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Thread: White chalky residue on fiberglass pool

  1. #1
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    White chalky residue on fiberglass pool

    I did a search for this problem on TPF with no results so:
    My sister in law and I have fiberglass pools with a chalky film on the sides, below the water level. It wipes off easily and clouds the water with swimmers stiring it up. Hers is worse than mine and the pools are about 8 yrs old.
    Readings are similar.

    fc 6
    cc 0
    tc 6
    ph 7.4
    ta 150
    ch 150
    cya 50

    Is the glass getting old and chalking like boats do?
    Any ideas on cause and fix?
    We also have a few small black stains that look like they fan out from the center in one direction. About pencil eraser size.
    15,000 gal Sun Fiberglass, Glass/Lexan/Aluminum Enclosed Room, 1.5 hp Pentair Whisperflow Pump, Triton 100- 600# Sand Filter, Heat Siphon Heat Pump, 3 Dbl. Seats w/8 Jets, Waterfall, 8' Interfab Slide, Pentair SAm Spectrum Amerlite Pool Light, Stenner MHP5 Chlorine Pump, Kreepy Krauly Vacuum, Bleach, 50 ppm Borates, TF 100 Test Kit

  2. #2
    Senior Member dremin2flyhi's Avatar
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    Re: White chalky residue on fiberglass pool

    my uncle had this problem when he used Calcium based shock / chlorine products--after switching to a SWG --this problem has since gone away. Not sure what products you are using there but that would be one of the first things to check.
    24' x52" ABG (13,500)
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    Duraspa G2- Premium hot tub --Rotomold style

  3. #3
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    Re: White chalky residue on fiberglass pool

    Thanks. I use bleach but did use cal hypo until 2 years ago. I just converted her to bleach last winter. Our ch #s are fairly low so ???
    15,000 gal Sun Fiberglass, Glass/Lexan/Aluminum Enclosed Room, 1.5 hp Pentair Whisperflow Pump, Triton 100- 600# Sand Filter, Heat Siphon Heat Pump, 3 Dbl. Seats w/8 Jets, Waterfall, 8' Interfab Slide, Pentair SAm Spectrum Amerlite Pool Light, Stenner MHP5 Chlorine Pump, Kreepy Krauly Vacuum, Bleach, 50 ppm Borates, TF 100 Test Kit

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    Re: White chalky residue on fiberglass pool

    That's a puzzle. When you hear "white, chalky" Calcium is about the only thing that comes to mind. There is nothing in your test results to support that, however, and calcium usually attaches hard when it precipitates.

    Are you both using some other additive into your pool for ANY reason?
    Dave S.
    Site Owner 42k vinyl and concrete pool, 1.5hp pump, 140gpm filter, No SWG
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    Re: White chalky residue on fiberglass pool

    The only thing I use is 6% bleach, muratic acid (not much) and on occasion a clarifier/coagulant called "Super Blue". I use citric acid for tan stains I get but sis has never used it and her chalkyness is worse. She had clarity issues all last year depending on "pool places" to help her. Finally, last fall she came to me and I had her pool crystal clear in 4 days and has been good since. My pool is indoors w/clear lexan panel roof and hers is outdoors. We both have sand filters and we're both on well water. We're using hers today so I told her to add the Super Blue while the pool is stirred to see how much the filter will remove. I use duraleigh's testing supplies and the aireation method to raise ph after citric application. We'll see what happens.
    Thanks for your input.
    15,000 gal Sun Fiberglass, Glass/Lexan/Aluminum Enclosed Room, 1.5 hp Pentair Whisperflow Pump, Triton 100- 600# Sand Filter, Heat Siphon Heat Pump, 3 Dbl. Seats w/8 Jets, Waterfall, 8' Interfab Slide, Pentair SAm Spectrum Amerlite Pool Light, Stenner MHP5 Chlorine Pump, Kreepy Krauly Vacuum, Bleach, 50 ppm Borates, TF 100 Test Kit

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    Mod Squad Bama Rambler's Avatar
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    Re: White chalky residue on fiberglass pool

    Are both pools about the same age?
    Dave J. TFP Moderator
    24' x 52" Round AGP. 1.5hp Dynamo pump. 24" Pentair Sand Dollar Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit
    You can stop SLAMing your pool when you pass the OCLT (You lose 1ppm or less FC overnight, & You have .5ppm CC's or less) & your water is clear.

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    Re: White chalky residue on fiberglass pool

    Yes, about the same age. Looks like chalk you see on fiberglass boats.
    15,000 gal Sun Fiberglass, Glass/Lexan/Aluminum Enclosed Room, 1.5 hp Pentair Whisperflow Pump, Triton 100- 600# Sand Filter, Heat Siphon Heat Pump, 3 Dbl. Seats w/8 Jets, Waterfall, 8' Interfab Slide, Pentair SAm Spectrum Amerlite Pool Light, Stenner MHP5 Chlorine Pump, Kreepy Krauly Vacuum, Bleach, 50 ppm Borates, TF 100 Test Kit

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    Mod Squad Bama Rambler's Avatar
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    Re: White chalky residue on fiberglass pool

    Sounds like a problem with the gel coat. Since they're both the same brand and age I'd contact the mfg and see what they say about it.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 1.5hp Dynamo pump. 24" Pentair Sand Dollar Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit
    You can stop SLAMing your pool when you pass the OCLT (You lose 1ppm or less FC overnight, & You have .5ppm CC's or less) & your water is clear.

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    Re: White chalky residue on fiberglass pool

    Here's the manufacturers chem. bal. recommendations. LOL My pool would be a slime ball at fc 1 ppm. I'm sure they're going to say my chlorine is too high and damaged the finish but I'll wait and see. I'll post their reply.
    Thanks again.


    CARE AND MAINTENANCE MANUAL

    FOR SUN FIBERGLASS POOLS


    RECOMMENDED RANGES FOR DESIRED WATER BALANCE

    CHLORINE 1.0 ppm
    P.H. 7.4 to 7.6
    TOTAL ALKALINITY 80 ppm to 100 ppm
    CALCIUM HARDNESS 350 ppm
    STABILIZER CYANURIC (conditioner) 60 ppm
    15,000 gal Sun Fiberglass, Glass/Lexan/Aluminum Enclosed Room, 1.5 hp Pentair Whisperflow Pump, Triton 100- 600# Sand Filter, Heat Siphon Heat Pump, 3 Dbl. Seats w/8 Jets, Waterfall, 8' Interfab Slide, Pentair SAm Spectrum Amerlite Pool Light, Stenner MHP5 Chlorine Pump, Kreepy Krauly Vacuum, Bleach, 50 ppm Borates, TF 100 Test Kit

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    Re: White chalky residue on fiberglass pool

    My pool manufacturer replied and here's his response:

    Hello,
    Based on your description it sounds like a scale/mineral buildup. I have had good success using a product called Scale Tec Plus to
    remove the build up. It will take two to four weeks for noticeable change, but left un treated the scale could harden and be come
    very hard to remove. Here is a link for the product: http://www.mcgrayel.com/scaletecplus.html
    I do see from your chemical list that the Free CL is high 5ppm is very high. We recommend a range of 1-3 ppm. Also using Liquid
    Chlorine will cause gel coat damage over time. The use of a Cal-Hypo or other granular shock is recommended. The Calcium
    hardness should be 250-350. We recommend the higher side of that. Although until you get the scale down I would not add
    extra chemicals. I understand that running a heated pool requires more chlorine at 85 degrees but still need to keep it down closer to 1-3 range. Let me know if you have any other questions. During the scale treatment extra brushing will help to speed the process along a little.

    Then I talked to the only local pool dealer I half way trust and he said to get my CH above 200 and the chalkyness will go away. He said the low calcium level causes fiberglass pools to oxidize which is what I'm seeing. He was quick with the answer and said he's seen it before.
    I think I'll try raising the calcium first. It sounds good to me.
    15,000 gal Sun Fiberglass, Glass/Lexan/Aluminum Enclosed Room, 1.5 hp Pentair Whisperflow Pump, Triton 100- 600# Sand Filter, Heat Siphon Heat Pump, 3 Dbl. Seats w/8 Jets, Waterfall, 8' Interfab Slide, Pentair SAm Spectrum Amerlite Pool Light, Stenner MHP5 Chlorine Pump, Kreepy Krauly Vacuum, Bleach, 50 ppm Borates, TF 100 Test Kit

  11. #11

    Re: White chalky residue on fiberglass pool

    I have the same problem and have tried everything. Has anyone come up with a solution or figured out what is causing this ? I pray that it is not a gelcoat problem. My pool is 4 years old now but I started having this problem after about a year. Started with a salt gen. system, switched over to see if this would make a difference. Drained the pool, completely changed the sand in the filter and scrubbed the pool walls until I could not remove any more of the chalky residue. Filled it back up, balanced it and it came back in a few months. Me and everyone I have talked to or worked with is stumped. HELP!

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    Re: White chalky residue on fiberglass pool

    John,

    Welcome to TFP!

    Were you keeping the Calcium Hardness (CH) and other water parameters at levels to have the saturation index near 0 (sometimes called LSI or CSI)? Just trying to get another data point as to what might be the cause.
    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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    Re: White chalky residue on fiberglass pool

    I have also been experiencing this issue with my 3 year old fiberglass pool. Can anyone tell if any of these methods worked?
    23k gal, vinyl, 1 HP Centurion, Sta-Rite sand filter, MS-10 with T-15 cell

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    Re: White chalky residue on fiberglass pool

    I know this is an old subject but here's what I did: My pool manufacturer thinks it's the beginning of scaling. They and my local pool guy said to get the CH up to 300-350. Manufacturer suggested I use a stain/scale treatment called Scaletec. I couldn't find it locally so I used Aqua Chem scale metal and stain control as directed except added weekly instead of monthly maint. doses and raised CH to 300. After a few weeks of brushing my chalkyness is gone.
    15,000 gal Sun Fiberglass, Glass/Lexan/Aluminum Enclosed Room, 1.5 hp Pentair Whisperflow Pump, Triton 100- 600# Sand Filter, Heat Siphon Heat Pump, 3 Dbl. Seats w/8 Jets, Waterfall, 8' Interfab Slide, Pentair SAm Spectrum Amerlite Pool Light, Stenner MHP5 Chlorine Pump, Kreepy Krauly Vacuum, Bleach, 50 ppm Borates, TF 100 Test Kit

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    Re: White chalky residue on fiberglass pool

    Hey Capt thanks for the report back. I'm sure this will help others.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 1.5hp Dynamo pump. 24" Pentair Sand Dollar Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit
    You can stop SLAMing your pool when you pass the OCLT (You lose 1ppm or less FC overnight, & You have .5ppm CC's or less) & your water is clear.

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    Re: White chalky residue on fiberglass pool

    Just bumping up this thread and thanking for the great advice contained within it. I've fought this problem for years. I've been around to every pool store and they are all stumped by it. I've heard a variety of reasons why this was happening. Most folks will tell a fiberglass pool owner not to worry about CH. It just happened to me yesterday at a pool store who refused to sell me hardness plus because #1 - they haven't tested my water and argue that my tests at home are inaccurate (I'm using the TF-100 kit) #2 - There's no way my water can be that "soft" (it is!) and #3 - I don't need to worry about it.

    We're in the process of draining and refilling in preparation for a new SWG (which requires a lot lower salt content than it's predecessor). Once we add the new water and I've tested, I'll finally be able to (hopefully) conquer this problem. I'll report back.
    Central Indiana, 7200 gallon, IG fiberglass, L250 Jacuzzi sand filter, Hayward H150 gas heater, Pentair fiber optic light - installed '06. AOSmith 1.0hp pump, CPSC-24 SWG - installed '13. TF-100 Test Kit.

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    Re: White chalky residue on fiberglass pool

    After I posted my above message and walked away, a question popped into my head:

    Since I've drained about 2/3rds of my water to remove salt AND to caulk the jets and light........

    Could I use that Scaletec to scrub the sides and keep draining out water? That way I could hurry this along rather than waiting for it to work over time? (I hope that makes sense)
    Central Indiana, 7200 gallon, IG fiberglass, L250 Jacuzzi sand filter, Hayward H150 gas heater, Pentair fiber optic light - installed '06. AOSmith 1.0hp pump, CPSC-24 SWG - installed '13. TF-100 Test Kit.

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    Re: White chalky residue on fiberglass pool

    We bought "Ultimate Scale and Stain Control" from Leslie's since the Scaletec version isn't found near me. The gal at Leslie's says that their version is simply Scaletec packaged under their label. I don't know if that's true or not, but we added it to the water when we started filling. I doubled the initial dose as per the label. The fill process took about 8 hours but towards the end of the fill cycle, I noticed whitish "flakes" (termed used loosely) floating on the top. If I tried to pick one up, it simply curled around my finger almost like very thin, opaque, tape. If I rubbed it, it left a white residue that was exactly like what I'd get off of the sides of the pool. In the water, you could dissolve it into a white dust (just like what would come off of the sides before I had added this stuff). As the pool filled, we scrubbed the sides like crazy and had white milky water.

    By the next morning though, the water had cleared and the sides already feel a LOT better with a LOT less white residue on your hands. (It reminds me of oxidation on aluminum siding.) While I had already prepared myself for a big heaping dose of patience (knowing it could take many weeks), I was surprised to see how much progress had already been made.

    We're still scrubbing and I'll continue to dose this on a weekly basis following the label's instructions. We'll keep scrubbing away at the sides until I feel like we've got it licked.

    I'm afraid to get my hopes set too high, but I do believe that I can actually feel the gel coat underneath and it feels fine. (I was sure that I'd already ruined the gel coat.)

    And...YES! I have increased my calcium hardness thankyouverymuch ;-/ Hopefully by the end of this summer, this problem will become a distant memory.
    Central Indiana, 7200 gallon, IG fiberglass, L250 Jacuzzi sand filter, Hayward H150 gas heater, Pentair fiber optic light - installed '06. AOSmith 1.0hp pump, CPSC-24 SWG - installed '13. TF-100 Test Kit.

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    Re: White chalky residue on fiberglass pool

    I am a new fiberglass pool owner and came across this reading up on my CH levels.

    "I do see from your chemical list that the Free CL is high 5ppm is very high. We recommend a range of 1-3 ppm. Also using Liquid
    Chlorine will cause gel coat damage over time."

    I hope this is the proper thread to ask this, but what is up with this MFG suggesting such things ? Is their any validity with it ?
    14,750 GAL IG Fiberglass (16 x 33) NE Ohio || Jandy 1HP 2 speed Pump || Waterco MultiCyclone 16 Centrifugal pre-filter (removed due to not working with sand filter) || 30" 575 Lb. Sand (Removed Original ECOSmarte Glass Media - AVOID AT ALL COSTS) Filter || AquaCal 140K BTU Heat Pump || Solar Cover || GLI Monsoon Solar Cover Reel || K-2006C Test Kit || BBB with Liquid Chlorine Stenner Injection || Rayner Mighty Mesh Winter Cover

  20. #20
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    Re: White chalky residue on fiberglass pool

    Quote Originally Posted by toofast
    "I do see from your chemical list that the Free CL is high 5ppm is very high. We recommend a range of 1-3 ppm. Also using Liquid
    Chlorine will cause gel coat damage over time."

    I hope this is the proper thread to ask this, but what is up with this MFG suggesting such things ? Is their any validity with it ?
    There is only validity with it if there is no Cyanuric Acid (CYA) in the water in which case they would be right that 5 ppm is high. They obviously have no understanding of the chlorine/CYA relationship that was definitively determined in 1974 in this paper. If they have anyone in their company who knows chemistry, you can refer them to that paper as well as numerous others in the "Chlorine/CYA Relationship" section of this post.

    At the minimum FC relative to the CYA level in the Chlorine / CYA Chart, the active chlorine (hypochlorous acid) level is the same (at pH 7.5 and 77F) as having an FC of only 0.065 ppm with no CYA and even our shock level FC is equivalent to only 0.63 ppm FC with no CYA. Even at higher temperatures at 90F, the minimum FC is equivalent to only 0.16 ppm FC with no CYA and the shock FC is equivalent to only 1.2 ppm FC with no CYA. Perhaps the manufacturer should start recommending people to use at least some CYA even in indoor pools where there is no sunlight so as to have their gelcoat last longer (and for a more pleasant swimming experience).

    We've had many fiberglass, vinyl and plaster pool owners as well as acrylic spa owners on this and other forums that understand the chlorine/CYA relationship and have not had any damage due to the higher FC levels so long as there is CYA in the water and that the chlorine (or any other concentrated chemical) was poured slowly over a return flow so that it was thoroughly mixed in the water and did not settle to the bottom.
    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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