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Thread: discolouration around waterline

  1. Back To Top    #1

    Join Date
    May 2016
    Location
    Hobart, Tasmania, Australia
    Posts
    13

    discolouration around waterline

    Hi.

    I've recently become the owner of a 1,800 gal, 3 y.o. swimspa with I believe an acrylic surface. Around and above the waterline, the surface has a whitish colour to it. Not a thick rough/textured layer deposited on the surface, just a super thin layer that appears more as a whitish discolouration.

    As a background on the pool, when I moved in to the house the pools's water parameters were:


    FC - over 100
    CC - 0
    pH - approx 8.2 (couldn't really tell with high FC, but after bringing FC down and reducing TA it's still a bit high)
    CH - 110
    TA - 170
    CYA ~0
    Temp 36C/97F

    After a bit of work, it's currently at:
    FC - 4
    CC - 0.5
    CH - 110
    TA - 145
    CYA - about to add some, I decided to get FC under control and the SWG tuned in a bit first.

    I know chlorine can bleach some surfaces, but will it do this to acrylic? And I haven't noticed it below the water where it was constantly exposed, only above. However as it isn't real bad the water may tend to hide the effect.

    Is it likely to be from the chlorine? Or could it be calcium carbonate deposited on the surface? CSI when I moved in would calculate out to 0.5 (assuming pH 8.2) which is a little high but not excessive.

    What is the best way to try to clean it? Dilute acid? What strength? Or something else?

    Thanks in advance,
    Brett
    1,800g AG Endless Swim Spa, Cartridge Filter, Davey Pumps, Davey Ecosalt MES13AMP SWG
    6kW electric heater. Installed 2013, I became owner May 2016

  2. Back To Top    #2
    Mod Squad pooldv's Avatar
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    Re: discolouration around waterline

    Yes, it is a little calcium scale build up. I had the same a few years ago. I lowered CSI to 0 to -0.3 and it's been gone ever since. I just brushed it some while I was in the pool with a hand brush. You could use some acid, maybe 4 to 1 dilution. Always add acid to water and never water to acid.
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    Mod Squad tim5055's Avatar
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    Re: discolouration around waterline

    It's minerals left behind when water evaporates just above the water line. I clean it with straight muratic acid when it bothers me and my pH needs a bump down. I use one of these: Amazon.com : Purity Pool OS Out Spot Stain Remover : Swimming Pool Stain Removers : Patio, Lawn Garden

    You load the tube with acid and just gently slide it over the stains. It is not a scrub brush, just an acid delivery tool.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

  4. Back To Top    #4

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    May 2016
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    Hobart, Tasmania, Australia
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    Re: discolouration around waterline

    Thanks guys.

    I've been using muriatic acid to lower my pH/TA. I've been adding it to a bucket of pool water, then slowly pouring this in the swimjet stream to thoroughly mix it in the pool, bringing the overall pH down to 7.3 (until the aeration raises it).

    I'll try brushing around the waterline with some of the diluted acid in the bucked. I wanted to make sure my thoughts were heading in the right direction before I did something I regretted later! I didn't want to damage the pool surface.
    1,800g AG Endless Swim Spa, Cartridge Filter, Davey Pumps, Davey Ecosalt MES13AMP SWG
    6kW electric heater. Installed 2013, I became owner May 2016

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    Mod Squad tim5055's Avatar
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    Re: discolouration around waterline

    Ah, I just noticed you are down under... I guess Amazon is not a good choice.

    I guess I'm jus tnot a fan of diluting acid in a bucket before pouring it in the pool. Just another step where acid can splash.

    Some folks do put dilute acid in a spray bottle and use a scrub pad with the spray acid to remove the water line scale. Always remember, use PPE - Personal Protective Equipment when using acid, especially safety glasses/goggles.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

  6. Back To Top    #6

    Join Date
    May 2016
    Location
    Hobart, Tasmania, Australia
    Posts
    13

    Re: discolouration around waterline

    With my size pool, and current alkalinity, I only need to add about 180ml (6 fl OZ I think?) of acid to drop the pH. I prefer to suck out two syringes of acid from the container in the pool shed (has a long tube attachment) and put that straight into half a bucket of poolwater. That way I'm only carrying it around diluted rather than carrying two syringes or a separate container with the measured acid and adding it to my AG pool at chest height.

    Different people have different pools, circumstances and preferences though - whatever works best for your situation, as long as it's done safely
    1,800g AG Endless Swim Spa, Cartridge Filter, Davey Pumps, Davey Ecosalt MES13AMP SWG
    6kW electric heater. Installed 2013, I became owner May 2016

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