Iron stain keeps returning

[Nanos203]

Hi guys,

My pool has persistent iron staining. Two seasons ago I drained and acid washed. Last season I did an AA treatment and then drained. Pool was clean all summer and closed clean. I just opened the pool and found iron stains (confirmed by absorbing acid test) again. The iron stains are concentrated in the shallow end and specifically on the area that was below water for the majority of the winter e.g. areas that were above the initial water line when I closed the pool did not suffer staining despite being above the water line by the time I opened. The spa does not have any staining. The water repeatedly tests negative for iron and copper at my local Leslie’s— literally 0.

The plaster is passed it’s useful life and is failing. I believe I have areas where rebar is rusting through. But I would expect tests to show meaningful iron levels in the water and they never do, even in the past.

Picture show the staining as well as results of small AA test on the steps which lifted the stains instantly.

Any ideas as to what’s going on?

Thanks!

 

[ajw22]

The iron stains are concentrated in the shallow end and specifically on the area that was below water for the majority of the winter e.g. areas that were above the initial water line when I closed the pool did not suffer staining despite being above the water line by the time I opened.

That is because without the pump running fresh runoff water stratifies and sits on top of the heavier pool water that has a lot of solids in it.

That points to the iron being in your pool water at close and not coming from something from fertilizer runoff during the winter.

The spa does not have any staining.

That is interesting.

The water repeatedly tests negative for iron and copper at my local Leslie’s— literally 0.

When did you test the water for iron?

Once iron deposits on surfaces it is not in suspension in the water and will not show on water tests.

Did you test the water for iron right before closing?

Any ideas as to what’s going on?

What chemicals do you put into the water at closing?

 

[Texas Splash]

One thing for sure, you can't place a lot of faith in the store testing. Their testing for metals is just as inconsistent as it is for normal levels. Current chemistry and the amount of iron precipitated out in the water all influence testing. The number one thing to figure out here is where is this iron coming from? Well water? If not, then your city water? Have you checked your county annual water reports? Any other pool owners nearby with the same problem? What about hardware in/around the pool? Old plumbing sources? Anything that may be disintegrating? What about the cover hardware? Since you drained two years ago, the new iron has to be coming from somewhere.

 

[Nanos203]

@ajw22 @Texas Splash

I closed the pool with some extra bleach and that's it. Pool cover is new, no corrosion. My sense is that whatever is happening it's originating in the main pool, not the spa, since the spa opened clean and the pool opened stained. The staining appears to be a lot worse in the shallow end than the deep end. The metal trim on the light fixture in the shallow end shows some corrosion on it while the deep-end one looks clean. Could it be from that? What would cause the fixture to corrode? The light itself works fine. When I drain the pool after AA treatment, I am going to inspect further. I will also do another metals test at pool store during AA treatment-- that theoretically should show iron in the water since it's being released from the plaster during the AA treatment.

Ack on pool store testing. Is there an at-home test I can do? I have city water and use that to fill the pool. Here is the water company's test report. I'm not sure how to interpret it.

 

[JoyfulNoise]

The iron is coming from your water supplier. You live on the east coast in an old part of Connecticut and all of the water delivery systems there are ancient. There are likely miles and miles of old cast iron piping in the system that only gets changed out to PVC when the pipes burst.

Pool store testing will likely not detect the iron because metal testing is very complex and the color changing tests are very limited in what types of metals can be detected. You would be much better off sending out water samples to an independent testing laboratory for analysis as they utilize more sophisticated techniques.

Your municipal water report doesn’t show any list for iron because iron is not a reportable contaminant in water supplies (there’s no health risk associated with iron). Since they are not required to report it, they will not test for it.

The corrosion on the light ring is likely just from age or, perhaps, the bonding wire is broken. When the pool is drained, you should remove the light and thoroughly inspect the light niche to ensure everything is properly connected. You should also find and check the junction box to make sure all electrical connections are sound.

 

[Nanos203]

@JoyfulNoise You're probably right.. but wouldn't that imply everyone around me would have iron staining issues in their pools? I haven't heard of anyone else dealing with the issue...

 

[JoyfulNoise]

@JoyfulNoise You're probably right.. but wouldn't that imply everyone around me would have iron staining issues in their pools? I haven't heard of anyone else dealing with the issue...

It depends. If a lot of people are using trichlor tabs and their pools are acidic from overuse, that could easily mask iron issues. Maybe some have iron filters on their water supply (my parents had that in their home on Long Island many decades ago). Perhaps your neighbors are using sequestering agents regularly, that would mask iron issues. Maybe you’re just really unlucky. Hard to say for sure.

Metal staining is always a very tricky issue to deal with. For some pools it can be a regular occurrence and a major hassle.

 

[Nanos203]

It depends. If a lot of people are using trichlor tabs and their pools are acidic from overuse, that could easily mask iron issues. Maybe some have iron filters on their water supply (my parents had that in their home on Long Island many decades ago). Perhaps your neighbors are using sequestering agents regularly, that would mask iron issues. Maybe you’re just really unlucky. Hard to say for sure.

Metal staining is always a very tricky issue to deal with. For some pools it can be a regular occurrence and a major hassle.

What do you make of the spa being clear of staining?

 

[JoyfulNoise]

What do you make of the spa being clear of staining?

Hard to say really. Perhaps it’s more filtered than the rest of the pool or was less subject to chemical variations over the winter …

Is it a raised spa?

 

[Nanos203]

Hard to say really. Perhaps it’s more filtered than the rest of the pool or was less subject to chemical variations over the winter …

Is it a raised spa?

It's a raised spa and shares same plumbing and filter...

 

[Nanos203]

So I did the AA treatment this morning. It’s truly magic. Turns out I didn’t appreciate the extent of the staining which was indeed through the main pool but not in the spa. I’ll report back my findings in the light niches when I drain. If it’s not that— could it be the heater?

 

[JoyfulNoise]

Your heater has a copper core. AA would not remove copper stains.

 

[JoyfulNoise]

One thing you can’t change but could be a contributing factor … red bricks. Your deck is entirely made of red bricks.

Guess what makes bricks red?

 

[Nanos203]

Some more info— now with the iron out of the walls and into the water, I got a test from pool store. 0 iron and 0 copper in the water. Guy working said he’s been getting non-zero readings all day, some even significant, so believes his equipment to be working.

I called local pool water company— they get their water from the same place I do— the water utility so would be dumb to buy from them. I really don’t think it’s the water supply.

@JoyfulNoise that could be it and adds up wrt spa— no bricks around spa just flagstone. Although water circulates from one to other but possible winter rains washed brick iron into the pool itself. But the I would expect to see staining above the closing water line rather than strictly below. I’m completely baffled.

Could it be organic stains? Prolonged SLAM didn’t remove them but the plaster is old and brittle/porous. Would AA remove organic stains or only iron?

 

[JoyfulNoise]

If there is AA or a sequestering agent in the water, iron testing can give false zero results because the iron is too tightly bound to the sequestrant. Typically bound-iron analysis requires an acid digestion step to destroy any organic that might be chelating the iron. This is why metal testing is tricky.

AA only removes iron stains, it down nothing for organic stains.

 

[Nanos203]

@JoyfulNoise Pool is draining. Down to shallow end so far so posting pic of light fixture. Can’t imagine this is the issue given the amount of staining. Thoughts?

 

[Nanos203]

Deep end light and niche clean.

Was hoping to find a smoking gun!

 

[JoyfulNoise]

That shallow end luminaire is showing signs of significant corrosion as is the retaining ring.

Is the bonding wire (green wire) still connected and showing conductivity to the rest of the bonding system?

I’m not saying the light is the cause of your stains but it’s certainly not in good shape and deserves some exploratory maintenance.

Are all the electrical connection back to the junction box good? No signs of damage, overheating, burnt wiring, etc..

 

[Nanos203]

The saga continues for anyone following. I drained and refilled pool, rebalanced chemicals, etc. Within 36 hours I’m noticing stains returning. Also noticing the color has a slight green hue. Before AA treatment and before draining, same hu. After AA, turned to blue hue. Drain and refill, back to green hue. I’m thinking it’s actually the stains on plaster changing the hue of the water. I feel like I’m going crazy.

@JoyfulNoise I removed and inspected the shallow light. Seems rusty. I signs of water intrusion. The lamp itself was ever so slightly damp, almost like dew. Wondering if it wasn’t 100% dry when I changed a bulb a few years back and trapped some moisture inside? Is what I have salvageable or should I replace it?

 

[W.J.Christy]

Perhaps putting some polyfill in the skimmer will help remove and potential iron in the water if its there. It may be worth putting an iron filter on the pool fill line as well just in case.