White deposits covering Fiberglass pool

[sbv16]

Hi

I have a 3 year old fiberglass chlorinated pool that has developed white staining from the water line and throughout the floor and walls of the pool.

Local pool stores are telling me it is etching of the gelcoat, the pool manufacturer is telling me it is calcium and that the pool needs to be drained, sanded and polished to remove the staining. Im also being told use of the pool blanket and too much chlorine has caused this.

Ive tried reducing the water level and applying undiluted hydrchloric acid directly to the white substance and it didnt touch it at all. 1200 grit sandpaper removes it but this is logical given its removal of gelcoat.

My past two test numbers are:

Two weeks ago
FC 6.37
PH 7.2
Hardness 73
TA 63
CYA 71

Currently
FC 3.67
TC 3.76
PH 7.4
Hardness 80
TA 112
CYA 68

The attached photos show the staining. When wet its not as visible but the white stains cover the pool under water line. Is there any way this can be removed with chemicals?

 

[JoyfulNoise]

Welcome to TFP

Sorry to hear about your troubles.

I am no FG expert but from what you describe it sounds like the gel coating has become compromised. The gel coat is nothing more than a clear fiberglass resin applied to the top of the fiberglass surface to protect it from mechanical wear and chemical attack. It itself is not immune to chemical attack and can get oxidized over time by chlorine and other chemicals. This usually leads to a roughening of the surface through the creation of microscopic porosity which you may or may not be able to feel with your hand. Once that porosity develops, dirt, calcium, organic "crud", etc., can build up in those pores and lead to an off-white/greyish colored film. The only to fix this is by sanding down the gel coat or removing it altogether and reapplying the gel coat. That is, unfortunately, a labor intensive process that requires draining the pool, bracing the pool to make sure the fiberglass doesn't shift and dewatering the surrounding area to ensure the pool doesn't float up out of the ground. Then the surface has to be stripped, cleaned and new gel coat applied. That's fairly expensive as you might imagine.

If you give us more details about how you operate your pool, what chemicals you use and how you measure your water chemistry, we may be able to help you find a way to balance the water so that the calcite saturation index (CSI) is slightly negative. Having a negative CSI and using some metal sequestrant might cause the stains to lighten over time but that is a long process and could take months or years to see if it has any effect at all. These stains did not develop overnight and they won't be fixed quickly...

 

[pooldv]

Welcome to TFP!

Calcium scale is rough and feels like it is raised above the surface of the pool. It typically builds up slowly over a period of time where the pH, TA and/or CH are at consistently elevated levels. More here, Pool School - Calcium Scaling. Sandpaper can be used to smooth scale but with fiberglass there is risk of damage to the gelcoat. Ask discussed in the article you can maintain negative CSI for an extended period of time ever and brush often to dissolve the scale. This will take about as long as it took for the scale to build up in the first place.

 

[duraleigh]

I agree it is an issue with the gelcoat. Pool Manufacturer may be your best bet or someone VERY experienced with fiberglass.

 

[Texas Splash]

sbv16, the replies above are from TFP pool owners, scientists, and/or experts who are widely respected and have been in the pool industry for decades. What I'm about to add (lengthy - sorry) is strictly my own personal (similar) observations in our FB pool. My apologies in advance for this lengthy reply, but it hits home for me as well. I feel your pain. Since our pool was installed in May '13, we've also noticed a change in our pool surface from the water line and below. In our case, it looks and feels just like calcium. The surface above the waterline is bright blue and showroom smooth. The minute my finger hits the water line and below it feels a bit rougher and looks lighter in color (chalky). Not bad, but like you, our pool is not that old either. I managed our pool for about a year before learning about TFP and proper balancing. I know I allowed my CSI level to reach 1.0 for too long (scale). In my case, before the discoloration, there was never a time where my CSI was ever too low which would promote etching. That may be something you wish to reflect back upon from the past 3 years. I also can't imagine that an elevated chlorine level would cause any harm, especially when a reasonable level of CYA (stabilizer) is maintained as a buffer agent.

I see your pool store and manufacture disagree. No surprise there. In regards to your pool store's comment about etching, most FB pools manufactures I have contacted do not use calcium-carbonate in the fabrication process, so you wouldn't think a low CH would be as detrimental to the surface like it would be for a plaster pool (etching). I'm not saying it's impossible, but our pool manufacture stated that it would be very difficult to damage the gelcoat as they apply numerous layers during fabrication. As a side note, it is still good to maintain an adequate CH level to protect the shell from staining (see TFP recommended levels).

Then your manufacture mentioned calcium. Our FB pools certainly can get scale. In my early days of pool ownership, I had a habit of letting my pH get a bit elevated. So an elevated pH, coupled with an elevated TA and local hard water (CH), was a recipe for calcium scale. Once I understood what happens when the "CSI-trio" of pH, TA, and CH becomes elevated, I believed that I may have allowed the situation (calcium scale) to occur. Again, that may be something you wish to reflect back on from the past 3 years if you kept testing records.

Now I keep a spreadsheet with all my daily tests. Since I attribute MY discoloration to scale, I have been trying to reverse that trend by keeping my CSI in the negative to see if there is any change. It's been about 1.5 - 2 years now and I've yet to see any real productive change. Perhaps a little bit better, or maybe it's my eyes playing a trick on me (wishful thinking). To-date, I'm not seeing the change I was hoping for yet. As noted above, perhaps it's simply that any attempt to remove scale via a lower CSI may take longer to remove than it took to get it on there in the first place. Not sure. As for other methods of calcium removal, we can't use wire brushes in our FB pools, and those so-called scale removers from the pool stores are useless. As noted above, we could scrub or sand an area and see a subtle improvement, but I can't do the whole pool that way, and I don't want to damage the gelcoat or end-up with an uneven appearance. I haven't tried what you did (acid directly along the water line), but perhaps I should as a test.

In the end ...... sorry, I said this would be lengthy. But in an investment such as ours, you want the pool to look showroom perfect for years. Any imperfection is frustrating. Since our pool discoloration is uniform, feels the same way throughout, and I know my CSI was elevated and NEVER too low (etching), I'm hoping it's just scale from my early "pre-TFP" days. I'm still optimistic that a few seasons of negative CSI may resolve it. Aside from the lighter color blue underneath, the pool looks great and everyone compliments us on the pool and water. Again, something that may help you is if you have records of tests and/or can confirm where your CSI level (pH, TA, and CH) was the past 3 years. That info may help give you a good path forward. I just figured I'd pass-along my own personal FB pool experience and let you know you're not alone. FB pools are pushed as being very easy to maintain - mostly because of their smooth surface. But they are not excluded from scale or other gelcoat problems if chemical levels are allowed to go unbalanced for a significant length of time. Hopefully we've given you some good information to go on. Best of luck.

 

[pooldv]

Lots of good info there, Pat.

I would say that etching in a FG is impossible since etching is the action of Calcium dissolving from plaster back into the water. Scale or damage to the gelcoat are the only two options. I agree that FC level is an unlikely contributor, especially in the presence of CYA.

Gelcoat failure in boats nearly always presents as bubbles, referred to as osmotic blistering, or becoming chalky. I've never seen gelcoat failure that is rough and white which makes me suspect scale. To make progress dissolving scale through lower CSI, the CSI needs to be -0.8 to -1.0 with regular brushing. But, that works on plaster pools, I don't know for sure if it works on FG pools. It should but maybe scale sticks better to gelcoat than it does to plaster.

There is an interesting discussion here that increasing CH to 300-350 reduces the chalky-ness, White chalky residue on fiberglass pool

 

[sbv16]

Thanks for all the replies

I agree with the comments re: chlorine levels. FC needs to be higher due to the presence of CYA.

What confuses me is that my test history doesnt show scenarios where the saturation index creates an environment for calcium build up. Historically Ive had stable ph levels, low TA and low hardness. We run a chemigem automatic sanitiser which offers some level of protection from ph and FC getting out of control.

If it was calcium wouldnt it react with the acid?

Its also worth mentioning that prior to xmas we did notice some white buildup on the steps and floor but the walls were fine, 2 or 3 weeks later when we returned from holiday and pulled the cover off we were greeted with staining over the walls which is especially patchy and ugly closer to the waterline.

Reading the other thread mentioned above it seems they had low CH and increasing the CH levels assisted. There is a clear history of very low CH in my pool.

My thinking right now is that before I proceed to drain, sand and refinish the pool it might be worth lifting the CH to 300, reducing ph a little and adding a calcium treatment. There are specialty stain chemicals offered online but they are expensive and I'm not confident they will work given acid was unsuccessful.

 

[Texas Splash]

If it was calcium wouldnt it react with the acid?

You would think so which is why I believe test history is so important in your scenario. The fact that you believe your CH, pH, and TA have always been low enough to control your CSI tends to suggest something other than calcium. Have you considered asking your pool manufacture if they use calcium-carbonate in their shells? Just a thought.

 

[pooldv]

Definitely doesn't hurt to see what they say. Does it feel raised or pitted? Etching results in pits left in the surface and scale is deposited on the surface. I've had both and they are distinctly different. How did you apply the acid? Did it fizz at all? Can you scrape some off, put it on a plate and put a little acid on it to see if it fizzes?

 

[JoyfulNoise]

I agree that FC level is an unlikely contributor, especially in the presence of CYA.

I agree with the comments re: chlorine levels. FC needs to be higher due to the presence of CYA.

I actually disagree somewhat with these statements - chlorine levels are important. Just because CYA is present doesn't mean that chlorine stops reacting with "stuff". The reactions still occur, just at slower rates.

Fiberglass and gelcoats are nothing more than unsaturated polyester resins with glass fibers spun into them, or, in the case of the gelcoat, just the polyester resin itself. These materials are polymers with a large fraction of unsaturated carbon-carbon bonding. Unsaturated bonds are much more reactive than saturated bonds. This means that oxidizers can and will cleave the polymer at these bonds turning a highly cross linked polymer chain into a simpler and smaller sub-units. The net results of this is that the surface layer of the gelcoat will have different mechanical properties than the underlying bulk material. Thermal cycling can and will lead to crack and void formation. This is a common problem in all polymer systems that are subject to environmental degradation. It is these voids that, over time, grow and form into areas of increased surface roughness where dirt, organics and scale can more easily develop. One place where you see this often is the rubber "boot" on the tops and bottoms of the filters that make up a cartridge (and some DE) filter systems. Over time, chlorine reacts with the rubber and degrades the vulcanization (essentially sulfur cross linking bridges) and causes the rubber to degrade. You can rub the degraded, tacky rubber off with your fingers and expose what looks like fresh solid rubber underneath.

Normally clear or transparent polymers that have rough, degraded surfaces with chemically induced porosity and cracking look white or grey colored. This is a consequence of light scattering at the surface.

This is also why I think the manufacturers require a certain level of hardness to the water. Water that has a saturation level of calcium carbonate in it (LSI and CSI values near zero or slightly positive) will tend to deposit a very thin layer of calcium carbonate at the surface of the fiberglass thus acting as a protective barrier. If the FG is constantly exposed to chlorine, then degradation will occur; if there is a calcium carbonate layer in between, the polymer will be mostly protected. Excessive hardness will cause more visible scaling.

SO, to the original problem, I think the only permanent solution is to have the FG resurfaced if you want to get it back to its original look. Otherwise, I don't see any clearly easy chemical method that is going to fix the degraded FG surface.

 

[sbv16]

These are my last 7 test results going back to March 2015

March 2015
FC 5
TC 5.27
PH 7.8
CYA 59
TA 129
CH 138

September 2015
FC 3.03
TC 3.24
PH 7.4
CYA 33
TA 85
CH 94

May 2016
FC 0.88
TC 0.94
PH 7.3
CYA 28
TA 35
CH 76

December 2016
FC 2.59
TC 2.75
PH 7.5
CYA 16
TA 92
CH 78

January 2017
FC 6.37
PH 7.2
CYA 71
TA 63
CH 73

Current
FC 3.67
TC 3.76
PH 7.4
CYA 68
TA 112
CH 80

Manufacturer doesn't use calcium carbonate in shells. There is no pitting on the surface it looks more like a deposit, but it doesnt feel rough at all. Acid was applied by pouring some directly onto surface and was also applied by dipping into a cloth an rubbing on surface. Acid was left on for a few minutes then washed off. Its not possible to scrape it off even with a sharp blade

 

[Texas Splash]

sbv, as you can tell from Matt's reply in post #10, he knows his science. Speaks a language above my pay grade. :blah: ha. Your test results are hard to rely on too much only because there are only 7 listed, but if I was to use those 7 results in somewhat of an "average" indicator to see how the water has been maintained, the Poolmath calculator places your CSI somewhere close to -0.94 which typically places a surface likely for corrosion. With such a low CH level, it certainly could leave the surface exposed to staining or perhaps chemical intrusion. Your pool doesn't have calcium carbonate, but based on Matt's comments I can't help but wonder if the shell wasn't somehow subjected to some chemical penetration that resulted in that discoloration. Who knows, even with the best of care some chemical penetration may have ensued. I know our FB manufactures push these pools as almost maintenance-free, but when you mix water, chemicals, and the sun together, you're bound to see some reaction. That may be what's happening to me as well. The fact that you see no effects at all by adding acid would seem to rule-out a calcium. More of your indicators seem to point to the fact that the gelcoat was somehow penetrated.

In the meantime, please consider updating your signature with all of your pool info (to include what test kit you are using) by clicking EDIT YOUR SIGNATURE. It will help us later. Thanks very much. Keep us posted on any other developments or questions. I'm going to try applying some muriatic acid this afternoon if it's exposed at the waterline so we can compare notes.

 

[pooldv]

Agreed, application of acid as you did would have had an effect on scale. Also, not being able to scrape it off indicates that it isn't scale as well.

There are DIY gel coat products available in the boating industry, but as you would imagine it is a tremendous amount of work.

As for Matt, those poly unsaturated vulcanized cross linked polymer sulfers will get you every time!

 

[JoyfulNoise]

Yeah, I hesitated writing any of that because I did not want to muddy the waters with a lot of technical jargon. The fact of the matter is, all pool surfaces, be it plaster, fiberglass or vinyl, are subject to chemical degradation from pool water. There is simply no way to avoid it and some surfaces just hide it better than others. While fiberglass is often touted as a "chemically inert" surface and "easy to care for", it develops weird problems of it's own too (e.g., cobalt spotting).

I will make one generalized comment about the OP's pool though - don't assume that because you have a ChemiGen control system that your water is always balanced and/or at the correct levels. Like all automated chemical dosing systems, those that use ORP and pH probes are subject to fluctuations in chemistry if those systems are not properly calibrated. If you search our forum with the terms "ORP" and "automation", you'll find that TFP takes a fairly dim view of all the chemical control systems. They are often touted as "simplifying" the management of a pool but what they generally lead to is a lot more frustration and things that can go wrong. Nothing beats daily testing and dosing of the water's chemical levels using a high quality, liquid drop reagent test kit like the one's from Taylor Technologies or TFTestKits.net. I realize that being in Australia limits your ability to get a good test kit but, last year, a new player came on the market in your region of the world called Clear Choice Labs. They make a pool test kit very similar and competitive to the ones we have here in the US and many Aussies have given them a try and found the kits to be quite useful. If those test results are from a LaMotte ColorQ (also another gadget TFP doesn't feel is worth it) or the local pool shop, then I would respectfully suggest you consider getting a reagent based test kit and do, at a minimum, weekly in-depth testing of the water yourself to make sure your system is not only giving you a proper readout but that your water is better balanced.

Good luck and let us know if the manufacturer is any help with your staining issues.

 

[pooldv]

Matt, my comment notwithstanding. It was good info and informative. I'm glad you posted it.

 

[PebblePool]

I concur with the consensus that your gelcoat is worn. I have a gunite pool that was re-surfaced with fiberglass a decade ago, well before we bought the house. The surface looked smooth when full of water, but there was white residue always on the surface. The surface looked smooth when filled with water, but once they emptied it to re-surface it, it was apparent that the gelcoat was shot, because you could see the fiberglass strands exposed.

 

[sbv16]

Thanks again for all the replies

Im starting to accept the fact that this probably isnt coming off via chemical treatment.

Looking back to when we first got the pool I remember having issues with whitening of the pool above the waterline and Iv always scrubbed above the waterline with a majic eraser which probably explains why the pool is only affeted below waterline level. This is my first pool and as you can imagine Im wishing we had been even more thorough with maintenance.

The manufacturer has been a bit underwhelming to be honest. They are claiming some of my test results are "off the charts" which I dont agree with. Clearly there is an issue here given the pool store had photos of the exact same problem in other relatively new pools and the chemical manufacturer rep said they have seen a substantial number of pools with this issue and could not treat the problem with chemicals.

As mentioned above lightly rubbing back the gelcoat with 1200 grit wet sand paper removes the staining. I think that a cutting compound on a rotary polisher would remove the staining. Im waiting for the manufacturer to advise how to brace the pool safely prior to draining but im not sure theyre going to respond.

Their directions are to sand and buff the pool and that this has worked for them in the past. Iv confirmed this per the above.

 

[sbv16]

Hi again

Prior to proceeding to drain the pool I would like to make sure I brace it properly to prevent any movement.

The manufacturer gave me some general directions over the phone but hasnt replied to my email so Im not going to hold my breath waiting for a response.

Ive drawn on a plan of my pool the two options for bracing in red. I propose two braces accross the width of the pool. Not sure if two is sufficient or weather they should go accross the top of the seat or below the seat as shown.

If anyone can advise the right way to go about this that would be great. Ive seen images on the net of people bracing using timber alternatively I could use propping tools specifically for propping loads.

I should add Ive checked the water table levels here and the pool is a few meters above groundwater level so should be ok from that perspective.

 

[gwegan]

You want the braces on a ledger board so as to spread ot the effect of the braces.

Even though you think you know where the water table is I would sink a couple of dry wells at either end of the pool before you drain to be sure the water is several feet below the pool.

 

[saba_developments]

If I am not being too nosey, you may just want to double check a few things (As I know a little bit about Aus pool warranty issues). Not know your manufacturer, ill stay a bit general but a key player in pool Gelcoat in OZ would suggest ideal Calcium Hardness levels to be no lower than 175 and no higher than 225. Of course the pool company may make their own but many in AU are supplied by the manufacturer. If you have had a few years out of that range in the lower end it may have some bearing on the problem you have now. But the manufacturer should be able to assist. Im not sure if you have a warranty on the pool but if you do and its IE 10 years or Life structure, be careful you don't void that warranty by emptying the pool.

Strutting the pool (Scaffolding irons are easiest but be careful where the bars or wood go at the point of being on the gelcoat as if there is too much pressure you may star crack the GC) You may want to use more than 2 struts, depending on the earth around the the pool. If you have a valid warranty, if the dealer is lapse - do try to ensure its clear you can empty the pool even under their instruction and maintain the warranty. A cutting/rubbing compound with a rotary drill should do the trick. But do wax it with a turtle wax or similar afterwards. If you have used 1200 you may want to go over that area with the rubbing compound then wax as well. Do be careful putting straight Hydro Acid on the GC as you may bleach the pigment.