Calcium scale and negative CSI in fiberglass pools

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S

seribus

Well-known member
Jun 9, 2016
60
NC
Hi All,

Long time lurker. I’ve been battling a calcium scale issue the last few years and trying to get answer. Will keeping CSI in negative reverse calcium scale on its own and dissolve back into water?

I have the classic chalky areas on walls, floors, steps and seats. I have used a piece of 600 grit sandpaper to wipe across surface and I see a white trail that exposes the nice sparkle blue color of tub. Can almost scratch with finger nail in some places and expose blue surface. Also have done acid test. I’m sure there is some calcium silicate too but not bad. I thought I was being meticulous on ph but maybe possible I let it drift as I was learning. I also thought I had a bad salt cell and swapped it this year.

Long story short is I added SWG in 2016 and almost immediately started having issues. Called (Tallman) manufacturing and they suggest jacks magic and I’ve tried scaletec. I have a jug of scaletec now but haven’t dropped it in. Threw some in at closing and during winter.

I gave up on the SWG a few times since install and went back to pucks for fear it was causing issue. The first summer having SWG it’s possible I let ph get high but even then I always brought it down. Since then I am on top of ph but no avail on scale.

This is year I plan on being OCD about CSI in hopes keeping it negative will reverse this scale. That’s what I hope you all can tell me or how to tackle this. I use Taylor 100 kit and have plugging numbers into pool math to make sure CSI stays negative. The water looks great right now which shows off scale.

Numbers have been about the same since April 24th. I did SLAM the pool on April 22nd to FC 28 ppm and let it drift back down to FC 7. I didn’t stop SWG but backed it down to 20%. Only chems added so far is algaecide and clarifier. Shocked with cal hypo. Started on pucks right after open and shocked because algae was eating my FC each day.

FC 7
PH 7.2
TA 80
CYA 80-85
CH 250 I added some this year to reach that. Historically very low CH. started year at 160
Salt 3500
water temp 76

This scale is driving me nuts and look forward to your replies.

Thanks,
Carl
 
Re: Calcium scale and negative CSI in fiberglass pools

Based on the chemistry, it might not be scale.

Sometimes fiberglass gel coat or acrylic will break down and chalk up.

If you rub your hand on the surface, does it create a white cloud or leave white residue on your hand?

If you can scratch up some sample, put a drop of acid on it to see if it bubbles.
 
Re: Calcium scale and negative CSI in fiberglass pools

I’ve been battling a calcium scale issue the last few years and trying to get answer. Will keeping CSI in negative reverse calcium scale on its own and dissolve back into water?
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If what you are seeing truly is calcium scale, it certainly could help. However .........

Carl, myself and some others are tangled up in some other threads about this very issue. Here's what I've gone through to-date:
- Installed May 2013; I wasn't smart yet on pool care; focused on algae more than anything; After finding TFP, algae no longer an issue but I believe I still let pH stay on the high end
- In 2015, started to see changes as you describe; always believed it to be scale; I've been tracking my daily chemistry on a spreadsheet since then.
- Got serious about the chalkiness in 2017, keeping my CSI low (about-0.6). Tried an occasional bottle of ScaleTec with no change; on advice from local installer, did some manual sanding; like you would see the cloud of white followed by original color; all assumed it was typical scale; I drove my CSI even lower now - very low for several months.
- Dec 2017, installer requested more aggressive use of ScaleTec then they would upchannel to manufacture (Viking, Lathan, etc often times under same warranty representative)
- In good faith to my installer, I (reluctantly) used two bottles of ScaleTec per month for a few months as directed and kept my CSI extremely low but still no change
- Apr 2018; Warranty dept contacted me with specific testing instructions; lowered water level to expose first step and poured undiluted muriatic acid on it - NO EFFECT. That was very disappointing. At this point they ruled-out calcium scale and pointed more towards an oxidation effect. They "claim" that chlorine levels over the recommended 1-3 ppm (regardless of CYA) is a prime contributor. Ironic in your case, they also implied that SWG owners could experience this effect for not controlling the FC generated. (I don't think they appreciated my reply when I expanded on the FC/CYA relationship). :)
- All of those FB manufactures are quick to point out that unless an owner has documented/recorded pool testing from an authorized location (i.e. pool store) the warranty is void. :rant: :rant: That is perhaps the biggest irony in all of this as we all know the disparities in pool store testing and how awful the advice is. Still, I suspect as a company they have to have "some" way to protect themselves, otherwise everyone would complain and say "My chemistry is good" even if all they have are test strips - which is exactly what my installer handed me at our pool opening. :grrrr:
- This year I'm experimenting. I'm doing a more thorough, aggressive sanding approach which is very tiring. I'm using 200 grit wet/dry followed by 600 wet/dry and sanding until I see what I see the original color. Interesting at this point though, I'm not kicking-up that white "cloud" when sanding like before. At this point, I'm no longer driving my CSI down, but keeping it "slightly negative" (-0.3 ish) with all other parameters in standard TFP range. I expect one of two things to happen: The blue will get chalky again in a few months which tells me that the combination of chlorine and sunlight will oxidize gelcoats regardless of what we do; OR, what I physically removed was indeed some sort of calcium by-product that was embedded in the gelcoat from my early days in such a way that chemistry (even straight acid) had no effect and it had to be physically removed.

Today, after a couple solid years of frustration, anxiety, and exhaustion about all this, I'm at peace. I had my discussion with the Viking/Lathan warranty Dept, I know their position and they know mine. While I know the surface is lighter now, most visitors have no idea and see a lovely (blue) pool. I'm good with my pool care and love how it looks. I am however going to continue my sanding experiment which will take me through this entire year and probably into 2019 just to manually work on the areas I can reach. Beyond that, I'm going to watch for any changes later and see what happens and share that with everyone here AND the Viking/Latham manufactures.

Carl, what you are experiencing is more common than FB manufactures probably care to admit. They will quickly point towards owner/user failure to maintain (antiquated) chemistry standards, and in some cases I'm sure that's true. But there are many owners who test their own water daily (properly) while maintaining optimal chemistry and still have this issue. There may be other scenarios at play here other than simple calcium scale (i.e. oxidation) that FB manufactures fail to address at the risk of losing a large new customer base.
 
Great post Pat. I know you've been working this for a long time and I've been following along with interest. I think you are right on target toward figuring this out.

I tend to think that it is an inherent problem with gelcoat because this also happens to boats in freshwater and in the ocean. The boat bottom will chalk up after a few years of being submerged. It's enough of a problem that if you plan to leave a fiberglass boat in the water for extended periods of time then they recommend using bottom paint on the boat to protect the gelcoat and prevent chalking, osmotic blistering, etc. That might be another place to do some more research next winter. :)

I added fiberglass pool to the thread title to help differentiate it.
 
Thanks for the quick responses everyone.

James, no residue when I rub across it. I can't really scratch any up but I have poured muratic acid on my stone tile border at waterline and it bubbles there.

Last year I sanded some areas in testing and those areas you can still see the darker blue. I tend to think scale over oxidation because of where the chalky look is. It's most obvious in seats, steps and ledge around deep end. You see it at the curves. It could be coincidence but this came in with me adding the salt generator. I had pool a year previous and no issue.

If it's oxidation that's very discouraging. You know the manufacturer and pool installer probably have a few complaints on this but when I've called they seem surprised and blame SWG and push me to add scale chemicals.

I can say fairly certain I've never had pH over 8 for any length of time and only this year I did a SLAM up to 28ppm. Never been much over 10ppm ever until just recently. I'm miffed at the issue and hope just keeping csi around -0.6 helps. Until water temp gets up it tends to be around that anyway. Again maybe I did do something wrong on pH in the beginning but I feel I was on top of it.

I'll throw scaltec in today but it says to turn off SWG which I don't really want to do. If it oxidized evenly it would at least not be as noticable. I wonder if the areas of noticable scale\ chalk are due to how the Jets flow? When I got pool vacuum I was lazy in brushing steps, seat and ledge and that's where it's noticable.
 
Hi James,

Today I took a piece of 600 grit sandpaper and swiped across the wall and got some very light blue residue. I scrapped it off and dropped muratic acid on it and no bubbling at all. Maybe I have some little scale here and there but starting to looks like issue is oxidation after all. I don't get any residue by simply rubbing it with my hand. Only with sandpaper.

After that I called manufacturer and sent some pics. I doubled down and called another pool manufacturer/installer that I have no affiliation with to get an idea what they'd say. Not much to go on I'm afraid.

Wish I knew what the norm is for these fiberglass pools. Is oxidation and fading common with darker colors?
 
If it's oxidation that's very discouraging. You know the manufacturer and pool installer probably have a few complaints on this but when I've called they seem surprised and blame SWG and push me to add scale chemicals.
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Yep! Exactly what they told me. :grrrr:

I wonder if the areas of noticable scale\ chalk are due to how the Jets flow? When I got pool vacuum I was lazy in brushing steps, seat and ledge and that's where it's noticable
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. I doubt it. Mine did the same thing in all areas for no apparent reason.

Today I took a piece of 600 grit sandpaper and swiped across the wall and got some very light blue residue. I scrapped it off and dropped muratic acid on it and no bubbling at all. Maybe I have some little scale here and there but starting to looks like issue is oxidation after all. I don't get any residue by simply rubbing it with my hand. Only with sandpaper.
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Ditto.

I'm done with those people (manufactures). I'm going to continue with my process above in post #3 and will be happy to keep you posted as well as we seem to be in the same fiberglass boat. In my case, I'm hoping to find out once and for all what contributed to my color change and I'll be happy to share when I learn more.
 
Thanks Texas and please do let me know and I will keep updates posted as well.

At this point I just want to know the facts or truth. I want to Know for sure what is and what caused it. If there is a fix. If it's typical to fiberglass pools I want to know. If it's a gelcoat manufacturing issue I want to know. If I somehow did it in ignorance I want to know. I've beat this thing to death rehashing if I held the chlorine too high or pH too high at some point. I don't think so but possible.

It's not horrible looking yet but I notice it and I want stop whatever is causing it if possible.
 
Tallman pool manufacturer is sending someone out to take a look. Ill post what I find out.

Is there such a thing as salt scale? I swear it seems when I use swg the scaling starts up.
 

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I will run my numbers again tomorrow. Supposed to be good and hot in Carolinas this weekend. Should get some use. My CSI has been pegged at -0.6 since opening. I suspect it will move off that a bit as temperature rises.

As I understand it at present readings I shouldn't see any new scale correct and maybe some reversal if any is present?
 
As I understand it at present readings I shouldn't see any new scale correct and maybe some reversal if any is present?
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In it's simplest form, that is correct. Since I maintained a CSI of much lower than yours for several months, and poured undiluted acid onto the top step, I know that my fading is either not scale, or somehow interrelated to something else in the gelcoat. That's what puzzles me and I was not confident with the feedback from the manufacture. I'm pulling out of my exceptionally low CSI and watching this very closely in my gelcoat as well, but I suspect I won't have good data until the end of this season. In the meantime, I'm manually working on some areas to revive the blue so I have a good sample areas to compare to.
 
Manufacturer sent guy out today and as I expected they put onus on me. He stated it's not oxidation but a buildup of some sort. So we're going to watch a spot I've sanded on a year ago and at seasons end see if things are better or worse. So I still don't know 100% whether its scale or oxidation. He mentioned everything from winter closing chemicals, swg, to no clue but not oxidation. Supposedly if by September if spot I sanded is still clear they will come out and sand discoloration away. At this point who knows.
 
Put some acid directly on a spot. If it's calcium carbonate scale, there will be a reaction.

Note that there are other forms of scale that can happen, but they are rare.

Calcium phosphate, calcium sulfate and calcium silicate are other possible forms of scale.
 
Manufacturer sent guy out today and as I expected they put onus on me. He stated it's not oxidation but a buildup of some sort. So we're going to watch a spot I've sanded on a year ago and at seasons end see if things are better or worse. So I still don't know 100% whether its scale or oxidation. He mentioned everything from winter closing chemicals, swg, to no clue but not oxidation.
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I guarantee our gelcoats look the same, but interesting we received different replies from the manufacture - mine leaned towards oxidation. I'm not confident they really know at this point what it really is, and as you stated (and they did to me as well), they try to hold the owner responsible. I too am doing the same by sanding some areas and will watch VERY closely as the season continues.
 
Honestly it's making me bipolar. Depending on the day and how the sun hits it one moment I think it's getting better and the next time I look I'm doubtful and think it's getting worse.
 
Depending on the day and how the sun hits it one moment I think it's getting better and the next time I look I'm doubtful and think it's getting worse.
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Exactly! Been there and have been doing that as well. :) We're optimists right? :crazy: It's all the way the sun penetrates the water depending on the time of day, angle, cloud cover, etc. I'm 99.9% confident in my assessment of calcium silicate now and I'm still sanding away. I don't expect to do the entire pool, but I do want to hit the waterline down to a couple feet and some other areas this season to help it blend better. One day I might find the perfect tool that will help me zip through this process, but for now it's lots of elbow grease. At my age, there's not much grease left. :) Once I make some serious headway and have more data collected, I'll post a new thread of my own about my experiences and put a link to it in all my fellow "FB chalkiness" owner's threads - like yours. :)
 
Hi seribus,
It sounds like I have a similar situation as you, but I can't figure out what's causing it. Our installations are almost identical. I have had no success with the pool installer so I'm working with a local pool company. In one of your posts you said you can see it at the curves. That's the one place I don't see it. It's covering almost the entire pool. Sides, bottom, stairs, ledges, but not the curves. The pool company said all our readings were great except the calcium was a bit low, but they didn't want to add any until we figure this out. It's driving me nuts too! I'll let you know if I find anything that works.
 

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