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Thread: Purple Precipitate

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    Join Date
    May 2017
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    Fairport, NY
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    Purple Precipitate

    Hello all! Thank you in advance for taking time to read about an issue which I am having. Hopefully someone who had a similar issue will be able to offer some insight.

    Background: Last year (2016) at the end of the pool season my heat pump failed. Apparently water got into the system through a breach of some sort most likely due to corrosion of the copper heat exchanger. I don't know how well the previous owners maintained their water. A short while later, the surfaces of the pool got covered by a purple sludge. It's not stained into the vinyl, but is in a very fine type of powdery solid and can be brushed off with a little effort. When brushed it dissipates into the water which turns murky. When my Aquabot cleaner runs, it accumulates the purple sludge in the bag and needs to be cleaned frequently. It also doesn't get it all off the floor and walls.

    It's my understanding based upon research that this is most likely the result of Copper Cyanurate (copper released into the pool from the failed heat pump combining with high levels of cyanuric acid (stabilizer)). My CA level is at 134 ppm which is much too high.. I'm working on lowering the levels of CA by draining the pool down a little and then adding more water in. I was advised against lowering the water too much as the liner can shift.

    I have a few questions..
    1) Is there a better way to lower the CA levels?
    2) Will the purple precipitate disappear as the CA levels decrease or do I need to scrub everything down (something which would be very difficult to do as it takes a some effort to remove and then it just goes back in to the water to potentially resettle elsewhere. I don't know if the filter catches this very fine stuff).
    3) Is there something which can aid in removing the purple precipitate/sludge such as an additive?

    I have just replaced the heat pump with one which has a titanium heat exchanger and I maintain the pool chemistry correctly so this issue will not resurface.
    Dan Cormack
    Pool: 19,000 Gal, IG, Vinyl, Sand Filter (installed 2007), Pentair Model 320 Automatic Chlorine In-Line feeder
    Test Kit: Taylor K-2006

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    JoyfulNoise's Avatar
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    May 2015
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    Tucson, AZ
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    Re: Purple Precipitate

    Vacuum it to waste as best you can. If you know & understand how to use a floc (in other words, follow the directions and water balancing instructions to a tee), then you can try to drop the precipitate using a floc and vacuum it to waste. It's best not to redissolve it otherwise you add that copper back to your water which you do not want anyway.

    - - - Updated - - -

    My guess is the previous owners were probably putting trichlor pucks in their skimmer which can become highly acidic and that rotted out the inside of the heat exchanger. That would also be consistent with the high CYA levels.
    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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    Sep 2016
    Location
    Escondido/CA
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    641

    Re: Purple Precipitate

    Try the tarp approach to draining and refilling. Put a very large tarp over your pool, then drain from under it, put the new water on top of it, and when you get to the right ratio of new to old water, slip out the tarp. You will waste a lot less water that way, and you can get down to your target in one shot.
    Jon -- 28kgal, IG, AquaBright, Attached Spa, ~1990, Quad DE 80, Easytouch8, IntelliFloVS-3050, Intellichlor60, IntelliPh, Dolphin DX6, City Water, K-2006/TF-100, SpeedStir, SampleSizer, San Diego, CA

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    Fairport, NY
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    Re: Purple Precipitate

    Thank you for your responses! I appreciate the helpful advice offered..I don't think the tape idea will work too well for me but it's an interesting idea..
    My approach to handling this is to vacuum to waste as much as possible. This serves the dual purpose of removing / replacing water in order to lower the CYA levels. My pool has an automatic dispenser which uses the 3" tricolor pucks so that's the source of the CYA.
    I'm leaning heavily towards replacing the existing chlorinator with a SWG. All that I have read about this method is positive and I definitely don't want to go through this mess again... ever. I'll update in this thread as things progress around clearing up this purple nightmare. One thing which I ordered was "The Blue Stuff - by Jack's Magic". This is intended to remove the remaining copper from the water which is within acceptable levels but still high. I don't know how well this stuff works but I'll take a water test before and then after to see how well it clears up the copper.
    Dan Cormack
    Pool: 19,000 Gal, IG, Vinyl, Sand Filter (installed 2007), Pentair Model 320 Automatic Chlorine In-Line feeder
    Test Kit: Taylor K-2006

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    JoyfulNoise's Avatar
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    Purple Precipitate

    Jacks Blue Stuff doesn't "remove" copper from the water, it sequesters the metal ion which is to say it forces the copper ion to stay in solution. Sequestrants will break down over time from exposure to UV light and chlorine. As the sequestrant breaks down, copper ions become less soluble and can form stains (scale) again.

    The only way to completely remove metals from pool water is to redisolve the stains, add sequestrant to hold the ion in solution and then dump the pool water and refill with fresh water.
    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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    May 2017
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    Re: Purple Precipitate

    Quote Originally Posted by JoyfulNoise View Post
    Jacks Blue Stuff doesn't "remove" copper from the water, it sequesters the metal ion which is to say it forces the copper ion to stay in solution. Sequestrants will break down over time from exposure to UV light and chlorine. As the sequestrant breaks down, copper ions become less soluble and can form stains (scale) again.

    The only way to completely remove metals from pool water is to redisolve the stains, add sequestrant to hold the ion in solution and then dump the pool water and refill with fresh water.
    Thank you for that advice! This is exactly what I am working on doing at the moment. I am draining and filling pool water to reduce the CYA and Cu levels. It's a slow process obviously. I have stopped using the 3" tablets in favor of liquid chlorine until this is all resolved.
    Dan Cormack
    Pool: 19,000 Gal, IG, Vinyl, Sand Filter (installed 2007), Pentair Model 320 Automatic Chlorine In-Line feeder
    Test Kit: Taylor K-2006

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