Yellow stains on liner

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
I have read some other posts pertaining to this, but still a bit confused on what to do. I have a bunch of yellow staining on my pool liner. It looks a lot like it would if you had mustard algae but when you brush, it doesn't come off. I have been SLAM'ing for the past 10 days or so, and the staining seems to be much worse. I just noticed at the bottom near the drain, it is almost a swirl-like pattern everywhere except about 6" around the drain. I am attaching some photos, but the camera really doesn't capture it very well.

The only thing I have changed, is I put in one of those "skim-a-round" skimmer baskets to see if I could get a bit more flow to my only skimmer, and to get it to work, I had to turn down pump flow of drain and move more pump to skimmer. Also, I ordered my HDX liquid chlorine from a different Home Depot than I normally do, and when it was delivered, the jugs were very dusty, so could expired Chlorine cause this? It seemed a bit more yellow in color when I poured it in.

If I need to test for metals, can I do this myself, or does it have to be at the pool store, which is closed as non-essential due to Covid. Thanks.
 

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Texas Splash

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You're right about the photos. A bit hard to tell. I wouldn't think the HDX chlorine has anything to do with it. Even if it was old or stored in the heat, it should just be weaker. When I hear yellowing I think of two things - pollen or copper. Iron usually shows-up brownish, but you can check for that too. Can you get to any of those stains by hand? If so, rub some Vitamin C tablets on an area and see what that does (iron). If nothing, try some dry acid in a thin sock or nylon if you have any (for copper). Last, just rub a tablet around for a short bit (organic). With the acid and tablet, keep them moving a little as to not damage the liner by sitting in one spot too long. Those three tests should help you pinpoint what is causing the yellowing. Let us know how it turns out.
 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
I live in Atlanta and we have been seeing pollen counts close to 10,000, but if it were pollen, could that actually stain the liner so that even brushing it would have no effect?

When you say "rub a tablet around for a short bit", what kind of tablet are you talking about?

Re: the vitamin C tablets, are just talking about the chewable tablets people take?
 

Texas Splash

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When you say "rub a tablet around for a short bit", what kind of tablet are you talking about?
A chlorine tablet (puck) if you have one.

he vitamin C tablets, are just talking about the chewable tablets people take?
Yes. Just the plain of tabs you get from the pharmacy section.
 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
Not sure about the chemistry explanation, but the first test I tried was the Vitamin C. I did not have pure C, so I used an "Airborne" tablet which is Vit C and some other stuff like Zinc, magnesium, manganese, etc... I dropped it in and used a pole to slide it around the bottom and it took the yellow off completely. So does that mean I have too much iron in water? What now?
 

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Texas Splash

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So does that mean I have too much iron in water? What now?
Yes, Vitamin C removes iron. So here are some things to consider so you can take action:
- Iron comes from somewhere. Either your city water or well. It would be good for you to know for future reference. But once iron is in the water, the only way to truly remove it is by changing all or some of that water with fresh water.
- If changing water is not an option, then you have to control it. This means carefully balancing the FC with your current CYA. For that, always go to the FC/CYA Chart.
- Next is pH. An elevated pH makes the iron precipitate out of the water and try to bond to surfaces. So try to keep the pH controlled - maybe in the mid-7s if you can.
- Use a good sequestrant. Those products help to "bind" the iron and keep it soluble in the water so it can't stain. But sequestrants wear-off over time, so you have to add more periodically.

You also want to avoid algae because if you ever get algae, you'll have to increase the FC level considerbally which will make the iron staining potentially worse. This may seem like a lot of info, but read it tonight, then again tomorrow and just try to take in a little each time. In addition, below are a couple very good articles you may want to read about stains and a process commonly used to remove large area stains.

 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
Should I finish my slam, then get the rest of the readings perfect before trying to get rid of stain? Also, will the sequestering agent remove the stains or just react with the iron floating around in the water? Just trying to avoid the immense hassle of doing the ascorbic acid routine. Seems like a a pain! :-(

I lose about 2 ppm FC daily in summer so a couple times a season I forget to add bleach or I run out and takes couple days to get more and that darn mustard algae comes back quick so I have to slam again. The pool was really bad over winter and ph was well above 8 and zero CYA so maybe that combined with recent slam is causing this issue.
 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
Ok, I re-read everything several times. If I understand correctly, I need to remove the stains using the Ascorbic Acid, then treat the water itself with a Metal Free product. I have been looking at different metal free products, and found one where the dosage indicates it would be more cost effective - Natural Chemistry Metal Free, the dose is 1 liter per 20,000 gal and it is $17/liter, whereas the Pro Team Metal Magic is 1 liter per 10,000 gal, and $23/qt. Are you familiar with the product from Natural Chemistry, they also make an Ascorbic Acid product. Of course, the reviews on the Metal Magic are all really great.

Here are my numbers this AM:

FC: 6.5
TA: 50
pH 7.4? (see photo, I am having trouble figuring out the color chart - let me know what you think it is)
CYA 40

So the order of operations is - wait for my FC level to drop to zero or close to it, then do the Ascorbic Acid, then do the Metal Free? Only unknown is what you think my pH is and whether I need to do anything for that before I start. During this whole process, do I need to do any brushing or vacuuming?
 

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Texas Splash

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I'm not personally familiar with the Natural Chemistry. I've seen them posted here before, so I know there are threads about that brand. ProTeam's Metal Magic and Jack's Magic the Pink Stuff (regular), the Blue Stuff (fresh plaster), and the Purple Stuff (SWG) are some of the top sequestrants. There are of course other brands with similar products, some of which are noticeably less expensive. Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective, that's the key.

Your pH looks orange to me - low enough. You have the correct order (drop FC > AA treatment > sequestrant). You didn't mention a Polyquat 60 algecide, but you may want to add that once you drop the FC to avoid algae. Remember, if you get algae, the whole process of stains and AA treatment could potentially start again. So for pools with elevated levels of iron/copper, do the SLAM first (if needed) or avoid algae at all costs. Then do the AA treatment. Hope that helps.
 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
Regarding the algicide, I found "BioGuard Algae All 60" at Amazon, but it says: Product Information: 60% Polyquat pH 6.5. Does this mean it is diluted, or is the 60% normal?
 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
So I ordered all the stuff to resolve the iron issue, and while waiting for it to arrive, I went to pool store to have them test for metals, and they found no iron, copper or any metals. They even ran the test 2x. The guy said that the staining could be tannins from leaves that sat at the bottom of pool for a while. Since Ascorbic Acid removes stain completely, but there is no metals in the water, what would you suggest, could it be tannins? I am planning to lower FC to zero, add Polyquat 60, and add Ascorbic Acid to remove the stains, but is that all I need to do, and just return the Metal Free I bought? Pool guy gave me a couple iron test strips and said that after I add the Ascorbic Acid, to test for iron again to be sure. Thoughts appreciated.
 

Texas Splash

Mod Squad
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You should be able to see improvement from Tannin stains (organic) with a chlorine puck if rubbed on the stain for a short time. The fact that AA removed a stain right away tells us it's metal. Metals testing can be a bit expensive which is why we sometimes recommend having a water sample done by the pool store - just to see what they show for iron/copper. Unfortunately the accuracy of those tests is up in the air just like their other testing. In addition, chlorine in the water can interfere with metal testing, so sometimes it can be misleading. But if AA or Vitamin C tabs worked, it's metal.
 

JamesW

TFP Expert
Mar 2, 2011
18,444
I went to pool store to have them test for metals, and they found no iron, copper or any metals.
All water from natural sources has iron.

There's no such thing as a pool with no iron in the water.

Also, if most of the iron is in the stains, the amount left in the water can be below the testing limit.
 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
I have added ascorbic acid 4 times waiting 30 min between and all the yellow stains are completely gone. There is some white looking swirl stains only at bottom of deep end and I have tried to target my acid applications there but not really working. Can I let this circulate overnight before adding the metal free or just add it now and hope the white swirls go away? My FC was at 2 when I started which is maybe why it took more acid. Metal free now or wait til morning?
 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
Two things: I did not add the polyquat yet because we were not getting a lot of sun now and FC wasn’t going away very fast. But after re-reading process, this could take a while to get water balanced and FC levels holding. Is it ok to add now after I did the metal magic?

alsoI only bought 2 qts of metal magic and used it all so if yellow stains come back from here thru end of process I won’t have any to use. Should I just buy whatever pool store has or order more and wait a few days for shipping?
 

Texas Splash

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You can add the Poly-60 if you like. The last thing you want it an algae outbreak.

You can find other brands of sequestrants with similar products to the big names, some of which are noticeably less expensive. Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective. So I'd take a peek at the ingredients if you can.
 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
Quick question - the Metal Magic had been in pool overnight (12 hours), and when I tested this am, FC was 0, ph was 7, TA was 30, and water was cloudy (which I guess is a good thing). Should I wait until the sequestrant has been in pool for full 24 hours before bringing ph and TA up?
 

cholmes28

Well-known member
Jun 9, 2014
179
Marietta, GA
I guess the TFP site was down for a while today, so I just waiting the full 24 hours. I just added 105oz washing soda, then will retest in 30 mins or so, and see where I am at. So once I get the pH and TA good, then I can start to add my bleach to bring the FC up?