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Thread: Purple pH Indicator

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    Modawg2k's Avatar
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    Purple pH Indicator

    Hey Guys, my hot tub is a bit out of wack and I was curious what my next step would be. I just drained & refilled a few weeks ago so I'd really like to try and avoid doing another drain.

    At some point in the past few weeks, I lost track of both my bromine level and pH. The pH indicator in my k-2006 currently turns purple when I test it. I did baking soda a week ago because my water was around 7.0 and now it's the purple color. My bromine level on a stick registers dark green (above 20ppm). I tested for bromine on the k-2006 by measuring FC, but FC comes back at 0, with only some slight discoloration around the DPD powder sitting at the bottom of the tube. What should my next step be?

    Much appreciated.
    ~15k gallons, 3'-5'-4' Figure 8 Shape In Ground
    Wetedge Satin Matrix Interior (Pebble)
    Paramount In-floor System
    Pentair IntelliFlo VS 3050, Pentair Triton II TR100 Sand Filter
    Pentair Intellichlor IC40 SWG

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    Richard320's Avatar
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    Re: Purple pH Indicator

    I'd guess your bromine level is just plain too high. I know with chlorine, high levels react with the phenol red indicator and tend to shift the color towards purple, so I assume bromine does the same. Here's an older thread with some pictures that are a good indicator of it: http://www.troublefreepool.com/threa...els-with-R-007

    If the FAS-DPD test turns color for a second, but clears, try adding another scoop of powder. You might be actually bleaching out the dye.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: Purple pH Indicator

    I agree with Richard, high bromine causing a false high pH color. Double check the bromine level with 2 scoops of FAS-DPD powder to confirm.

    What is your current alkalinity?

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    Modawg2k's Avatar
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    Re: Purple pH Indicator

    Thanks for the input.* Are there any non-drain methods to decrease bromine?* Can I just let the water soak up the sun rays to breakdown the bromine? *I will have to check TA later.* I didn’t test for that because I assumed it would be invalid like the pH reading was.*
    ~15k gallons, 3'-5'-4' Figure 8 Shape In Ground
    Wetedge Satin Matrix Interior (Pebble)
    Paramount In-floor System
    Pentair IntelliFlo VS 3050, Pentair Triton II TR100 Sand Filter
    Pentair Intellichlor IC40 SWG

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    Re: Purple pH Indicator

    You can use sodium thiosulfate to lower bromine, but it's usually better to allow the sun to bring it down. The TA test should be valid, but it the colors will be off (blue to yellow vs green to red). Just go by the color change. Sometimes it's better to drain and refill than to try to recover from really bad chemistry.

    Have you tried redoing the fas-dpd test with extra powder?

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    Modawg2k's Avatar
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    Re: Purple pH Indicator

    Thanks guys for the responses.
    I added more powder and my chlorine/bromine levels were definitely readable.

    My numbers
    FC: 8
    Calculate Br (x2.25): 18
    pH: still purple
    TA: 110-120

    Think the water is still salvageable with letting the Bromine get consumed a little thru sunlight?
    ~15k gallons, 3'-5'-4' Figure 8 Shape In Ground
    Wetedge Satin Matrix Interior (Pebble)
    Paramount In-floor System
    Pentair IntelliFlo VS 3050, Pentair Triton II TR100 Sand Filter
    Pentair Intellichlor IC40 SWG

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    Re: Purple pH Indicator

    You should be ok waiting for the sunlight to reduce the bromine. Based on the TA, I think that your pH is probably high. I think that you could use 8.0 as the starting pH and 7.5 as the target pH in poolmath. Retest pH after the bromine comes down a little.

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    Modawg2k's Avatar
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    Re: Purple pH Indicator

    Update: I left the cover off all day, and I added acid based off the pool math for the spa. Here are the numbers

    FC: 1
    Br (calculated): 2.25
    ph: <7.0
    TA: 80

    So now that my bromine levels aren't too high, time to tackle pH. What is considered the best method for doing this?
    ~15k gallons, 3'-5'-4' Figure 8 Shape In Ground
    Wetedge Satin Matrix Interior (Pebble)
    Paramount In-floor System
    Pentair IntelliFlo VS 3050, Pentair Triton II TR100 Sand Filter
    Pentair Intellichlor IC40 SWG

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    JasonLion's Avatar
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    Re: Purple pH Indicator

    Aeration will probably do it, but if that doesn't take care of it then some borax (or soda ash if you already have it).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Purple pH Indicator

    Your TA dropped by 30 to 40. Using 400 gallons for the spa, you should have added about 0.6 oz of acid, which should have lowered your TA by about 6 ppm. You added about 5x too much acid.

    You might need to recheck your volume and other calculations.

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    Modawg2k's Avatar
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    Re: Purple pH Indicator

    I checked w/ Dynasty spas today and they said my spa holds ~425 gallons. So now that I have that number, I will plug that into the math. I probably used too much acid because I use my 30oz cup that I also use to measure chemicals for the pool. I know I should grab a smaller measuring device for the spa. Any handling advice for acid and spas? I feel like it's hard to get the small amount out of the gallon jug that the acid is stored in.
    ~15k gallons, 3'-5'-4' Figure 8 Shape In Ground
    Wetedge Satin Matrix Interior (Pebble)
    Paramount In-floor System
    Pentair IntelliFlo VS 3050, Pentair Triton II TR100 Sand Filter
    Pentair Intellichlor IC40 SWG

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    Re: Purple pH Indicator

    I find it helpful to pour a small amount into a disposable plastic cup and then into the measuring cup. Then you can pour the rest from the disposable cup back into the bottle.

    I also find it to be easier using milliliters to measure such small amounts. There are about 30 ml per oz. So, 0.6 oz would be 18 ml. The pool math tool has a toggle to go from standard to metric units if you prefer to do it that way.

    Spa chemicals can be trickier to handle due to the tiny amounts, especially when you're used to handling pool amounts.

    Note: Don't use anything metal, paper or Styrofoam.

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    Modawg2k's Avatar
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    Re: Purple pH Indicator

    Just when I was getting ready for smooth sailing, the spa has a leak and I've lost half the water. The irony is the leak is from the tube that houses the spa frog cartridges which I don't use anymore. I'm hoping this is an easy fix. uploadfromtaptalk1395072717550.jpg
    ~15k gallons, 3'-5'-4' Figure 8 Shape In Ground
    Wetedge Satin Matrix Interior (Pebble)
    Paramount In-floor System
    Pentair IntelliFlo VS 3050, Pentair Triton II TR100 Sand Filter
    Pentair Intellichlor IC40 SWG

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