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Thread: Which tests affected by high FC?

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    Saturn94's Avatar
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    Which tests affected by high FC?

    I know the pH test is adversely affected by FC over 10ppm, but how about the other tests we normally do, plus borates via Lamotte strips and salt via AquaCheck strips (I use Taylor kits for everything else)?
    20k IG vinyl liner/Aqua Rite SWCG, T-15 cell/Hayward Pro Grid 6020 DE filter/Polaris 280 with booster pump/Hayward Superpump 1 hp/city water/pool installed March 2004

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    Re: Which tests affected by high FC?

    Quote Originally Posted by Saturn94 View Post
    I know the pH test is adversely affected by FC over 10ppm, but how about the other tests we normally do, plus borates via Lamotte strips and salt via AquaCheck strips (I use Taylor kits for everything else)?
    If the FC is really high (like shock levels), the the TA test can be affected. The colors will not be green/red but more like a yellow/pink because the dye gets bleached by the chlorine. That's why, even at normal FC levels, you have to add the R-0007 to dechlorinate the water sample. I probably wouldn't do the CH test either because of that issue. I'm not sure what the LaMotte boron test strips use for chemistry but the mannitol/bromothymol blue titration test that I use definitely needs to be dechlorinated like the TA test or else the dye gets completely bleached out. AquaCheck strips test for salt by measuring the capillary action of water up a column. I don't FC affects that much but, then again, I've never liked those strips and much prefer the K-1766 test which is mostly immune to higher chlorine levels. The CYA test is generally unaffected by high FC as the reagent buffers the test sample to a very low pH value where the melamine/cyanurate complex is more likely to form. Chlorine can affect the formation of the complex but you'd have to be at extraordinarily high FC levels (well over shock levels) to notice it.
    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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    Re: Which tests affected by high FC?

    None. pH is the only one.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Saturn94's Avatar
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    Re: Which tests affected by high FC?

    Thanks. I should have mentioned I was thinking about the effect at recommended shock levels.

    Right now My FC is at 20ppm with CYA at 50 (I just finished a SLAM this morning). I was wondering what other levels I could check and adjust now and which I need to wait until FC drops to normal (or at least under 10ppm?).

    Looks like I can go ahead and test/adjust salt and CYA, but hold off on TA, CH, and possibly borate? Is that correct?
    20k IG vinyl liner/Aqua Rite SWCG, T-15 cell/Hayward Pro Grid 6020 DE filter/Polaris 280 with booster pump/Hayward Superpump 1 hp/city water/pool installed March 2004

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    Re: Which tests affected by high FC?

    Since you can't measure pH accurately at your FC level, I would not adjust anything that could affect pH. I'll assume your water is cold and not generating chlorine at the T-15 cell but I would turn off the SWG until your FC comes down.
    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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    Re: Which tests affected by high FC?

    Quote Originally Posted by JoyfulNoise View Post
    Since you can't measure pH accurately at your FC level, I would not adjust anything that could affect pH. I'll assume your water is cold and not generating chlorine at the T-15 cell but I would turn off the SWG until your FC comes down.
    pH was 7.2 before I started the SLAM. Water temp is currently 66 (up from 61 yesterday..woo hoo! Lol). SWCG has been off the whole time and will stay off until everything is balanced, including letting FC drift down to normal, and water temp is about 70.

    What adjustment specifically might affect pH?

    I went ahead and added salt today and was going to add CYA, but according to Pool Math 4# of CYA will lower pH 0.44. Funny, I don't remember CYA impacting my pH readings before. I guess hold off on this?
    20k IG vinyl liner/Aqua Rite SWCG, T-15 cell/Hayward Pro Grid 6020 DE filter/Polaris 280 with booster pump/Hayward Superpump 1 hp/city water/pool installed March 2004

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    Re: Which tests affected by high FC?

    Salt is fine.

    CYA....yeah, you need to take those "Affects of Adding Chemicals" calculations with a grain of salt (pun intended) as they assume certain values for TA and starting pH. SO they are not too terrible accurate in predicting the pH change for large additions of chemicals. I doubt 4lbs of CYA will do much at all to your pH. So that one you can adjust.

    Anything else....wait till your FC is down.
    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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    Re: Which tests affected by high FC?

    Quote Originally Posted by JoyfulNoise View Post
    Salt is fine.

    CYA....yeah, you need to take those "Affects of Adding Chemicals" calculations with a grain of salt (pun intended) as they assume certain values for TA and starting pH. SO they are not too terrible accurate in predicting the pH change for large additions of chemicals. I doubt 4lbs of CYA will do much at all to your pH. So that one you can adjust.

    Anything else....wait till your FC is down.
    Got it.....thanks.

    Off to add CYA.
    20k IG vinyl liner/Aqua Rite SWCG, T-15 cell/Hayward Pro Grid 6020 DE filter/Polaris 280 with booster pump/Hayward Superpump 1 hp/city water/pool installed March 2004

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