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Thread: Chlorine powder black stains

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    Join Date
    Jun 2013
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    Chlorine powder black stains

    My pool cleaner inadvertently left the discharge valve open causing a 30% loss of water before being noticed.The pool was filled from our well supply and the once sparkling blue water in the pool was now a very light teal colour.I shocked the pool with powdered chlorine and the undissolved powder has badly stained the ceramic tiles on the base of the pool.No amount of scrubbing with the pool brush will remove the black stains.What are my options?I really don't want to drain a 60,000 litre pool.

    THX Steve
    20,000 gallons,sand filter,IG,ceramic tiles,Hayward super pump

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    duraleigh's Avatar
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    Re: Chlorine powder black stains

    Welcome to the forum. I don't think you have many options other than to just keep your pool chlorinated and hope it diminishes over time.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Isaac-1's Avatar
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    Re: Chlorine powder black stains

    Do you know what type of powdered chlorine product you used? Without know a lot more details this is a bit of a wild guess, but the spots you have may be metal stains, try rubbing a common vitamin C tablet available at most health stores on one of the tiles and see if it lifts the stains.

    Ike
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
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    Re: Chlorine powder black stains

    It's most likely copper stains. This is usually happens when the pH and TA are too low. Try some baking soda on the stain. Add some sequestrant when you get a chance.

    What were all of your readings at the time you added the shock?

    I'm not sure if low ph and ta are related to the cases that I know of or if it's just coincidental. Also the cases that I know of have all involved cal hypo contacting the surface.

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    Re: Chlorine powder black stains

    Thanks guys for your prompt replies.Ike I haven't been able to get in touch with the chemical supplier but will tomorrow and let you know.James my pH was 6.8 and TA 50 before shocking.24hrs after shocking pH was >than8.2 and TA 100.The present update to this is I added HCL to lower the pH and knowing that acid is heavier than water,I poured it into the pool directly above one of the larger stains.As if by magic the stain disappeared.I use two stabilized chlorine tablets in this pool and they keep the chlorine level stable at3.0.I noticed that if I slide one of these over the stain,they also remove the stain but not as rapid.So its good news as I won't have to drain the pool,just devise a means of wiping the stains with the acid under water.This has removed a huge weight of my shoulders as a clean and bright pool equates to a happy household.


    regards Steve
    20,000 gallons,sand filter,IG,ceramic tiles,Hayward super pump

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    Re: Chlorine powder black stains

    See some products from Purity Pool that can be used to apply acid or other chemicals (such as ascorbic acid for metal stain removal) easily. In your case, it sounds like some acid will do the trick.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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