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Thread: What is this?

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    meatloaf's Avatar
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    What is this?

    I have some strange raised bumps on the bottom of my plaster pool. They range in size from a dime to 1/2 dollar. They can be scrapped off using a pumice stone. What could have caused these and what is the best way to remove them? Thanks
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    My pool is a 10,500 gallon (420 Sq Ft ) kidney shape. A hand made sheer decent waterfeature. STA-RITE HRPB30, Sand filter 30" 98 GPM,
    1 HP Maxi-Glas 2 pump, BBB Method, Taylor K-2005 test kit, 50 Watt 12V low-voltage pond light illuminates the pool at night for a nice soft glow.
    250 gallon stand-alone hot tub. Got it FREE!

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    frustratedpoolmom's Avatar
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    Re: What is this?

    Kinda look like Black Algae, but its hard to tell from the pics.
    try rubbing a trichlor tablet on a spot, see what it does.
    When you use the pumice stone - does it leave behind any residual or staining?
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

  3. Back To Top    #3
    meatloaf's Avatar
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    Re: What is this?

    I'll try the chlorine tablet and see what happens. When I used the pumice stone, the spots get small but you can still see a small mark.
    My pool is a 10,500 gallon (420 Sq Ft ) kidney shape. A hand made sheer decent waterfeature. STA-RITE HRPB30, Sand filter 30" 98 GPM,
    1 HP Maxi-Glas 2 pump, BBB Method, Taylor K-2005 test kit, 50 Watt 12V low-voltage pond light illuminates the pool at night for a nice soft glow.
    250 gallon stand-alone hot tub. Got it FREE!

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    frustratedpoolmom's Avatar
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    Re: What is this?

    try the tablet on the spots left behind after the pumice stone. Black algae has these roots, the heads are resistant to chlorine but once you "knock off the heads" the chlorine can attack the roots.

    It is possible that's what's happening here - how often are you running your pump/filter- and what chem levels are you maintaining? IF you could post a full set of results that would help us advise better.

    Black Algae can get started and survive in 'normal' levels of chlorine if circulation is poor - what can happen is these FC dead spots - if there isn't adequate circulation time... esp during the daytime hours when the sun is attacking your chlorine. Do you run the pump during the day at all?
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Re: What is this?

    Quote Originally Posted by frustratedpoolmom
    Kinda look like Black Algae, but its hard to tell from the pics.
    try rubbing a trichlor tablet on a spot, see what it does.
    When you use the pumice stone - does it leave behind any residual or staining?
    Ann, sorry to say that that looks nothing like Black algae

    It does look like some sort of algae clump.

    Nail it with cl and I'd bet it just goes 'bye bye'
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    Butterfly's Avatar
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    Re: What is this?

    meatloaf, what CYA and FC levels do your normally maintain?

    Do you have test results to post?
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

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    frustratedpoolmom's Avatar
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    Re: What is this?

    Quote Originally Posted by waste
    Quote Originally Posted by frustratedpoolmom
    Kinda look like Black Algae, but its hard to tell from the pics.
    try rubbing a trichlor tablet on a spot, see what it does.
    When you use the pumice stone - does it leave behind any residual or staining?
    Ann, sorry to say that that looks nothing like Black algae

    It does look like some sort of algae clump.

    Nail it with cl and I'd bet it just goes 'bye bye'
    Looks like BA pics I've seen...
    plus he said he had to remove it with a pumice stone and it left a residual stain. That 'sounds' like black algae from the description.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    meatloaf's Avatar
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    Re: What is this?

    Test results are,
    CL 3
    PH 7.5
    TA 90
    CH 550
    CYA 45 (APPROX)

    I scraped one spot this morning and set a puck over the remaining spot, there is little to no change and the puck sat there for 8 hours.
    Thanks
    My pool is a 10,500 gallon (420 Sq Ft ) kidney shape. A hand made sheer decent waterfeature. STA-RITE HRPB30, Sand filter 30" 98 GPM,
    1 HP Maxi-Glas 2 pump, BBB Method, Taylor K-2005 test kit, 50 Watt 12V low-voltage pond light illuminates the pool at night for a nice soft glow.
    250 gallon stand-alone hot tub. Got it FREE!

  9. Back To Top    #9
    frustratedpoolmom's Avatar
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    Re: What is this?

    Well, if the spots were organic then the tablet would have done something I would think.
    I'm stumped. Maybe Ted has a suggestion.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Butterfly's Avatar
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    Re: What is this?

    Has your pH been above 7.8?...or has it lingered around 7.8?
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  11. Back To Top    #11
    meatloaf's Avatar
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    Re: What is this?

    PH did get to 7.8, but only for a day or two.
    My pool is a 10,500 gallon (420 Sq Ft ) kidney shape. A hand made sheer decent waterfeature. STA-RITE HRPB30, Sand filter 30" 98 GPM,
    1 HP Maxi-Glas 2 pump, BBB Method, Taylor K-2005 test kit, 50 Watt 12V low-voltage pond light illuminates the pool at night for a nice soft glow.
    250 gallon stand-alone hot tub. Got it FREE!

  12. Back To Top    #12
    Butterfly's Avatar
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    Re: What is this?

    High pH + high CH = calcium deposits. Maybe running the ph lower, around 7.2 for a week or so and brushing could clear the problem. See what others think on this.

    Also, someone out your way (can't remember who) runs a low Chlorine to CYA ratio - keeps it teetering at or around the minimum. This would create an enviornment for a all kinds of algae, even black.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  13. Back To Top    #13
    meatloaf's Avatar
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    Re: What is this?

    I think I figured out the problem. Calcium deposits, they seem to scrape off with little or no residue. I'm going to try to keep the PH @ 7.4 or below for a while and see if that helps.
    New numbers are:
    CL-3
    PH-7.4
    TA-90
    CH-590
    CYA-50
    TEMP-82*
    My pool is a 10,500 gallon (420 Sq Ft ) kidney shape. A hand made sheer decent waterfeature. STA-RITE HRPB30, Sand filter 30" 98 GPM,
    1 HP Maxi-Glas 2 pump, BBB Method, Taylor K-2005 test kit, 50 Watt 12V low-voltage pond light illuminates the pool at night for a nice soft glow.
    250 gallon stand-alone hot tub. Got it FREE!

  14. Back To Top    #14
    BobinBaltimore's Avatar
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    Re: What is this?

    It may be worth trying a de-scaling product to see if there is some improvement. Your CH may be the culprit (or a big contributor). Is your tap or well water hard?
    25' x 37' freeform, 22,000 gallon saltwater, 3'6" to 6'6" deep, including baja shelf and benches, 120 ft EP Henry retaining wall
    Pentair equipment (CC420 cartridge filter, VS-3050 variable speed pump, IC 60 salt cell, EasyTouch), 200 sq ft pool house
    View our Pool Build - View our Pool House Build

  15. Back To Top    #15
    meatloaf's Avatar
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    Re: What is this?

    Tap / Fill water tests @ 250. I've been here for 5 years and the pool has never been totally drained, just partial draining to lower CYA. I think during the winter would be a great time for a complete drain, acid wash & refill.
    I did purchase a bottle of BioGaurd scale inhibitor and added that yesterday.
    My pool is a 10,500 gallon (420 Sq Ft ) kidney shape. A hand made sheer decent waterfeature. STA-RITE HRPB30, Sand filter 30" 98 GPM,
    1 HP Maxi-Glas 2 pump, BBB Method, Taylor K-2005 test kit, 50 Watt 12V low-voltage pond light illuminates the pool at night for a nice soft glow.
    250 gallon stand-alone hot tub. Got it FREE!

  16. Back To Top    #16
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    Re: What is this?

    With your fill water that high, and the evaporation rates that you see, your CH will build again quickly. Have you considered R/O (Reverse Osmosis)? There is a good company out near you that I might be able to recommend, if you wish.

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