Drained pool, refilled, still have iron - where could it be from?

[poologant]

I had a non-stained pool for about 5 years but sadly I added Clorox Pool salt and I think (hope) that was the source of my iron.

I drained my pool and refilled but my iron stains came back within a day or two after getting the pool in balance. The stains are everywhere (fiberglass pool) more or less evenly stained.

I know the first question for me will be "does your fill water have iron?" I don't think so because I tested the water with a Hanna digital tester and with the pricey Taylor Midget Comparer. Both came back with a result that was zero (though the color compare on the Taylor test is subjective, so maybe trace amounts). To double check, I sent now sent my fill water (muncipal water via spigot not a well) to SimpleLabs/MyTapScore to be tested with their speciality iron specific test for ferric/ferrous iron. So, we'll see...

FYI, this is the same way I filled my pool five years ago and didn't have iron stains until last six months. Assuming the results come back with less than 0.1 ppm iron, I'm trying to figure out the iron source.

Here are my paranoid theories that might be the source:

• I was careless and didn't remove/clean my filters after draining the pool. Could enough iron have been left in the cartridge (4) filters? I did an AA treatment pre-drain, shouldn't be trapped in filters.
• There was about 8" of water left in the bottom on the pool plus what ever was in the underground lines (I would have thought that would be so diluted as to not matter)
• Could the pool robot (Dolphin CC Plus) be rusting (I can't see any signs of this)
• Could the pool pump be rusting - it is only 5 years old - Hayward Tristar VS
• I have two small rust holes forming in concrete but I don't have a rust trail going into the pool - plus the stains came back really fast after the refill.
• Pool chemicals - here's what I used to balance: FC-Walmart Pool Essentials Bleach 10%, CH-PuriTech Calcium Hardness Increaser, TA-Arm Hammer Baking Soda, Salt-Diamond Crystals Solar Naturals - Finally, HDX Muriatic Acid to control Ph

Since I still have iron in the pool AND since every method I have tried to filter the iron out of the existing water has failed, I going to have to drain (again!!) and refill. I'm quite paranoid now that I'll still have iron stains.

Are any of my theories plausible sources of continued iron stains?

 

[mknauss]

None of those items listed would add iron to your pool water. Fill water is your most likely source of iron.

Did you remove the stains from the pool surface using ascorbic acid prior to draining? You have to get the iron in solution to be able to remove it by draining.

 

[mgtfp]

You assumed that you initially got the iron in via Chlorox salt. Could the same have happened again after the refill with that different brand if salt that you used? Do you have some salt left that you could dissolve in distilled water and test for iron?

 

[mgtfp]

Did you remove the stains from the pool surface using ascorbic acid prior to draining?

Sounds like it:

I did an AA treatment pre-drain, shouldn't be trapped in filters.

 

[mknauss]

Then if done correctly, the fill water has iron in it. Significant amounts.

 

[YippeeSkippy]

 

[Orion7319]

View attachment 417482

Yeah we don’t really have a lot of iron in the water on this area. We do have a lot of houses with copper pipes, older ones with galvanized pipes. Our soil is red clay with a lot of iron. My pool steps need regular treatment with vitamin C because runoff leaves red mud on them.

 

[poologant]

Did you remove the stains from the pool surface using ascorbic acid prior to draining?

I did and the pool was completely free of any visible stains.

None of those items listed would add iron to your pool water. Fill water is your most likely source of iron.

I didn't think so either, but now I'm worried after a failed drain. Fill water test from lab due soon. My test didn't show iron but not sure they were good enough.

 

[poologant]

Yeah we don’t really have a lot of iron in the water on this area. We do have a lot of houses with copper pipes, older ones with galvanized pipes. Our soil is red clay with a lot of iron. My pool steps need regular treatment with vitamin C because runoff leaves red mud on them.

Charlotte water seems like a good source.

So, my profile says Charlotte but I'm actually in Fort Mill, SC just across the border (I figure folks had a better chance of getting a sense of where the pool is saying Charlotte).

My plan on the next attempt is to truck in the water from Charlotte using a local company called Aqua Duck Water. I need to verify they use the municipal water in Charlotte. Fortunately my pool does not get ground run off from the red clay dirt in the area.

 

[poologant]

You assumed that you initially got the iron in via Chlorox salt. Could the same have happened again after the refill with that different brand if salt that you used? Do you have some salt left that you could dissolve in distilled water and test for iron?

Good idea, I do have some of the salt. I'll test it. I'll need to break out the digital scale to mimic a reasonable salt ppm like the pool would have but that is doable.

I used Diamond Crystals Solar Naturals.

On the next round I'm thinking about changing to Morton's bulk salt with no additives as that is what PB used initially years ago.

 

[poologant]

Then if done correctly, the fill water has iron in it. Significant amounts.

So....

I just got the test results back from MyTapScore (SimpleLabs). The test was their specialty test specifically for iron (ferric and ferrous). Here's the results:

• Ferric Iron - Tested, not detected
• Ferrous Iron - Tested, not detected

So, now I am really concerned about where the iron came from after the drain and refill.

When I last drained, I did an AA treatment, drained the pool. Refilled and rebalanced. Stains came back within a day or two.

 

[Orion7319]

Charlotte water seems like a good source.

So, my profile says Charlotte but I'm actually in Fort Mill, SC just across the border (I figure folks had a better chance of getting a sense of where the pool is saying Charlotte).

My plan on the next attempt is to truck in the water from Charlotte using a local company called Aqua Duck Water. I need to verify they use the municipal water in Charlotte. Fortunately my pool does not get ground run off from the red clay dirt in the area.

So your getting water from the Rock Hill plant same as me. From your other post, as you see we have no iron in our water. (Also our TA is 50 out of the tap BTW). Fort Mill is 90% newer construction homes so most likely you have PEX pluming. I have no idea where that iron could be coming from! I don’t see that you have a heater. You mentioned rust staining on your pool deck? That’s the only thing out of the ordinary. The salt you added is for water softeners and says it’s basically 99.6% pure so I wouldn’t think that would be it. I use the pool salt from Home Depot myself and never had a problem with it.

 

[poologant]

Fort Mill is 90% newer construction homes so most likely you have PEX pluming.

Mine is an older home, no PEX, copper and PVC instead. Plus, as you saw, the fill water from my spigot I use came back negative.

I don’t see that you have a heater.

I do have a heater, it is a Hayward with a nickel-copper exchange. It is only five years old. It seems unlikely that it is the source but I'm running out of places to look.

You mentioned rust staining on your pool deck? That’s the only thing out of the ordinary.

I have two very small holes (maybe an 1/8") that are pitting pretty deep (maybe 1"). They are reddish around the hole so I'm thinking it is rebar rusting. Nothing seems to be going into the pool though as I would expect a red trail leading into the pool. I don't have that.

This is maddening for me as I don't really want to AA treat then drain again only to have the iron stains come right back again. Previous 4 years had zero stains.

 

[duraleigh]

Can you post complete test results? Especially pH and TA but the rest, too, if you have them.

 

[poologant]

Can you post complete test results? Especially pH and TA but the rest, too, if you have them.

Can do, have it shortly.

 

[mgtfp]

Since ideas are starting to run out, here another one that's probably unlikely, but I'll mention it anyway.

A while ago, there was a batch of calcium increaser in Australia that created a brown deposit when dissolving in a bucket. I first couldn't reproduce that behaviour with the bag I still had at home, but with a new bag it happened to me as well. Another batch after that was OK again.

It never got resolved what the cause was, and unfortunately I didn't test a sample for iron. But I'm still wondering if that batch had an iron contamination.

If you have some left of your calcium increaser, then it might be worth testing a sample for iron to rule that out.

HY-CLOR Calcium Chloride impurities

I bought HY-CLOR brand Calcium Increaser from bunnings, put 2.5K in a bocket of water, left it 5 days, found that all the white pellets desolved wth dark brown sedements at the bottom of the bocket. Last time I put some in the skimmer basket in a cloth, I found the same color on part of the...

www.troublefreepool.com

And just a warning should you decide experimenting with calcium increaser: Dissolving that stuff is an exothermic reaction and putting large amounts into a water volume that's too small will create a lot of heat. For that reason I never dissolve more than about 1kg in a 10l bucket of water.

TFP doesn't recommend predissolving it for that reason, but after that experience I prefer to know what I'm putting in my pool. Confirming with a little bit that there is no deposit, and then dumping the rest straight into the pool, is the way to go for me. I only have to increase CH every couple of years anyway. I have quite soft water, resulting only in a small upward drift over summer, which gets sometimes more, sometimes less overcompensated by winter rain.

 

[poologant]

Can you post complete test results? Especially pH and TA but the rest, too, if you have them.

Got these from my last full test done a few days ago:

FC: 2.2 (FAS-DPD)
CC: 0.1 (barely changed color)
TC: 2.3
CYA: 30 (I am aware this is low, but I am keeping FC/CYA ratio in check (FC within 5% to 7.5% of CYA)
PH: 7.4
TA: 65
CH: 325
SALT: 2900 (TCell Meter), 3400 (Taylor Drop Test)
Pool Temp: 86

 

[poologant]

A while ago, there was a batch of calcium increaser in Australia that created a brown deposit when dissolving in a bucket. I first couldn't reproduce that behaviour with the bag I still had at home, but with a new bag it happened to me as well. Another batch after that was OK again.

I actually had the same thing happen (brown muck), and it is possible that may have been my original source of iron and not the Clorox Salt but seems others had the issue with the Clorox so that seemed more plausible to me.

When I did the drain/refill, I changed brands to PuriTech. It did not create the brown muck. I have some left over, I'll do the same distilled water mix to test it when I test the new salt.

TFP doesn't recommend predissolving it for that reason, but after that experience I prefer to know what I'm putting in my pool. Confirming with a little bit that there is no deposit, and then dumping the rest straight into the pool, is the way to go for me. I only have to increase CH every couple of years anyway. I have quite soft water, resulting only in a small upward drift over summer, which gets sometimes more, sometimes less overcompensated by winter rain.

I do the same thing for the same reason but I pre-disolve it all using a large trash can with lots of cold water from spigot. It gets warm but not to hot to handle and cools off quickly.

 

[duraleigh]

Those are pretty good numbers. Off the subject but I would suggest your FC around 4 with 30 CYA.

Anyway, the point of my post was I believe you will need to do the aa treatment one more time. I can't think of a way around it.

However, when you are finished, please adjust pH to 7.0 and TA down to about 60. That's a tad low for both but I think it will help keep your iron in solution so it won't precipitate to a stain. Might work well and it's pretty painless to do.

As for the source of you iron, I still think it's the pool water. I tested NO iron in my water but on the 6th year, it had finally gotten high enough it preciptated onto my vinyl liner

 

[poologant]

Those are pretty good numbers. Off the subject but I would suggest your FC around 4 with 30 CYA.

Anyway, the point of my post was I believe you will need to do the aa treatment one more time. I can't think of a way around it.

However, when you are finished, please adjust pH to 7.0 and TA down to about 60. That's a tad low for both but I think it will help keep your iron in solution so it won't precipitate to a stain. Might work well and it's pretty painless to do.

As for the source of you iron, I still think it's the pool water. I tested NO iron in my water but on the 6th year, it had finally gotten high enough it preciptated onto my vinyl liner

Yes, if I drain again I will definitely do another AA treatment and I'll drain without adding any chemicals. Without chlorine, I can't imagine it would stain. I also plan to flush out the lines at that time.