Fiberglass pool staining

[Peregrine133]

First year with new 13,600 gallon white fiberglass pool. Just finished battling colonel mustard algae for the second time. This time armed with more knowledge from TFP I'm hopeful I'm victorious. Near the end of the SLAM process I drained 250 gallons of water to access three PAL Treo side wall LED lights for cleaning. Each had a small amount of algae but I was determined to get all out. Refilled with city water. Last water test of SLAM using Taylor 2006 was
FC 23.5
CC 0
PH 7.2
TA 80
CYA 40-50 (started with 60 for SLAM)
CH 170
Salt 2600

Using Pool School calculator I added Salt, CH (1/3 of 60 ounces to start), Borax, and CYA (placed in sock in front of return). After each addition I brushed pool. About one hour after adding chemicals I noticed what appeared to be staining on bottom. Remembering reading about vitamin C tablets on TFP I placed some in a sock waded into pool and using foot rubbed bottom. Stain came off like an eraser on chalk board.
Reading more on stain removal using store products it stated lowering FC to zero. No way I thought after battling MA for the last three days.

Retested water this morning (about 12 hours after last test)
FC 24
CC 0
PH 7.4
TA 80
CYA 70? (I know it's too early to get accurate reading)
CH 180
Salt 3600

So what do I do now? I went from a beautiful sparkling pool after SLAM to stained bottom. It is a light staining however not the pretty white bottom after the SLAM.

 

[Texas Splash]

So now that you've successfully used the Vitamin C test, we know you have iron. Even though it's city water, unfortunately some water lines have iron in them and all you can do is manage it from there. You did the right thing though completing the SLAM Process. You have to pass all 3 SLAM Process criteria before addressing the stains. Now that the SLAM is over, you may need to consider looking at the Ascorbic Treatment to rid Pool of metal stains page. The use of Polyquat 60 should help during the period of low FC. Something else to consider …… cooler weather. While it may take another couple months or so, once your water temp drops below 60, algae will become more dormant which might be an excellent time to do the AA treatment if you're not in a big hurry.

 

[Peregrine133]

Thanks Texas. I just may wait to better understand the problem and allow more swim time before it gets too cold. Who knows, maybe they will go away on their own. I want to test the water at pool store for metals first. May contact the city as well to see if they have anything on the iron content in the water supply. Wait, that would be a liability to them I'm sure their test results are just fine.

 

[jmikeb]

i was thinking “stain removal party”. get a bunch of friends. give them socks with vit c tabs and GO!

 

[Peregrine133]

OK giving this some more thought. Once I follow the TFP AA proceedures i.e. lower PH add the AA, algaecide, sequestering agent and bring up the TC the iron is now encapsulated in the water. Since I have a sand filter over a period of time wouldn't the filter capture the encapsulated iron? If so, would changing out the sand help? The way I understand it otherwise I would forever need to keep adding sequestering agent?

 

[Texas Splash]

Since I have a sand filter over a period of time wouldn't the filter capture the encapsulated iron?

I don't think so. Sand isn't able to filter down to the micro level required like a polyfill or other similar products used to manually catch iron. Unless one purposefully increase FC and pH to make the iron precipitate out for manual filtration, it simply stays in a soluble solution in the water (with sequestrant) until that water is replaced. That's the unfortunate thing about iron or copper - once it's in …. it's in unless you change the water. Or in the case I noted above, manipulating the chemistry to make the iron jump-out of its soluble state and filter it within a polyfill-type product. If it were me, I'd probably just wait a couple more months for the water temps to drop so you can do an AA in colder water to avoid a potential algae nightmare. At the very least be able to maintain a much lower FC level.

 

[Peregrine133]

So your opinion on a product (bag) that you put into skimmer that is susposed to remove the sequestered iron? Also if I understand you once it is sequestered unless I let my PH and FC get too high I will not need to keep adding sequestering agent? If so, and I screw up and let chlorine drop and need to shock or slam will the metal be ok as long as I keep PH low? Sorry for questions but sometimes I need to hammer my head with info

 

[Texas Splash]

Products like scum balls and other metal capturing products (sorry forgot the names) that go in the skimmer have their limits. Much of what you are seeing in terms of staining depends on the amount of iron in the water. The comment about letting the FC and pH rise does not eliminate the need for sequestrant. Letting those tow items climb is used only in some cases as a method to get the iron to "come out" so that it can try to be manually filtered by the proper media. It's a bit risky for the novice and as you can imagine since the elevated FC and pH tend to increase the potential for staining. The #1 course of action is to exchange as much water as possible (trucked in if needed) to lower the iron content. For those who can't do that, it's a seasonal management process of keeping the FC on the lower end of the scale as allowable on the [FC/CYA][/FC/CYA]. PH should also be kept on the lower end of the 7s if possible. The lower FC and pH help to keep the iron in its soluble state. Along with the chemistry, the use of a sequestrant (i.e. Magic Jacks) is recommended which helps to contain the iron to keep it from staining any further. So as long as there is iron in the water (usually over 0.3 ppm), those processes will need to be followed.

 

[PoolguyinCT]

Products like scum balls and other metal capturing products (sorry forgot the names) that go in the skimmer have their limits. Much of what you are seeing in terms of staining depends on the amount of iron in the water. The comment about letting the FC and pH rise does not eliminate the need for sequestrant. Letting those tow items climb is used only in some cases as a method to get the iron to "come out" so that it can try to be manually filtered by the proper media. It's a bit risky for the novice and as you can imagine since the elevated FC and pH tend to increase the potential for staining. The #1 course of action is to exchange as much water as possible (trucked in if needed) to lower the iron content. For those who can't do that, it's a seasonal management process of keeping the FC on the lower end of the scale as allowable on the [FC/CYA][/FC/CYA]. PH should also be kept on the lower end of the 7s if possible. The lower FC and pH help to keep the iron in its soluble state. Along with the chemistry, the use of a sequestrant (i.e. Magic Jacks) is recommended which helps to contain the iron to keep it from staining any further. So as long as there is iron in the water (usually over 0.3 ppm), those processes will need to be followed.

The Scumball, mechanical captures sun lotion, pollen & insects. It is an effective product.

 

[Peregrine133]

Thanks Pat. Looks like pool ownership comes with a learning curve. Maybe in the second year will be enjoying more instead of worrying about screwing up. On side note been to Texas many times, it’s a big country. Spent four US Air Force years in the great state of OK and each year a little bit of Texas would blow up that way!