data from our area of Arizona, we get an a average of over 100" of water evaporation per year. That means you will evaporate away almost your entire pool volume of water and effectively double your CH.

    As long as you keep your CSI within the TFP ranges that are considered balanced for plaster (-0.3 < CSI < +0.3), your plaster will be fine. For your pool with an SWG, you should aim for a CSI of -0.1 and you can do that primarily through changing your pH and TA while letting your CH just be wherever it wants to be.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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