Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 3 of 3

Thread: Brown stains and dry acid

  1. Back To Top    #1

    Join Date
    Feb 2016
    Location
    Brisbane, Australia
    Posts
    11

    Brown stains and dry acid

    I've noticed brown stains in the pool recently. I found this post (Brown stains not from iron) which recommends vitamin C tabs as one of the tests.

    I assumed I need something acidic, so I use dry acid (the stuff I use to lower pH levels). Placed a bit in a sock and "painted" the pool wall, and the brown came off quite easily (only a tiny bit of pressure required)

    Was it ok to use dry acid as a substitute for vitamin C tabs?

    Could this be an iron stain? (they are all over the pool, bar a couple of spots).
    Pool size: ~50,000L vinyl, Pump: ???, SWG: AutoChlor RP25T
    Filter: Sand, Test kit: Taylor K-2006 (FAS-DPD)

  2. Back To Top    #2
    JoyfulNoise's Avatar
    Join Date
    May 2015
    Location
    Tucson, AZ
    Posts
    11,580

    Re: Brown stains and dry acid

    Dry acid is mostly sodium bisulfate which can form very strongly acidic solutions. It will definitely remove metal stains but it can also be quite corrosive to plaster. Ascorbic acid, on the hand, is less acidic but very good at removing iron stains because it is also a chelating agent. AA is the preferred way to perform the test for metal stains as it is non-destructive to plaster.

    That said, it sounds like you have metal stains and that an AA treatment will help.


    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

  3. Back To Top    #3

    Join Date
    Feb 2016
    Location
    Brisbane, Australia
    Posts
    11

    Re: Brown stains and dry acid

    Quote Originally Posted by JoyfulNoise View Post
    Dry acid is mostly sodium bisulfate which can form very strongly acidic solutions. It will definitely remove metal stains but it can also be quite corrosive to plaster. Ascorbic acid, on the hand, is less acidic but very good at removing iron stains because it is also a chelating agent. AA is the preferred way to perform the test for metal stains as it is non-destructive to plaster.

    That said, it sounds like you have metal stains and that an AA treatment will help.


    Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
    Thanks Joyful.

    Note to self: don't use dry acid for testing like that again My pool in vinyl so I hope i'm ok! (only a small area tested anyway)
    Pool size: ~50,000L vinyl, Pump: ???, SWG: AutoChlor RP25T
    Filter: Sand, Test kit: Taylor K-2006 (FAS-DPD)

Posting Permissions

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