Is this Calcium build-up or fiberglass gel-coat erosion?

[ChristenQ]

I opened the pool this spring to see the dreaded chalkiness below the water line! (Nooooo!) I hadn’t noticed this before closing last season and there was 0 chlorine and a 7.4 ph at opening. I’m clueless as to what happened unless maybe I didn’t notice the chalkiness last season as it was under waterline. Am I looking at gel-coat damage or could it be that calcium built up over the winter? What did I do incorrectly and what should I do now?

Here’s a link to my Poolmath test records: PoolMath Logs

 

[Texas Splash]

Based on your Poolmath log, I don't see anything recently that would point to scale. Maybe a year or two ago the CSI was allowed to stay elevated for a while, but I think you would've noticed it back then. When was your pool installed? Mine started showing signs of changing around the 2-3 year mark. As you can see, mine was quite significant, and it drove me nuts. I tried a lot of things to resolve it. But in the end, it may just be a natural changing process of the gelcoal itself - at least for some FG pools. Your chemistry logs over the past years or so, if indicative of most water conditions, look great. Nothing looks like you did anything wrong. What is unknown is if your gelcoat will continue to change. If so, there may not be much you can do other than keep the water balanced. We had a recent discussion with another FG owner HERE. Take a peek at the reply from one of our chemistry experts on Post #3.

 

[ChristenQ]

Based on your Poolmath log, I don't see anything recently that would point to scale. Maybe a year or two ago the CSI was allowed to stay elevated for a while, but I think you would've noticed it back then. When was your pool installed? Mine started showing signs of changing around the 2-3 year mark. As you can see, mine was quite significant, and it drove me nuts. I tried a lot of things to resolve it. But in the end, it may just be a natural changing process of the gelcoal itself - at least for some FG pools. Your chemistry logs over the past years or so, if indicative of most water conditions, look great. Nothing looks like you did anything wrong. What is unknown is if your gelcoat will continue to change. If so, there may not be much you can do other than keep the water balanced. We had a recent discussion with another FG owner HERE. Take a peek at the reply from one of our chemistry experts on Post #3.

Thanks Texas splash, our pool is almost 3 years old, so it’s consistent with what you have. It drives me crazy too. I can see patchiness on the steps and everywhere else just appears lighter and if the water level is down it looks chalky. I combed through that thread you recommended yesterday and although I skimmed the technical science stuff, that thread has me concerned that it’s damage to the gel coat. Although my CSI hasn’t been overly negative, I have never kept my CYA at the recommended 70-80. I’ve never thought to worry about chlorine levels are too high for my CYA of 20-30. I’m going Get some more stabilizer today and start keeping it at 70.

 

[Texas Splash]

I’m going Get some more stabilizer today and start keeping it at 70.

Remember though, the recommended elevated CYA level of 70 for salt pools is primarily to help with the efficiency of the FC produced by the SWG (which is slowly across the entire day and cell productions times). Non-salt pools don't always need a CYA of 70 unless they are in a very hot location with full sun on the water. Where you're at, you might get by with a CYA of 50 for now just because the heat/sun are not as intense and there is not a high FC demand. You do want a CYA of at least 30 for sure. So I would increase the CYA to about 50 or so for now That is plenty of buffering protection against the chlorine, so then it is really more an issue of does a CYA of 50 keep your FC constant & stable? As summer approaches, the CYA of 70 may be more applicable to your pool based on location, water temp, amount and intensity of sunlight, etc. In the end though, there may not have been anything you could do about the changes in your gelcoat. We conduct & record many evaluations over the years here at TFP for every pool type and possible condition. So far, we're not seeing a common denominator about this chalky issue which is why we suspect in many case it may just be how the gelcoat was manufactured and/or applied.

 

[ChristenQ]

Remember though, the recommended elevated CYA level of 70 for salt pools is primarily to help with the efficiency of the FC produced by the SWG (which is slowly across the entire day and cell productions times). Non-salt pools don't always need a CYA of 70 unless they are in a very hot location with full sun on the water. Where you're at, you might get by with a CYA of 50 for now just because the heat/sun are not as intense and there is not a high FC demand. You do want a CYA of at least 30 for sure. So I would increase the CYA to about 50 or so for now That is plenty of buffering protection against the chlorine, so then it is really more an issue of does a CYA of 50 keep your FC constant & stable? As summer approaches, the CYA of 70 may be more applicable to your pool based on location, water temp, amount and intensity of sunlight, etc. In the end though, there may not have been anything you could do about the changes in your gelcoat. We conduct & record many evaluations over the years here at TFP for every pool type and possible condition. So far, we're not seeing a common denominator about this chalky issue which is why we suspect in many case it may just be how the gelcoat was manufactured and/or applied.

Ah, that makes sense. I just read your pool story and see many similarities! First year was marked with positive CSI because I didn’t know better which resulted in scaling at and above water line resulting in bubbling with acid. I learned to keep a negative CSI and haven’t seen the scaling at and above water the line like before. Fast forward to 3rd season and a new below water line color change is different that the calcium buildup I had in the first year. It is below water line and doesn’t feel like build-up. In contrast to your story, I never maintained a CSI lower than -.60 (most time I’d say its closer to -.1) and I STILL have the same damage. This leads me to believe that something else is oxidizing the gel coat OR, as you suggest, it’s just a faulty gel-coat. My pool was fabricated locally, so I’ll give them a call, but after seeing the responses you and others have gotten, I’m not optimistic. ?

 

[ChristenQ]

I've been mulling over this mystery for days. Maybe it's really gel coat failure and I'm just in denial. BUT, the 2 things that keep standing out are 1. that I never noticed this until we opened the pool this season and 2. The picture I took this spring opening (see below) shows the whitening is staged and starts far below where we normally keep our water line. You can see three distinct stages of lightening. This would indicate it didn't happen during the season when the water level was higher, right? Could it be something our pool builder used when he closed the pool and lowered the water level? And then as the water level continued to drop over the winter it continued to lighten in stages? I've never closed the pool myself and I have no idea what they use. It seems like if you added something to the water and then turn off the pump, it wouldn't get mixed around well. It only takes them a few hours to close the pool, and I did find a couple bags of Color Brite Sanitizer leftover from them. I feel like I'm investigating a crime... I am!... the death of a young, beautiful gel coat!

 

[Texas Splash]

Like you, I go through periods of denial as well. But I doubt anything from closing was the result. At most, they probably increased the FC a bit and/or added an algaecide. Perhaps a little RV antifreeze. Nothing there that would seem to indicate a propensity for the gelcoat change. But keep good notes, test history, etc. While we assume this is an unexpected, unpreventable gelcoat reaction to well-balanced pool water, maybe there is something else to consider. Try not to beat yourself too much about it. I know, it's hard.