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Thread: Need advice from experienced owners of Fiberglass Pool with SWG!!

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    Need advice from experienced owners of Fiberglass Pool with SWG!!

    Hello All -
    I've had a fiberglass pool (with gelcoat) and a SWG for about five months. This site has been invaluable in getting started and my water looks good. I posted a few months ago when I just started, but I'm getting so much conflicting information!!!

    Typical test results -

    FC 1-4 (High in the a.m., low in the p.m., but see my CYA snafu below. It's gone five months with probably zero CYA, so hope that's not going to cause a long term issue)
    TA is currently 80-90 - I've learned to adjust that upwards with banking soda as needed
    PH 7.8-8 - this creeps up constantly - natural result of the SWG? Would my non-existent CYA up to this point result constantly rising PH?
    CYA - zero when I tested, but added conditioner (my bad - somehow I thought sodium bisulfate was CYA, but I found my error and added conditioner today! Will shoot for around 60 CYA level)
    Calcium Hardness -500-525
    Salt ~3600 -pool manual recommends around 3200



    Here a few conflicts I'm trying to sort through...

    1) dry sodium bisulfate or liquid muriatic acid to lower PH? - Viking pool manual recommends sodium bisulfate. SWG manual says in areas with hard water (my calcium hardness runs around 500) NEVER use sodium bisulfate. Local pool store says never use muriatic in a fiberglass pool, but another local pool "professional" says never use sodium bisulfate. Who's right? I am having to add one or the other weekly to keep the PH around 7.6. Sodium bisulfate is certainly easier to handle, but don't want to damage fiberglass or burn out SWG prematurely.

    2) Total Alkalinity -pool manual says keep it between 125-150, but forum says maybe 60-80. Is there a chance I will damage the fiberglass by going with the lower number?

    3) Free chlorine - fiberglass manual says around 1-2 ppm is good-but i see recommendations of up to 4ppm. What's best for the fiberglass?

    4) metal staining. Just recently appeared a few quarter-sized pale rust-colored stains in deep end. Threw some ascorbic acid tablet on the and they seemed to resolve, so iron? What the best sequestrant for fiberglass with a SWG? I have a natural rock water feature that may be added some extra mineral and/or metals as well.

    5) Would I benefit by adding Borax?

    6) What can I do to prevent scaling/calcium buildup on the fiberglass?

    7) Has anyone tried Marine wax above the water line to keep the fiberglass protected and shiny? What has been your experience?

    Thanks so much - I appreciate experienced input on any or all of my questions!
    12,000 gallon in-ground Viking Fiji fiberglass installed Dec 2016, Jandy TruClear SWG, variable speed Jandy 2.7 HP pump 4 cartridge filter, inland Southern California

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    Mod Squad YippeeSkippy's Avatar
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    Re: Need advice from experienced owners of Fiberglass Pool with SWG!!

    Quote Originally Posted by Myfiji View Post
    Typical test results -

    FC 1-4 (High in the a.m., low in the p.m., but see my CYA snafu below. It's gone five months with probably zero CYA, so hope that's not going to cause a long term issue) Other than offering up sacrificial chlorine to the Sun Gods, nah, it won't have hurt anything. Assuming your pool is still algae free?

    TA is currently 80-90 - I've learned to adjust that upwards with banking soda as needed Raising your TA is encouraging your pH to go high also. Stop that. See how your pH stabilizes if you keep the TA around 60-70.

    PH 7.8-8 - this creeps up constantly - natural result of the SWG? Would my non-existent CYA up to this point result constantly rising PH? My pH doesn't tend to rise, but others with SWG do. Take your pH down to 7.2 with MA, and that will also have the benefit of bringing your TA down a bit also.
    See this--> Pool School - Lower Total Alkalinity

    CYA - zero when I tested, but added conditioner (my bad - somehow I thought sodium bisulfate was CYA, but I found my error and added conditioner today! Will shoot for around 60 CYA level) Ok, good that you figured that out. Stop using bisulfate... it leaves suphites (or is it sulfites? I forget!) in the water which you don't want. Use MA

    Calcium Hardness -500-525 Keeping your pH on the lower end of the suggested range will help avoid problems due to high CH. If you know you're going to get a bellywasher of a rain storm, try to get as much of that in the pool as you can. Some folks even rig up systems so that their roof downspouts direct into the pool when they have hard water.

    Salt ~3600 -pool manual recommends around 3200 If your SWG is happy and making chlorine.... don't change a thing.

    Here a few conflicts I'm trying to sort through...

    1) dry sodium bisulfate or liquid muriatic acid to lower PH? - Viking pool manual recommends sodium bisulfate. SWG manual says in areas with hard water (my calcium hardness runs around 500) NEVER use sodium bisulfate. Local pool store says never use muriatic in a fiberglass pool, but another local pool "professional" says never use sodium bisulfate. Who's right? I am having to add one or the other weekly to keep the PH around 7.6. Sodium bisulfate is certainly easier to handle, but don't want to damage fiberglass or burn out SWG prematurely.MA is fine.

    2) Total Alkalinity -pool manual says keep it between 125-150, but forum says maybe 60-80. Is there a chance I will damage the fiberglass by going with the lower number? Never heard of any damage.

    3) Free chlorine - fiberglass manual says around 1-2 ppm is good-but i see recommendations of up to 4ppm. What's best for the fiberglass? 1-3ppm of FC in a pool without any CYA is *far* harsher than 8ppm in a pool with CYA. Use this guide: FC/CYA Chart

    4) metal staining. Just recently appeared a few quarter-sized pale rust-colored stains in deep end. Threw some ascorbic acid tablet on the and they seemed to resolve, so iron? What the best sequestrant for fiberglass with a SWG? I have a natural rock water feature that may be added some extra mineral and/or metals as well. Can you seal this rock feature in some fashion? If you use the water feature often that is another reason your pH goes high. Scale that back and see if that helps.

    5) Would I benefit by adding Borax? You mean borates? I wouldn't until you understand pool chemistry better. Once you add them it makes tweaking your pH and TA harder. You only add them when everything has been perfect for a while.

    6) What can I do to prevent scaling/calcium buildup on the fiberglass? Keep your pH in range, even on the lower end of desired range.

    7) Has anyone tried Marine wax above the water line to keep the fiberglass protected and shiny? What has been your experience? I've used car wax without problem to keep water spots from looking messy. Its a job to put it on and buff it off the surface while keeping it out of the water. I've also used my hot tub surface cleaner with good results.

    Thanks so much - I appreciate experienced input on any or all of my questions!
    Did I hit all the points?? Just bring back any questions-

    Yippee
    Maddie :) 12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
    Skippy's Pool Cooler --> Skippy's New Fountain Our Build --> Our Pool Solved Our Sloping Yard

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    Re: Need advice from experienced owners of Fiberglass Pool with SWG!!

    Thank you very much for your reply! Nice pics of your pool by the way in the other thread!

    My water looks and feels fine - no algae issues whatsoever. I think the only consensus I've found so far is to keep the PH on the low end.

    I'm still torn on the correct TA level to maintain. I consulted a local family-owned pool store owner today and he said the reason for high TA in a fiberglass pool is that it keeps more elasticity in the fibers, which helps prevent delamination (and he wasn't selling me a product for this as he acknowledged baking soda would do the trick). Wish I could see some science or historical information specific to TA and the longevity of fiberglass, but I don't think there is as much to pull from given fiberglass pools are still a minority.

    I have actually pondered if there's a way to seal the rock for our water feature - will have to look into that some more. Thanks for the suggestion! I'll also check out hot tub surface cleaner!

    Appreciate all you help!
    12,000 gallon in-ground Viking Fiji fiberglass installed Dec 2016, Jandy TruClear SWG, variable speed Jandy 2.7 HP pump 4 cartridge filter, inland Southern California

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    Pyrodav's Avatar
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    Re: Need advice from experienced owners of Fiberglass Pool with SWG!!

    I installed a Viking last year also. The gel coat is in contact with the water. Im not sure how the fibers would be affected? I would be interested in learning more about that. My TA is around 80-90. Shooting for 80.
    7000k Viking fiberglass Bermuda, Sand filter w/glass, Pentair SuperfloVS, Pentair IC20 swg
    Raypak 106k, Dolphin s-200, Taylor k-2006c, Taylor k-1766, Speedstir, Little Giant cover pump.

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    Re: Need advice from experienced owners of Fiberglass Pool with SWG!!

    Pool.jpgWe have the Fiji Viking -love the way it turned out. Does your PH constantly creep up too? I've had my TA low and high, PH creeps up either way. If there's any truth to the connection between high TA and the "elasticity" of the fiberglass fibers, then I'd opt to do what is best for the pool shell. My pool manual and SWG manual are in direct conflict for chemical balance recommendations, but I'd rather replace the salt cell than have to refinish the pool shell!
    12,000 gallon in-ground Viking Fiji fiberglass installed Dec 2016, Jandy TruClear SWG, variable speed Jandy 2.7 HP pump 4 cartridge filter, inland Southern California

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