Fiberglass Discoloration (Faded & Chalky) - My Story

[Rossterman]

The fiberglass construction and gelcoat is the same. True, wax will not last as long in a pool environment compared to a dry side of hull but it still helps protect. Restoration is the same as the chaulking comes from The same UV oxidation that damages boat fiberglass.

 

[crankin12864]

What grit sand paper and or polishing / waxing did you use?

I have exactly the same issue in a dark blue pool that I have.

 

[Rossterman]

All you should start with is rubbing compound. If really bad 800 grit wet/dry Sand first. Finish with polishing compound then wax.

 

[greggjess]

​

I stumbled upon this thread while researching calcium hardness and if I need to raise it or not. Anyway....do you (or anyone) have a thread on recommended maintenance of FG that might not already be covered? Like the brushing? Should we be doing that regularly beyond cleaning?

 

[YippeeSkippy]

Brushing is always a good idea..... once a week is ideal.... most of aren't *that* good. But now my robot scrubs the wall as he climbs up the walls randomly.

My CH is about 200ppm....its there "Just in Case" since I doubt I really need it but don't want to risk it,

 

[Texas Splash]

So about 2 years ago (2 May 2020), I posted the following pic (test spot) on page 1 of this thread:

Two years later it's almost completely gone as you can see from the pics below. The fresh (dark) area on the left is a new test spot I sanded today.

The past two years I continued to maintain a fairly balanced (neutral) CSI level just in case by some miracle there was some odd phenomenon about a low CSI that might be effecting the gelcoat. But that does not appear to be the case. It was also at this same time 2 tears ago I started using my SWG, so I hoped that perhaps the elevated CYA level, but lower FC level, might help buffer the free chlorine a little better than when I was feeding the pool manually with liquid. But that theory also failed.

So today's new/small test strip is just that - a new test. No huge expectations as I don't plan on doing much of anything different to the water chemistry. The pool is always TFP balanced quite well. While there are different forms of discoloration (chalkiness) with TFP FG pool owners, mine appears to be the type that proves a gelcoat is not impervious to the effects of treated water. Perhaps the amount of change could also be related to the quality of the batch of gelcoat and/or how well it was applied, but I don't know if we'll ever confirm that suspicion. Much like marine materials, the gelcoat will eventually absorb products and react accordingly.

No sense trying to fight a losing battle. The pool still has a lovely natural ocean blue color to it through the water. This adventure has been more about my pool OCD than anything, and a desire to experiment on my own. For now, let it go and swim.

 

[JoyfulNoise]

Gel coats are not impervious. They are essentially a polymer material submerged in water. Even with low or no chlorine, the gel coat will deteriorate from sunlight and water exposure. Microscopically if you could look at a thin cross section of the shell material, the surface would simply look like is has micro scale roughness and porosity. It is those pores and roughness that cause the specular reflection of light which appears as a “fog” or “haze” to the surface. When you sand the surface, you remove all of that porosity and leave behind a smooth finish. Then the natural color of the FG comes back.

Unless you drained the pool and had some professionally rework the gel coat, there’s nothing you can do chemically. And who would want to drain a pool every two years and pay someone tons of money to do all that work.

As you say, swim and enjoy.

 

[Jracka]

I know white fiberglass was mentioned previously, would I be safe to assume the lighter the FB pool color, the less fading would be noticeable?

 

[Texas Splash]

Welcome to TFP @Jracka! You would think so right? But I'm not sure how those gelcoat layers react if they were originally produced with white pigment. Would the chalkiness actually match?

 

[Nannyspool]

Wow thanks for sharing your story. I have a fiberglass pool with SWG and have yet to figure out my issue. It’s white everywhere below the water line (for the most part) but it’s not “chalky”. Nothing works but I’ll keep trying.

One thing in my case I wanted to shed light on for you is that we didn’t have a problem for the first couple years. We only noticed the build-up of whatever it is AFTER we installed our heat pump. Given our location and number of hours of sun v. shade, without a HP our pool temp ranged between 70-80 degrees. With the HP we keep it around 85-90. That’s when we saw the issue. It seems the warmer water caused the problem

Any thoughts?

Same here, after we installed the solar heater it all started.

 

[csconner]

Interesting observations, I’ve used HP since year one, but once I adopted TFP recommendations for water balance the white scaling has not advanced.

 

[YippeeSkippy]

I know white fiberglass was mentioned previously, would I be safe to assume the lighter the FB pool color, the less fading would be noticeable?

I dunno?.... I once saw a white fiberglass pool looked yellowed.

 

[Flying Tivo]

I once saw a white fiberglass pool looked yellowed.

Most probably used the wrong type of resin/epoxy or a bad batch.
You really cant compare a Gelcoat on a boat to a pool, the pool is under constant attack by FC oxidation. In boats UV is the main enemy, but nowadays most resins/epoxy have UV protectors.
It would be nice to compare a FG indoor pool to an outside pool, both following TFP guidelines.

 

[beachbabeBrandy]

Hey Texas Splash! Any updates on this?

 

[Texas Splash]

Hey Texas Splash! Any updates on this?

Still some testing in progress. In Post #26 you'll see my current test spot which is off to the side of the LED light. That area has not yet faded like the first test area I did exactly over the LED light. The only real difference in my chemistry is that in 2019 I installed the SWG and therefore increased my CYA to the 70-80 range and my FC is lower than when I was jumping liquid. So I'm still watching to see if there's any connection. In the grand scheme of things, I know gelcoats are susceptible to reacting with water whether it be due to salt, chlorine, sunlight, or all of the above. But interesting enough there are some very dark spots around the pool when it was fabricated at the factory that haven't changed a bit. Almost like these spots & droplets were of a difference consistency or something to where they are not effected at all and haven't changed since day one.

 

[RookiePick]

Really interesting topic for the FG poolies...sorry you are the guinea pig TS!

I trawled quite a few of the "FG pool gone chalky" threads the last couple days and while not doing a thorough analysis my gut feel was either of/both TA and CH were very low on the bulk of the effected pools. pH seemed typically at the more alkaline end and TFP levels of FC.were common.

I certainly not claiming any causative relationships and a more careful collection of data and analysis (plus testing of any concepts) would be required but maybe there is something there. Low hardness (softer water) and high pH is probably a bit unusual in the normal course of events but possibly it can be induced where pH is kept high to achieve a "better" CSI number but TA is suppressed to try and slow pH rise and CH is ignored as a relevant measure in an FG pool.

This circumstance is also plausibly induced inadvertantly if the FG pool has water features or similar providing aeration. The owner responding to the pH lowers TA over time via acid additions but continually pushes pH higher with their outgassing?

Perhaps something in this low hardness, higher pH situation makes the gel-coat particularly susceptible to bleaching?

Looking at my manufacturers recommendations for TA, CH, pH and CYA yields CSI ranges of -1.05 to -0.12 at 20C but of course the FC recommendations are well below TFP standards.

Scary stuff in any event when no one seems to understand the mechanism!

 

[Texas Splash]

Figured it was time for a little update. Below is a pic of the shell near an LED light I use as a test area. I had to lower the water level about 16" to replace the return jets, so this was a rare opportunity for me to see everything below the waterline without water effecting the view. Compare the pic below to the pics above in Post #26 which show changes in the two test areas above and next to the light from 2020 thru 2022.

 

[Texas Splash]

I considered sanding/buffing the exposed gelcoat while the water level was down, but decided not too. IMO, it's a fruitless battle where this gelcoat will eventually begin to fade from the effects of sunlight, chlorine, etc. Additionally, I want the shell to last as long as possible and have a concern that continued aggressive sanding would eventually erode too much of the gelcoat and reach the fiberglass shell itself. When full of water, the pool looks great, just like a pool with a white color, so we've adjusted to what we have and enjoy our pool.

The chalky transition is explained (scientifically) very well by @JoyfulNoise in his replies above. The thing about the pic below is that if you zoom-in closely, you'll see tiny dark spots in the shell that remain unaffected and retained their original deep blue color. There are areas like this all around the pool. In my opinion, this calls to question quality of the gelcoat - either the batch that was mixed and/or how it was applied.

We have a FG pool survey HERE in which TFP continues to evaluate FG pool conditions looking for any notable reasons that may help to explain why some gelcoats change, but to this point there is nothing substantial. Simply put, some gelcoats change while others do not. To-date, there is no correlation to the method of chlorination, FC, CYA, or pH levels, if maintained per TFP recommended level ranges.

 

[Texas Splash]

I also want to highlight for anyone just seeing this thread that this is not a scale/calcium issue. With my steps exposed, I could pour 31.5% strength muriatic acid on a step and let it sit with no changes at all. No fizzing, bubbling, or anything of the sort related to calcium scale. As such, attempting a no-drain acid wash or using countless bottles of ScaleTec-type products would be a waste.

 

[Texas Splash]

For those who may be interested, TFP conducted a survey in Oct 2023 regarding fiberglass pools in an effort to obtain information that might help us better understand why some gelcoats change (fade, chalky, blister, peel, etc) while others remain unchanged. You can review those results in the link below.

Fiberglass Pool Owners - Survey (Results)

Fellow TFP fiberglass pool owner, TFP is always gathering data in an to increase its extensive knowledge base and analyze that information to provide members with the most accurate and reliable information possible. As such, we developed the following survey in an effort to capture...

www.troublefreepool.com