Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 6 of 6

Thread: Blue Stains on Plaster Surface

  1. Back To Top    #1

    Join Date
    Mar 2016
    Location
    Medford, Oregon
    Posts
    160

    Blue Stains on Plaster Surface

    Having drained our in-ground gunite, saltwater spa for a pressure test, I noticed that the white plaster has faded bluish stains on all the surfaces. What might be the cause? Can it be easily removed now that the spa is empty? BTW, the spa is about 6 months old.

    Thank you.
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

  2. Back To Top    #2
    Mod Squad YippeeSkippy's Avatar
    Join Date
    Jan 2012
    Location
    'burbs of Augusta, Georgia
    Posts
    6,262

    Re: Blue Stains on Plaster Surface

    Do you add any copper containing algaecides or have a mineral system for sanitation?
    Maddie 12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
    Our pool build--> Our Pool Solved Our Sloping Yard Skippy's Cheap Pool Cooler -->Skippy's New Fountain

  3. Back To Top    #3

    Join Date
    Mar 2016
    Location
    Medford, Oregon
    Posts
    160

    Re: Blue Stains on Plaster Surface

    Quote Originally Posted by YippeeSkippy View Post
    Do you add any copper containing algaecides or have a mineral system for sanitation?
    No. I might add that the chemistry has always been in balance. However, I am experiencing a possible salt level issue & might have been guilty of adding too much additional salt. Might that be a factor? Thank you.
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

  4. Back To Top    #4
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    Location
    DFW, TX
    Posts
    23,833

    Re: Blue Stains on Plaster Surface

    The two most likely causes are calcium scaling or copper stains. Is the surface of the stain raised and rough? Do you have some test results? Both can be removed with dry acid in a sock or spraying muriatic acid on it and brushing.

    Common sources of copper are
    Mineral systems
    Ionizers
    Other "natural" sanitizers
    Pucks or shock labeled "blue"
    Algaecides
    Eroded copper heater from pH below 7.0

    More about scale here, Pool School - Calcium Scaling
    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

  5. Back To Top    #5

    Join Date
    Mar 2016
    Location
    Medford, Oregon
    Posts
    160

    Re: Blue Stains on Plaster Surface

    Quote Originally Posted by pooldv View Post
    The two most likely causes are calcium scaling or copper stains. Is the surface of the stain raised and rough? Do you have some test results? Both can be removed with dry acid in a sock or spraying muriatic acid on it and brushing.

    Common sources of copper are
    Mineral systems
    Ionizers
    Other "natural" sanitizers
    Pucks or shock labeled "blue"
    Algaecides
    Eroded copper heater from pH below 7.0

    More about scale here, Pool School - Calcium Scaling
    No, this is not what I would consider as scaling. The surface is neither raised nor rough. It is not along the waterline on the tile. It is only on the white plaster surface. The plaster is smooth. There is just a spotty, bluish tinge in the plaster. I assume that it is not copper staining since none of the sources you listed would apply to my spa. BTW, I used a nylon brush with a 3:1 ratio of water/acid to see if I could remove the blue. No luck.

    I would like to identify the cause so I can (1) remove the spotty blue discoloration if possible & (2) avoid the problem in the future. Some typical test results are as follows:

    FC = 5
    pH = 7.8 (target = 7.6)
    CH = 350
    TA = 90 (target = 80)
    CYA = 60 (target = 70 - 80)
    CC = 0.0

    Thank you for your help.
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

  6. Back To Top    #6

    Join Date
    Mar 2016
    Location
    Medford, Oregon
    Posts
    160

    Re: Blue Stains on Plaster Surface

    I am thinking that this blueish tinge might simply be a reaction to the various pool chemicals. Does this make sense?
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •