UnknownStain - Fiberglass Pool

Hi All,

My pool has been covered for about 2 weeks (solar cover) because weather and temp. has not been ideal swimming weather. I have been testing the water every-other-day, though, and keeping up with the water. Today, I rolled off the cover and noticed 5 stains at the bottom. Each stain is round and very large - ranging from 4"-6". 3 are in the shallow end and 2 are in the deep end. I have a 16x33 IG fiberglass pool that was installed this June - 13,500G. Fiberglass is light blue. The stain appears as light brown - it's almost like a grease stain bleeding through! If it's sunny out, you can't really see it, but if it's cloudy, you can see it pretty well if you look for them.

Since installation, I've been using Cl pucks. I'm aware of the CYA issue - but current levels are okay, so I haven't switched yet to bleach. Only during the past 2 weeks, the Ph levels dropped a bit, so I added some pool-store PH+ (bought the Soda Ash before I knew Borax would be ok). Did this about 4 times this past week - adding about 12 oz each time. Right after installation, I did put CYA in. And, I did shock once in early July using cal-hypo. Have not shocked since. Water has been crystal clear and have had no water issues.


A recent test done today:

Cl: 6 (Consistent between 3-6 all summer)
FC: 6 (Never ever test positive for CC)
CYA: 50
Alk: 90 (conistent over the summer)
Ph: 7.3 (since installation, was very stable at 7.5. Since covering 2 weeks ago during non-swim times, pool seems in need of PH+ sometimes.)

I'm probably going to call the fiberglass manufacturer on Monday, but thought I'd post this to see if any fiberglass owners ever experienced this issue. Seems like the fiberglass somehow got stained. And, the only thing differently done in the last 2 weeks was the add of Soda Ash and covering the pool when not in use.


I would have posted a picture, but the camera is not picking up the stain. I am running a heat pump, too and keeping the pool at 86.

It may be a metal stain. If you have any ph down, or some vitamin C tablets, you can try it on the stain. Crush the vitamin C tablets up and rub it onto the stain. IF the stain goes away, it is a metal stain. You can also try some ph down in a sock and rub it on the stain. Your fiberglass pool will stain from metals very easily. Adding the soda ash could have reacted with the chlorine in the water and dropped some metals out of solution. If it is a metal stain, you will need to get some metal sequesterer, lower the ph down to 7.2 and add at least as much as it says on the bottle, more is better than not enough. IF the stain is not removed after a few days, then you can do a stain treatment. Let me know how you do, and feel free to ask any questions you may have.

Hi Marie,

Thanks for your reply! Here's a dumb question, if the stain is at the bottom, how do you rub the crushed-up Vitamin C on it? Is there a technique to get the liquid onto the stain?

Same questions with the Ph-? Is there a technique for applying to the bottom of the pool?

The stain in the least shallow part of the water is at about 4' deep.

Is one test easier to perform under water than the other?

Thanks again!
Marc

You can tie the sock onto the skimmer pole and let it sit on the stain. You can put a couple of crushed vitamin C tablets in a thin sock or pantyhose, and tie it on the skimmer pole and let it sit on the stain. If you want to see if the stain is organic, then you can crush a trichlor puck up and do the same. If the stain is llifted by the chlorine tablet, then the stain is organic, and will lighten with high levels of chlorine. If the stain is from metals, then you will need the sequesterer or a stain treatment. Sometimes if the metal stain is new, you can lift it off with just the sequesterer. In my opinion it is a metal stain, because it fits with everything you have posted - and you have a fiberglass pool. You can read back through the metals forum and see that it is very common, and can be taken care of:) Let me know how the tests go, and I can help you further.

A thousand thanks, Marie. I'll try to do the test today, but I need to do it when it's not sunny and, as you know, it's a beautiful day here in the tri-state area. So may have to wait a bit. Pool closes in 2 weeks, so I need to get it done! Hard to believe the the "gel" from a Vitamin C tab will remain in a sock, but I'll give it a try!

Do you have a San Juan pool ? I was wondering because the 16x33 is sort of uncommon (at least the 33 is) and we both have the same size. Mine's an Atlantic.

Anyone, I've been reading the manufacturer site and it says don't use a sequester (not even sure what that is). They recommend Jack's or Metal Magic. See: http://www.sanjuanpools.com/maintenance.html

Reading about Jack's, it says it's "heavier" than water, so I guess it floats down to the stain.

In any event, looks like it's treatable, which is great news.

Again, thanks!

Hey Skill,
Just FYI, Marie (and WaterBear & ChemGeek & more- Thanks to you all!) have posted excellent details on those products, how they work, their compatibility with fiberglass, and the whole chelating/sequestering issue. You'll find tons of info by searching for Fiberglass Stains or those product names. I would post a link, but there are easily a dozen threads I've found invaluable. Best of luck tackling this before closing!

Sorry, but I never saw a vitamin c gel tablet. I have only had the solid form, so I don't know how you would get the gel on the stain without going in and rubbing it on by hand. Yes, it is a beautiful day, and I was just out getting the pool ready for closing:( I hate closing - it means it's the end of the summer. Anyway, I would just get the sequesterer for now, or not even do anything - I have closed with stains, and opened stain free. I think it may be that the the ph gets low over the winter, and as the chlorine gets low, the stains lift off. So in my experience, I wouldn't worry much about it, because you don't need to put any extra money in at the end of the season, and the stain treatments make it hard to rebalance the water - so if you want to close in the next two weeks, I wouldn't worry about the stain for now. If it is bothering you, you can do the sequesterer - I would recommend metal magic, because it is supposed to turn any metals in the water to salts, so they can be filtered out. Jack's magic is a very good product also, but it just sequesters the metals, unless you use the stain treatment which is ascorbic acid, and that will take a while to rebalance after the treatment. You also can't shock the pool for 2 weeks after the treatment, so you won't be able to close right away. Let me know if you have any other questions.

I'm taking your advice - will probably treat next year. Again, thanks for your help.

Pool company has stood me up the last 2 weeks, so the pool is still uncovered. So, I took the above advice. Crushed up 8 Vitamin C tablets in a pantyhose, attached it to my skimmer pole with duct tape, and rubbed the pantyhose on the stains. No more stains ! Also, tried the Vitamin C in my stainless steel sink and it removed some of the iron stains there too.

Thanks for the great advice!

Just wanted to add to the thread, one of the reasons that you probably got the stains in the first place is that when you added the ph+ your chlorine may have been high. High ph + high chlorine will make any metal that is in the water fall out onto the pool surface. I don't know why your pool manufacturer would not endorse a sequesterer, but will endorse metal magic or Jack's Magic - the Jack's Magic pink stuff is a sequesterer! In any case, check your trichlor tabs to see if they have copper in them - some of the trichlor is adding copper as an agelcide right into the tablets. Fiberglass pools are very suseptable to staining. I run my pool at a ph of no higher than 7.4, and keep the chlorine at the low end of the "best guess" chart. I also keep a sequesterer in the water at all times. One way to handle stains that pop out is to take the ph down to 7.0 - 7.2 and add a sequesterer - this will sometimes lift a stain that is new. If the stain gets more embedded, then a treatment with ascorbic acid (vitamin c) will take them off. I hope you got your pool closed for the winter, and next year when you open I can help you keep your pool stain free:) I can't waint till the next swim season:)

I opened my pool 12 days ago. Water balance looked pretty good. CYA held all winter at 55. Shocked the pool to about 15 and have not added bleach at all since opening and Cl is still staying at about 10. But, I noticed my pool is pretty stained - no longer just some spots. The stains are light though, only visible after the sun goes down, but there's a ton of them covering large areas.

I bought some of the Proteam Metal Magic product over the winter and wanted to use it tonight, but the label calls for the Ph being at least 7.5. So, I dumped some soda ash in to raise the Ph (it is currently 7.2) and was going to use tomorrow. Now, I'm not so sure if I should after re-reading some of your prior posts where you've indicated that the Ph should be low before using a sequester.

I'm not that worried because I know I can always throw a pound of ascorbic acid which will take care of the stains. But, maybe the Metal Magic will work without the acid and keep the stains away.

But, do you recommend using the Metal Magic at 7.5 (as the label recommends) or lower?

Go ahead and put the proteam metal magic in - it probably says to use it at a ph of 7.5 because it is very acidic itself, and will bring your ph down on it's own. I usually say that you should put your ph at 7.2 with sequestering agent because you want the water to be acidic to lift the stains. Since you have the metal magic I would try it first. If it doesn't lift the stain, then you can do the ascorbic acid - but give it a couple of days first, and if it doesn't bring the ph down to 7.0 or 7.2, then add a little muriatic acid, and keep the filter running 24/7. Good luck, and let me know how it goes.

Ok - wanted to get back with my results. I put the Proteam Metal Magic in Sunday night and was travelling until today. Pump ran 24/7 since Sunday with the pool covered with the solar cover.

Tonight, when I uncovered, all stains were gone. I really could not believe it. Marie - you were right on the Ph. It lowered it to 6.8 - my pool has never been that low. Lowered the TA only by 10 - so I'm at 100. Threw about 2 lbs of borax in and will test again tomorrow.

Thanks again for all your help - pool is immaculate once again.

Oh - one more question. I was reading that the magic eraser works great. All my grout below the water line is sparkling white, and above the waterline is pretty grungy. I suspect the chlorine keeps it white below the waterline. Here's an idea for the lazy: Instead of using the eraser, I wonder if I could "overfill the pool" to above the groutline, then shock to see if the grout would come clean. Then drain back to normal water level. THoughts?

I am so happy that your pool is clear of stains!!! Yes, you can raise the water level, and keep the chlorine level high - it will clean the grout, but it will take a while. I love to hear the results of what works and doesn't work. This year I opened my pool to an emerald pond, with strings of green algae:eek: My husband wanted to drain and refill, but I knew it could be cleaned up becaue of the information I got reading this forum. That was last Friday evening. I checked ph, and for the first time on opening, my ph was above 8. It is usually below 7. You just never know what a pool will do:rolleyes: So I added proteam metal magic - and lots and lots, and lots of bleach. By Sunday the pool was blue - but extremely cloudy. I don't know if it was just dead algae - I think the proteam may have made it cloudy too - it is supposed to turn metals into salts so they can be filtered out (I am not sure that I believe it yet) but there were very small particals that when I vacuumed seemed to go right through the filter. I used some floccuant, and let the water settle overnight. I vacuumed to waste, which made me have to add more (well) water, and I continued to keep my chorine level above 20 with a very low cya. I now have crystal clear water, and no stains - which with such a high level of chlorine for so long was amazing. I did however keep my ph at about 7, with my alkalinity at 100. I wish I would have taken a picture to post what the pool looked like when I opened and how it looked as the bleach cleaned it up. It is hard to believe sometimes, but pictures speak a thousand words. I tested three times a day bringing the level up to 20 each time. Even though I had no combined chlorine showing after three days- the chlorine was being used up overnight, so I continued to keep the level at 20 until it was not going down overnight, which turned out to be 3 days more. And just as a note, I closed my pool the same way as I have the last 4 years, and the last three I opened to almost clear water with a lot of dirt on the bottom. This year we had a lot of rain, my pool actually overflowed, and then a lot of hot sunny days before opening. My guess it that the cover was wet, grew algae and it seeped into the pool and took off - it really ran away with itself:( So, as I said, you never know exactly what your pool will do, and it is good to share info, so we can help each other.:)