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Thread: What are these rust spots from, and how do I get rid of them?

  1. Back To Top    #1

    Join Date
    Jul 2015
    Location
    Las Vegas, NV
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    What are these rust spots from, and how do I get rid of them?

    Hello, long time reader, but first post! I have read through the pool school articles, and they're great!

    We bought our house in September of last year. The pool was built in 09, the house 06. So far, we've really enjoyed having a pool, especially in the Las Vegas summer! It has been fairly easy to maintain, and they used higher end (at the time) components with the install.

    Since we've been here, I have noticed a few small dark red/brown spots around the pool, but they were extremely small. Lately though, they are getting much more prevalent, so I'm getting concerned! The spots are ONLY on the bottom surfaces, including the stairs. They are not on the sides. Here are a few pictures so we're all on the same page here...

    The pool in question-

    Around 12k gallons
    Plaster
    No heater
    Chlorine tabs
    Pentair variable speed pump
    Pentair clean and clear filter
    Drained and refilled about 3 months ago




    Some of the spots I'm talking about-



    Some areas aren't as bad as others. Most of the dark spots in the picture are the rust specks though,as there are no dark colors in the plaster.



    So I have been to both NPS and Leslie's in the past few days, and they have both tested my water with good results (yes, I test it too). I have showed them pictures, and neither knows the cause. I have tried holding a chlorine tablet on them to see if they're organic, and they don't go away or lighten. Then I tried a Vitamin C pill. It didn't really do anything to the spot itself.... instead it made the area right around the spot redish. (don't worry, that red slowly faded away) See the pic below...



    I purchased a bottle of Biodex Stain Off, added the entire bottle, and absolutely no change.


    So, I'm puzzled as to where these spots are coming from, but more importantly, how I can get rid of them.

    Please help!! Thanks in advance...

  2. Back To Top    #2

    Join Date
    Jun 2015
    Location
    Raleigh
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    Re: What are these rust spots from, and how do I get rid of them?

    If you're testing it too what are your numbers? What's your CH?
    18' x 38' Pool, 3' to 8' Depth
    Vinyl Liner
    SWG
    Variable Speed Pump
    Sand Filter

  3. Back To Top    #3

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    Jul 2015
    Location
    Las Vegas, NV
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    Re: What are these rust spots from, and how do I get rid of them?

    Quote Originally Posted by robertmee View Post
    If you're testing it too what are your numbers? What's your CH?
    Hey there, thanks for the reply!

    Total Chlorine 3.0
    pH 7.4
    Alkalinity 110
    CH 400

    Pool store result of TDS-
    1100
    Las Vegas, NV
    12,000 plaster built in 09
    Pentair variable speed
    Pentair Clean and Clear cartridge
    TF100

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    PoolESQ's Avatar
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    Dec 2007
    Location
    Albuquerque, NM
    Posts
    191

    Re: What are these rust spots from, and how do I get rid of them?

    You will also need to test your CYA level and post it to get the most accurate answers here. As you begin to read the form, you will learn they have developed a FC:CYA ratio table; that is, if your CYA = X, then your FC should be Y. The table obviously uses real number in place of X and Y. There is no way of knowing whether a CL level of 3.0 is good or low without the CYA figure as well.
    Replastered 2015: Sunstone Quartz Midnight Blue 16x32 rectangular gunite with in-pool spa....18,000 gallons. Autopilot Total Control System with SWG and acid pump. Pentair Clean & Clear 420. Auto cover. TF-100.

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    Re: What are these rust spots from, and how do I get rid of them?

    Crush up some cheap vitamin C tablets, put them in an old sock and weigh the sock down so it is in direct contact with the stains. Leave it on for about 5 minutes or so.

    Remove the sock and observe if the stain is gone or, at least, very noticeably improved.

    If so, it's iron staining. Post back if that works.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: What are these rust spots from, and how do I get rid of them?

    Quote Originally Posted by duraleigh View Post
    Crush up some cheap vitamin C tablets, put them in an old sock and weigh the sock down so it is in direct contact with the stains. Leave it on for about 5 minutes or so.

    Remove the sock and observe if the stain is gone or, at least, very noticeably improved.

    If so, it's iron staining. Post back if that works.
    I think he already tried this, although it's not clear the method of application he used:

    "Then I tried a Vitamin C pill. It didn't really do anything to the spot itself.... instead it made the area right around the spot redish. (don't worry, that red slowly faded away) See the pic below..."
    18' x 38' Pool, 3' to 8' Depth
    Vinyl Liner
    SWG
    Variable Speed Pump
    Sand Filter

  7. Back To Top    #7

    Join Date
    Jul 2015
    Location
    Las Vegas, NV
    Posts
    13

    Re: What are these rust spots from, and how do I get rid of them?

    Quote Originally Posted by robertmee View Post
    I think he already tried this, although it's not clear the method of application he used:

    "Then I tried a Vitamin C pill. It didn't really do anything to the spot itself.... instead it made the area right around the spot redish. (don't worry, that red slowly faded away) See the pic below..."
    Yep, even bought a bottle of ascorbic acid and poured a little on my top step. Let it sit for 30 mins, and it didn't even touch the stains.
    Las Vegas, NV
    12,000 plaster built in 09
    Pentair variable speed
    Pentair Clean and Clear cartridge
    TF100

  8. Back To Top    #8

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    Sebring, Florida
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    Re: What are these rust spots from, and how do I get rid of them?

    Either the tabs or the vitamin c tests should work.

    If they don't, then your stain is neither organic or inorganic.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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