Max Chlorine PPM for Fiberglass Pools

[ThePoolFool]

Fiberglass pool owners: Anyone know what the recommended maximum for Chlorine PPM is for a white fiberglass pool? For my spring startup regimen, I have been treating my water with 18 ppm using Chlorox (checking 2 or 3 times per day), and I was wondering if it is safe to go higher than that.

[waterbear]

From my understanding fiberglass pools are not affected by high chlorine levels. In fact, my builder used straight 12.5% chorine to get some organic stains off the surface while mine was being installled. Don't know if that was good or bad but it didn't hurt the pool at all.

If you have no CYA then that level might be a bit high but if you have high CYA then that level is not high enough. See this thread for details
http://www.poolforum.com/pf2/showthread.php?t=365

[duraleigh]

Poolfool,

I don't have an answer but am bumping this back to the top. I'm like waterbear....I think it's okay to boost it (Cl) way up but I'd like to hear some more confirmation.

[duraleigh]

I'm bumping this to the top once more. I am really interested in a definitive answer. Not doubting waterbear....I think he's right..... but I am hoping some of you FG owners can confirm.

If FG is not suceptible to Cl damage, It would seem to make sense to advise much higher levels when shocking a gunite or FG pool.

I constantly see posts from algae-ridden users who "tip-toe" up to shock level and, because the FC starts to drop the minute they add the dosage, they never obtain shock (breakpoint)....prolonging their agony.

Am I correct in assuming that suggested shock levels for FG or gunite pools could safely be raised say to 50% higher levels than we currently suggest for vinyl pools?

[DavidD]

I don't have a scientific or definitive answer either. I do have a FG pool and have "shocked" up to 25ppm once without any adverse affects, other than staining. This is supposedly due to metals in the water however I have my doubts since everyone who has tested my water says there aren't any metals. I haven't figured it out yet but it cannot be caused solely by the High FC level since I generally have to do an "ascorbic acid stain treatment" a few times each season and rarely have to shock. My pool color is the same as Waterbears, see his picture in the upper left hand corner of his post. I also know someone with a white pool and they use dichlor to shock their pool. No telling what level they've gone up to as I have seen numerous empty bags around after they opened. Back to your original question, I can't imagine a FC level of say 50ppm hurting the fiberglass. As an avid boater, I have used some pretty nasty and acidic stuff on my boat without any adverse effects. I would venture a guess that at some point, chlorine (or acid for that matter) could cause the gel coat to oxidize (develope a white haze on the top layer). What that point would be I haven't a clue. Let me stress that this is only a theory.

Dave

[reneep]

I have a 10K gal fiberglass pool and have fought staining for several years with weekly shocking. Now that I have discovered this forum, I realize that using 3" tabs has caused my CYA level to be extremely high, causing the need for more CL, causing more staining. Now in the process of drain/refill to lower CYA and begin a bleach only plan. Having said all of that, the finish on the pool does not seem to have been affected.

[waterbear]

. My pool color is the same as Waterbears, see his picture in the upper left hand corner of his post.

My pool is white, the blue color is just from the very clear water and the way the sun was that day.

I have beent trying to reseach this and can find nothing definitive on how high a chlorine level is safe for FG. San Juan pools (the manufacturer of my pool) does state in their maintenance manual that high sanitizer levels can damage the gelcoat but don't say how high is too high. I have also seen several times that FG doesn't require as high a FC level as vinyl or gunite because the coating is non reactive (this one doesn't make any sense to me since it is the water that needs sanitizing, not the pool shell) and I have also come across an interesting tidbit about calciium a few times. It seems the gelcoat has some metals in it's makup (cobalt?) and soft water can leach them out which is why calcium is recommended for FG at about 175 ppmto help prevent it in much the same way it prevents leaching the calium out of a plaster pool. Calcium is a metal and this does make sense chemically. This topic has been discussed in a different thread but I have run across this several more times. Can't prove it one way or the other, however!
I also ran across some info on fiberglass pipes and how they are recommended for caustic chemicals including sodium hypochorite because they are non reactive. Then I ran across info on fiberglass patio furniture that is not warrentied against damage from chlorine.
Very conflicting info!