Perimeter Stain

I have a brownish yellow stain around the perimeter of my pool.
40,000 gallon
vinyl liner - L shape
about 6 years old

There was a faint stain the end of last season- I tried letting the chlorine level drop and added stain remover at end of season- it disappeared
Same stain early this seaon- tried the same thing and the stain went away
Now a few weeks later it is back and worse then ever.

I am not sure if it is metals - in reading the posts I think it may be and I need to try to suspend it??

I was told at the pool store(I know that is a no no so that is why I am asking here) That it is metal because this season about 2 days after using stain remover my water showed high for copper. They said that it takes a week for it to work its way out of the water?
Then when the stain reappeared- it showed no metals at all when tested- They said the metals were no longer showing in the test because they were not in my water- but back in my liner

Is this so?

I have always kept my alkalinity- PH and chlorine in correct ranges
Last year I found this site and switched to chorline- especially for shocking because it does not cloud - so nice

This is driving me crazy- and I find it hard to keep my chlorine level high- it keeps dropping but CYA is good.

Any ideas on who to listen to- what to read- or what else to test?

Thank you for any help that you can give me.

Do you know where the copper is coming from? The reason your stain came back after the stain treatment is because you didn't put in a sequestering agent to keep the metals in suspension. If the metals go back into the water, they need the sequestering agent to hold them in the water, if there isn't enough of it, the high chlorine levels will react with the metal and they will fall out of suspension and land on the surface of the pool. I asked where the metals came from, because copper is in a lot of the chemicals you buy at the pool store now - even in a lot of trchlor pucks. If you think the metals are coming in from your fill water, then you will always have to make sure that you have enough of a sequestering agent in your water. I hope this helps, feel free to ask any questions you may have.

Thank you for your help.
I will check my tablets- I do use tablets in the chlorinator
I use baking soda to raise the Alk and Soda ash to raise the PH.
Shock with bleach.
I did put in a chemical called Bug out-
Will copper be listed on the bottle- or will it be listed as some other name?

Do you know if the copper could be leaching from an old hose- or somewhere in the filter- any ideas how to check them? How can I can tell if the copper is coming from our city water?

Any ideas on this will help- and thank you again.

Pam

I am pretty sure the copper would be on the label of "bug out" and the chlorine pucks, Other than that I don't know how to find out where the copper is coming from. I don't know where the metals come from in my pool- my water always test no metals, but I get stains, so I can't help you there. Maybe someone else knows more on finding the cause of it? But I do know that they can be controlled by keeping a sequestering agent in the water, adding the fill water through the filter, and keeping the ph on the low side. Post your chemical numbers (fc, cc, tc, alk, ph, cal,cya) and maybe I can see if anything is off.

Do you have a brand of sequestering agent that you recommend? How do you add fill water through the filter? (I have an above ground pool w/ sand filter.)

I have used metal free, sequasol & Jacks Magic. They are all good. To add the fill water through the filter, you put your hose in the skimmer (with a trichlor puck). The water will hit the puck, and flow right into the filter before it is returned to the pool, so it could help the metal stain the filter instead of the pool. The sequestering agent should keep the metal in suspension - make sure you add at least enough of what the bottle says, because more won't hurt anything, but not enough will leave some metal free to fall onto the liner.

I thought the sequestering agent put the metal in suspension so it can be filtered out. So, if you raise CL too soon, the metal falls on the liner and stains, but if you wait a week or so, the stuff filters out of the water. No?

I thought they would be filtered out too, but I am told that they do not get filtered out - they just stay in suspension. But I have had my water tested after the treatments and they test as no metals, so I don't really know. I do know that if I keep my water treated with the sequestering agent I don't get the stains back. I keep reading all I can about the metals in swimming pools, but there doesn't seem to be a way to filter the metals out, except by doing it a way that Pool Doc says - but it involves careful control of ph and bleach to get the metals to fall out on the filter. I don't have a complete understanding of it yet. If anyone out there can chime in and give a better answer, please do!

Don't know about a better answer, but I do know that when we had the well pump filters breached while filling, our pool turned chocolate brown - I mean really brown. We made the mistake of putting the bleach in the water (not knowing that the filters had been breached) so when we put the first sequestering agent in the NASTY stuff made a 2" wide ring of crap around the perimeter - this brand of stuff apparently had the phosphonic(sp?) acid along with "soy protein" or some such junk in there as it was claimed to help "soften" the water. Horse Pucky - it just made a mess around the edges of the pool. The Metal Myte (good stuff) sequestering agent went in and we ran a cartridge filter and a small sand filter 24/7, cleaning and backwashing often - there was sticky thick goop on the cartridge filter and brown ooze came out of the sand filter when backwashed. We had to use a LOT of the Metal Myte - at least 4-5 bottles over a week. The water is now clear and does not test for metals anymore. There is a thick puddle of brownish orange residue on the ground near the edge of the woods where we cleaned cartridges and backwashed the old sand filter to attest to something being removed from the pool. My guess is if it puts it in suspension, it must coat the iron/metal particles and they can then "stick" in the filter better? Kind of like what the clarifiers do, make it clump? It took something out of the pool.

CHEMISTY NERD STUFF ALERT! NOT FOR YUPPIES OR THE WEAK OF HEART!:rolleyes:

Quote:

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Originally Posted by mbar

I thought they would be filtered out too, but I am told that they do not get filtered out - they just stay in suspension.
Right Marie!, They are still in the water but in a 'chelated' form that keeps them from reacting with other chemicals like the chlorine or falling out of solution as stains. That is why it is important to keep up the maintenance doses of sequesterants if you have a metal problem.
But I have had my water tested after the treatments and they test as no metals, so I don't really know.
The metal ions are "seqeustered" (from dictionary.com)
se·ques·ter
v. se·ques·tered, se·ques·ter·ing, se·ques·ters
v. tr.

1. To cause to withdraw into seclusion.
2. To remove or set apart; segregate. See Synonyms at isolate.

The metal ions are, in effect, 'set apart' or inactivated by a process called 'chelation'

once again from dictonary.com
Chemistry. To combine (a metal ion) with a chemical compound to form a ring.
This ring structure means that there are no reactive points that can be affected by other chemicals in the water as long as the metal stays in this ring structure.
This is an oversimplification but you really do have a good understanding of the process and are the 'metal guru' of the forum!;)
Practical knowledge is MUCH MORE useful than the theoretical and you have that down!
I do know that if I keep my water treated with the sequestering agent I don't get the stains back. I keep reading all I can about the metals in swimming pools, but there doesn't seem to be a way to filter the metals out, except by doing it a way that Pool Doc says - but it involves careful control of ph and bleach to get the metals to fall out on the filter.
You are causing the metals to drop out of the ring structure and then fall out as stain on the filter by carefully controlling the parameters that break the chelation of the metal in a controlled way. It is tricky and doesn't always work right. PoolDoc understands this process much better than I do!
I don't have a complete understanding of it yet. If anyone out there can chime in and give a better answer, please do!

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Hope I explained it a bit!:)
As a side note that might help, I have used copper in fish tanks to treat certain parasites. Copper is available as chelated or not. If you use chelated copper it doesn't show up on a test until it breaks away from the chelation. I have seen tanks that all of a sudden would test at high levels of copper a month or more after treating with chelated copper and showed practically no copper from the time of treatment until then. If the treatment with the chelated copper is overdosed it can prove deadly to some of the tank livestock when it becomes active and the copper levels shoot up and overdosing is easy because the copper doesn't show up in full concentration on testing in chelated form. I know that many copper based swimming pool algecides use chelated copper which WILL eventually cause staining down the line for the same reason.

Thanks Waterbear! Last year I played around a lot with the water in my pool to see what would stain, and what wouldn't - I ran high ph with low chlorine, ran high ph with high chlorine, ran low ph with high chlorine, and low ph with low chlorine. I started the year with low cya, so I was able to do these tests along during the time I was raising my cya with trichlor pucks. I used very little sequestering agent, to see what happened after ascorbic acid treatments, verses using just the sequestering agent with low ph to take the stain away. Now this year I am trying to do the whole summer without stains. So far, I have been able to open it and be almost stain free - I noticed a little stain forming on my seats, so I brought the ph down and added more sequestering agent - the stains lightened up. I put 3 bottles of Sequasol in so far. My pool is perfectly clear, and stain free (yeah) This year my cya didn't disappear, so I started with a cya of 35 - I am using almost all bleach - I do put a puck in the skimmer whenever I add water, and whenever I take my chlorine high. So far so good, but I am not counting my chickens, because in past experiments those nasty little brown stains came back to taunt me! I have some other theory's too - but nothing I can say for sure. I will keep trying and hopefully we can all learn from each other - that's why it is so great when others post their results here. Thanks again Evan, you really explain the chemistry in a way I can understand it.

Marie,
Very glad to hear it was helpful!:)