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Thread: need some chemical help

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    need some chemical help

    Hi all, I haven't been to my CPO class yet, so when I noticed that my automated chemtrol feeders were adding endlessly and the pH and ORP weren't changing, i tested the alkilinity and found it was too high. i added HCl and now the alkalinity has stabilized but the feeders still won't change the pH or ORP. this has happened with both the spa and the lap pool which is 20' by 8' (roughly 18,000 gallons). both pools had high alkalinity and i'm fairly certain i added too much acid. but the spa water still has a green tinge and last night somebody was in it without my knowledge, they reported skin irritation and their swim trunks went from blue to grey. i get a smell of chlorine around the spa. the lap pool is completely clear now but the feeders still wont change the levels. does anyone know what i may have done and how i can fix it?

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    JasonLion's Avatar
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    Re: need some chemical help

    Welcome to TFP!

    The first step is to get a complete set of water test results and post them, also tell us what kind of test kit you are using.
    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: need some chemical help

    The pH and ORP probes could be bad.
    Over 30 years in the pool business
    We build vinyl, fiberglass, stainless steel pools
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    Re: need some chemical help

    Thanks, I'm using the Taylor complete test kit. The pH tests at 7.4. For the chlorine I'm using LaMotte testabs and a neutralizer found in the kit, but the tabs completely dissolve and it reads as no chlorine in the spa. The alkalinity test goes from blue to yellow not green to red (I read somewhere that this means there's too much chlorine) and reads at 40ppm. Calcium hardness reads at 40 ppm. Could not get a reading for the cya test, black dot was visible when whole sample was used

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    Re: need some chemical help

    It's funny you mention the probes because I'm cleaning them now haha

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    JasonLion's Avatar
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    Re: need some chemical help

    All of your results are consistent with FC being extremely high. The LaMotte tabs bleach out at high FC levels and falsely report FC as zero, and the color change you saw with the TA test is exactly what happens with high FC levels.

    That points to the ORP probe being fouled, as swimcmp already suggested, or the PH being way out of range.

    I'm worried about the the PH level. Very high FC levels can throw off the PH test. It isn't clear just how high your FC level has gotten. FC must be at least 10, probably more like 20+ to get the TA colors you saw. If FC is only 10-18 then the PH test is close enough and shouldn't be a problem, but FC above 18 is likely to cause the PH test to be way off of reality. As the FC level comes down the PH test will return to working, which might reveal some correction needed to PH. I'm not sure what will happen, but at a minimum you should monitor the PH as the FC level comes down and watch for sudden changes in the PH reading.

    I assume this is an indoor pool? Given that, you probably want to use some chlorine neutralizer to get the FC level back below 10 where your test can read the FC level.

    You didn't describe the green tinge, but assuming it is a clear transparent green and not a cloudy/murky green, that is also consistent with the FC Level being very high. High FC levels tend to cause any metals in the water to change into a form that colors the water.
    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: need some chemical help

    It's actually an outdoor spa but yea that's what I was thinking because I added a little bit of chlorine neutralizer and the pH shot down and the ORP shot up. I've closed the spa for now I'm not letting anyone in until its fixed. It seems to have stabilized now, but I'm wondering if that's only because the amount of neutralizer I added has already been eaten up

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    Re: need some chemical help

    And yea it's a clear transparent green but that's starting to fade a little

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    Re: need some chemical help

    You were right to be worried. The pH is below 5 which is kinda what I figured unfortunately. Should I drain it and put new water in?

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    JasonLion's Avatar
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    Re: need some chemical help

    You can drain, or adjust the PH, both take a bit of work. Spas generally have the water replaced regularly, and if it is nearly time to replace the water anyway that is clearly the best approach. On the other hand, raising the PH in a spa isn't all that difficult though it does take a bit of paying attention during the process so you don't overshoot, just raise the TA a bit and run the jets and the PH should come right up.
    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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