Color in pool water is a symptom, not a diagnosis

In this conversation, Rudy Stankowitz delves into the complexities of pool chemistry, particularly focusing on the role of copper and hydrogen peroxide in water treatment. He revisits a previous episode on ORP (Oxidation-Reduction Potential) and discusses the implications of misdiagnosing pool issues based on color alone. Stankowitz emphasizes the importance of understanding the underlying chemical conditions rather than relying solely on visual symptoms. He provides insights into how copper behaves in pool water, the effects of pH changes, and the common mistakes made in diagnosing and treating copper stains. The conversation culminates in a call for better questions and a deeper understanding of pool chemistry to improve industry practices.


Takeaways

The industry improves by revisiting ideas with better questions.
Copper chemistry is complex and often misunderstood.
Color in pool water is a symptom, not a diagnosis.
Hydrogen peroxide behaves differently than chlorine in pools.
Misdiagnosing copper as algae can lead to incorrect treatments.
pH changes can significantly affect copper behavior in water.
Copper can exist in multiple forms, each with different implications.
Understanding chemical conditions is crucial for effective pool maintenance.
ORP readings can be misleading without context.
Good operators pressure test their explanations rather than protect them.


Sound bites

"A green algae pool is cloudy and opaque."
"Copper can be blue, it can be green."
"Copper doesn't show up. Copper waits."


Chapters

00:00 Introduction and Acknowledgments
00:19 Revisiting the ORP Episode
01:25 Understanding Copper Chemistry
04:38 The Role of Hydrogen Peroxide
08:50 Misunderstanding Copper in Pools
14:43 Diagnosing Copper Stains
19:35 The Effects of pH on Copper
26:13 Complexities of Copper Staining
29:50 Conclusion and Key Takeaways

Transcript

SPEAKER_03 0:53

As reported in San Angelo Live, a San Angelo pool construction case that drew local attention over the past year has now reached a legal resolution. According to reporting, the case involved a local pool contractor who was charged in connection with an unfinished residential pool project. Court records cited by the outlet indicate that homeowners paid a significant portion of a contracted amount for a pool and backyard project that was never completed. San Angelo Live reported that the matter was scheduled to proceed to trial, but was resolved through a plea agreement shortly beforehand. Under the terms outlined in the report, the defendant received deferred adjudication probation and was ordered to pay restitution. The publication noted that deferred adjudication means the case may ultimately be dismissed if all court ordered conditions are satisfied. As reported, the court's resolution did not include a conviction, and the outcome reflects a negotiated agreement within the Texas legal system. Anyone seeking further details is encouraged to review the original reporting by San Angelo Live or consult official court records in Tom Green County for the most accurate and up-to-date information.

SPEAKER_04 2:09

Hey, pool dudes and dudats, it is Friday. So before we move on, I just wanted to really quick say to those of you that reached out with condolences last week, thank you. Deborah Swearington, I appreciate you so much as well. Everybody, I want to do something that actually matters. I want to clean something up. I want to add context and I want to acknowledge an excellent question that came in after not last week's, but the week prior, the ORP episode I did, because this is how the industry actually gets better. Not by pretending we said everything perfectly the first time, not by digging in our heels, but by revisiting ideas when better questions show up. So after that ORP episode aired, I received an email from Terry Arco at Hasa. And if you don't know Terry, you should. Terry comes from the chemical manufacturing side of this industry, the part where chemistry is not theoretical, it's consequential. Where decisions don't just cost money, they cost credibility, safety, and sometimes careers. When Terry offers a theory, it's considered and it's worth listening to. So Terry was referring to the part of the episode where I talked about the 2016 Olympic diving pool in Brazil turning green, probably the most watched swimming pool on the planet at the time. And he shared an alternative explanation that circulated quietly for years. An explanation that does not center on algae, an explanation rooted in copper chemistry, specifically copper sulfate use, high sulfate source water, and the addition of hydrogen peroxide, low pH peroxide, causing copper to come out of solution and show color. And Terry's central point, which is fair, is visual. Yeah, the pool was green, but it appeared clear. You could see the bottom, and that matters.

SPEAKER_02 4:42

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SPEAKER_01 5:48

This week's breaking news doesn't come with flashing lights or dramatic headlines, but it has real consequences for how pool service professionals do business right now. Global copper and silver prices have surged to near record highs. Those metals are embedded in the equipment this industry relies on every day. Motors, circuit boards, variable speed pumps, automation systems, heaters, and controls. When those markets spike, the impact does not stay in financial news. It shows up in supplier pricing, replacement parts, lead times, and tightening margins at the service level. Manufacturers and distributors are already signaling pricing pressure. Quotes written weeks ago may no longer hold. Service companies that do not build buffers into equipment installs or clearly define expiration dates on proposals risk absorbing those increases themselves. This is not speculation. It is the same slow squeeze the industry has seen before, driven this time by raw materials instead of logistics. At the same time, safety and liability expectations continue to tighten. Active pool recalls remain in effect, and service professionals working around affected systems need to understand exactly what they are touching. Documentation, communication, and scope clarity are no longer optional. Ignorance does not protect you after the fact. Layered on top of that is a quiet regulatory shift around energy efficiency, safety standards, and compliance expectations. Even in states where laws are not fully enforced yet, the expectation curve has already moved. Customers will assume you advise them. Inspectors will assume you documented it. Attorneys will assume you knew. This is not panic news, this is pressure news, a kind that reshapes pricing models, liability exposure, and operational decisions if you are not paying attention. And that brings us to where these conversations are happening in real time. On Saturday, February 14th, at the Western Pool and Spa Show, Rudy Stankowitz will be on stage multiple times addressing these exact pressures from different angles, because none of them exist in isolation. The day begins with legislation and litigation. Are pool service and contractors the next target? A grounded look at where regulation, enforcement, and liability trends are heading, and what service professionals need to understand before they become case studies. Later, the mentor model. Creating the next generation of pool pros focuses on why labor shortages, burnout, and skill gaps persist, and how mentorship, done correctly, is not a feel-good concept but a strategic business decision. The day concludes with mental health, burnout, and boundaries in the pool industry, an honest discussion about the psychological load of service work, and why ignoring burnout is not toughness. It is risk. Beyond the show floor, these same issues are also front and center at the The Chlorine Institute 2026 at their annual meeting on March 23rd through 26th in Houston, Utstitute, Texas. At that meeting, Rudy will be taking an in-depth look at two topics that continue to be misunderstood and mismanaged across the industry. Black algae and cyanuric acid reduction. This includes reframing black algae as cyanobacteria, why traditional treatments often fail, and how misidentification leads to surface damage and repeated outbreaks. It also includes a detailed examination of cyanuric acid reduction methods that challenge the long-held belief that draining water is the only solution. These are not academic discussions. What happens in rooms like this shapes safety guidance, best practices, and regulatory expectations long before they ever reach the service truck or the backyard gate. The takeaway this week is simple. The water may look calm, but the business environment is shifting. Pricing needs adjustment. Documentation needs consistency. Mentorship needs structure. And mental health needs to be treated as an operational issue, not a personal weakness. Saturday, February 14th, at the Western Pool and Spa Show, and the ongoing discussions on March 23rd through 26th in Houston at the Chlorine Institute's 2026 annual meeting are reminders that the pool industry is changing whether we acknowledge it or not.

SPEAKER_08 11:01

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SPEAKER_04 11:40

So Terry was referring to the part of the episode where I talked about the 2016 Olympic diving pool in Brazil turning green, probably the most watched swimming pool on the planet at the time. And he shared an alternative explanation that circulated quietly for years. An explanation that does not center on algae, an explanation rooted in copper chemistry, specifically copper sulfate use, high sulfate source water, and the addition of hydrogen peroxide, low pH peroxide, causing copper to come out of solution and show color. But take into consideration that hydrogen peroxide is a weak acid, not a strong acid. It has a pH, just a hair above six. Add to that the property in muriatic acid, chemically HCl, that would cause copper to present green is not the acidity of the liquid. But the chloride content, it is also not documented, or even likely, a dose of acid with the necessary chloride would have been added, as well as the peroxide, as the peroxide, as we just discussed, is indeed an acid, albeit a weak acid. So the chemistry needed for the reaction, copper present or not, is just not there, especially after the peroxide neutralized the existing level of chlorine. And Terry's central point, which is fair, is visual. Yeah, the pool was green, but it appeared clear. You could see the bottom, and that matters. So a green pool, a green algae pool is cloudy and opaque, a green copper pool is transparent. That distinction is fundamental, and it's chemistry, not opinion. So now, before we go any further, I want to add an important piece that sits right between Terry's theory and my continued stance. I've also seen photographs of the pool. I've reviewed them carefully. In my professional opinion, what's visible in those images does not fully match the classic Gatorade green clarity, typically indicative of a copper-dominant chemistry event. When copper is the primary driver, especially in cases like hexaaqua copper or tetrochlorocuprate, the water tends to be dual-like transparent. Light passes cleanly through it, the color is vivid, but the water column remains optically sharp. That's not exactly what those photos show. What we see instead is green water that lacks that crisp optical clarity that you'd expect from copper expression alone. There's a softness to the light, a diffusion, something that suggests biological contribution, not just dissolved metal chemistry. That observation is a primary reason I still favor the International Olympic Committee's findings. Not because copper chemistry isn't plausible, it absolutely is, and not because Terry's explanation lacks merit. It does not. But when you combine the visual evidence with the operational context, the photographs lean away from a clean copper-only event and toward a sanitation failure that allowed biological growth to occur. And the chemistry to back it is just not there. That doesn't negate copper's role, it contextualizes it. Which brings us to what we said then. At the time of the Olympics, the IOC and competition operators attributed the incident to algae. That explanation was widely reported, including by CBS News, and it aligned with what Bob Lowery shared with me at the time. And I want to be very clear here. I still favor the Olympic Committee's findings, not because copper chemistry is impossible, it isn't, but because the official investigation had access to the data that none of us outside that control room are ever going to see. They had water logs, they had feed records, they had controller histories, they had real-time operational detail. We did not. So this is not about declaring a new winner. This is about understanding layers. What Terry's email highlights and why I'm glad he sent it is that more than one chemically valid failure mode likely existed at the same time. And that doesn't weaken the ORP conversation. It actually strengthens it because whether the green came from algae growth or from copper expression or both, the root issue was the same. Oxidation chemistry was misunderstood in real time. And this is where we need to slow down and talk about peroxide for a moment because peroxide is the quiet troublemaker in this entire story. Hydrogen peroxide does not behave like chlorine. It does not disinfect the same way. It does not oxidize the same way. It absolutely does not report itself honestly to ORP systems. Peroxide can elevate ORP readings while actively suppressing free chlorine. To be truthful with you, can mask sanitizer loss and create the illusion of oxidative capacity while removing the very disinfectant we rely on here for biological control. So when peroxide enters a system, especially an automated one, you can get that perfect storm. Chlorine is neutralized, ORP remains elevated, the controller stops feeding oxidizer, biological demand increases, metals destabilize. That's not hypothetical. That is a documented failure mode. So when we say ORP lied, what we really mean is ORP was asked the wrong question. ORP never promises to identify which oxidizer is present. It never promises to explain why oxidation occurs. It only reports that electron transfer is possible. That's it. So what we said then was based on the best publicly available information at the time. What we know now is that the chemistry was more complex. That's not backpedaling, that's refinement. And that refinement is exactly why ORP cannot be treated as a truth machine, because ORP does not know why oxidation is happening. It only knows that something is happening. And if you don't understand what's contributing to that signal chlorine, peroxide, metal, stabilizer, sunlight, you can make the right move for all the wrong reasons and still end up on international television with a swamp vomit green pool. That's the lesson. And it doesn't stop at the Olympics because the Olympics pool wasn't unique. It was just visible. This same chemistry plays out quietly every single season in backyards, hotels, apartment complexes, and commercial facilities all over the world, just without cameras, without headlines, and without public post mortems. Which brings us to copper itself.

SPEAKER_06 19:17

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SPEAKER_02 19:47

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SPEAKER_07 19:49

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SPEAKER_00 20:46

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SPEAKER_04 21:16

Copper is one of the most misunderstood elements in swimming pool water because it doesn't behave like a contaminant. It behaves like a participant. It responds to conditions. Copper can be blue, it can be green, it could be violet skies, it could be teal, it could be purple, it could be gray if you like, it can be black. Okay, I'm gonna stop now. But you get the point. And the same copper can move between those expressions depending on pH, alkalinity, oxidizer strength, chloride concentration, cyanuric acid, and redox conditions, which is why stain diagnosis is often so strong and why treatment frequently makes those things worse. Copper doesn't suddenly appear, it waits. When copper sulfate dissolves, it forms hexaaqua copper, which is six water molecules coordinated around a copper ion, producing a brilliant, crystal clear blue. The pool looks stunning, clean, inviting, has that crisp, clear Caribbean look, and that's the trap because that copper is now fully dissolved, mobile, and waiting for chemistry to shift. Rising total alkalinity or pH increases the carbonate ion concentration. Copper carbonate hydroxide forms insoluble, cloudy, often settling or slowly filtering out. Drop pH too aggressively after that, and the color shifts again. Add acid in the presence of copper and chloride ions, which displace water molecules, forming the tetrochlorocuprate. The pool turns green, sometimes shock green while remaining. Clear. That's the Gatorade green we were talking about, but not all green water is that. Raise pH with soda ash or allow pH to creep in a salt water pool and copper hydroxide precipitates, teal stains, smurf blue walls, then panic, broadcast calcium hypochlorite into copper-bearing water, and copper oxidizes into cupric oxide. It's actually a degradation reaction. You get the charcoal blotchy black mottled stains all over the walls and floor of the pool. Terrifying at first, sometimes reversible, not always. You're in rare copper territory. Add a high stabilizer. This is where it really gets bucknutty. Purple haze, reddish violet blotches, tiny crystalline structures that behave nothing like algae and nothing like scale. And here's the key point: none of that requires more copper. The copper was already there. The chemistry moved. This is why copper problems are not sanitation failures. They are chemistry balance failures. And this is where ORP re-enters the conversation. ORP will not warn you that copper is about to express. ORP will not distinguish chlorine oxidation from peroxide oxidation. ORP will not alert you to metal destabilization. ORP will report that oxidation is occurring. And if you treat that signal as a command instead of a report, you can drive the system directly into a metal disaster while thinking you're doing everything right, which brings us full circle. The Olympic pool didn't fail because someone didn't care. It didn't fail because ORP is useless. It failed because oxidation chemistry is layered and one layer was misunderstood in real time. That's the same misunderstanding shows up every day when copper is misdiagnosed as algae, when staining is chased with shock, when acid is dumped without context, and when ORP is trusted without interrogation. So yeah, Terry's copper theory is chemically valid. Yes, the Olympic Committee's algae finding still stands. And yes, both can exist within the same event. That's not a contradiction. That's chemistry, and chemistry does not care which explanation makes us more comfortable. It only responds to conditions. That's why this industry doesn't improve by clinging to old explanations. It gets better by revisiting them with better questions. And that's what we just did. All right, now here's why I'm not going to move on too quickly. Because the Olympics story is a headline, sure, it's a viral moment, it's a meme, it's the kind of thing that becomes pool guy folklore, but operationally it's not really all that special. It's simply the most televised example of something that happens every single day in the field. A pool turns a specific color, and everyone rushes to diagnose it by the color alone. And I'm telling you right now, as professionally as I can, color is not a diagnosis. Color is a symptom. Green water can be algae, green water can be copper, green water can be a blend. Suspended solids, organics, filtration issues, and a sanitizer gap can cause green water. Green water can be a chemical expression, poor optical clarity, sunlight, and demand. So the real question isn't what color is it? The real question is what chemical conditions created that color and what did we do to cause that condition? This is the perfect transition into the second half of this episode because if the Olympic pool taught us anything, it taught us this. You can be doing something and still be doing the wrong thing because oxidation is not the same as sanitation. And that's why we're going to talk about copper stains in a way that can actually help you diagnose what you're seeing without guessing. Okay, my friends, let's talk about one of the most frustrating things we can deal with in water: stains, discoloration. That moment when the customer sends you a picture like you personally poured Mountain Dew into their pool. Here's why metal issues are such a pain in the ass. Metals can be present as a bunch of different colors depending on chemical conditions. Blue, green, teal, purple, gray, black. We went through it before. This time I didn't sing it, but hey. And that's the part that makes diagnosis tricky because the color you see isn't always the metal itself. It's the metal reacting to whatever you did to the water last. So today we're going to focus on copper, not because copper is the only metal that stains pools, but because copper is standard. Copper is sneaky, and copper is the culprit way more often than people want to admit. It gets introduced constantly. Copper-based algecides, mineral systems, certain source waters, heater corrosion, low quality salt, and sometimes a well-meaning homeowner who read one internet post and decided copper sulfate was their spiritual calling. So let's hit the feed store and dump a bunch in a skimmer. Copper has been around forever, literally one of the oldest metal objects ever found, and all was found made of copper, and it dates back over to 7,000 years old. So yeah, copper's ancient. And yeah, copper is still ruining pool finishes in 2026. So here's the big idea I want you to lock in on. Copper doesn't show up. Copper waits, it sits in the water, dissolved, behaving. And then the water chemistry changes and copper decides it's going to get all dramatic. And copper has multiple moods. Each mood has a name, and each mood has a look. Let's walk through them. When you add a copper algebra like copper sulfate pentahydrate, and it dissolves, you can get a brilliant copper sulfate blue, and the pool can still be crystal clear. This is the copper form that tricks people because it looks clean, it looks sharp, it looks like a Pinterest pool. That clear blue color is basically copper dissolved in water with water molecules surrounding it. Chemists call it hexaaquacopper. But here's the warning that blue clarity does not mean safe. It means copper is now fully available to stain your customer's pool the second the chemistry shifts. In pool chemistry, we specifically use chelated copper in minerals like Blu-ray XL and algecides. We are using the word chelated in a very specific and functional way, not in the loose marketing sense that gets thrown around. Chilated means the copper ion has been intentionally bound to a chelating agent, a ligand that wraps around the metal and holds it in a stable, soluble coordination state. The goal of that chelation is not to remove the copper from the water, but to control how it behaves once it's there. In practical pool water terms, chelated copper is copper that has been chemically treated so it remains in the form it is already in and does not readily complex, precipitate, or react further with carbonates, hydroxides, phosphates, or pool surfaces. The collating agent occupies the copper's available coordination sites, which prevents the copper from forming new complexes that would otherwise lead to staining, plating, or the formation of insoluble copper compounds. The copper stays dissolved, evenly distributed, and predictable instead of acting like free copper that goes looking for something to attach itself to. This is where the distinction really matters for operators. Free or poorly stabilized copper will happily react as soon as conditions shift. As pH rises, it can bind with hydroxide or carbonate. When balance drifts, it can precipitate or plate out. It can end up on vinyl, hair, uh fittings, or tile because nothing is restraining it. Collation exists specifically to prevent that behavior by locking the copper into a controlled coordination complex. It's also important to understand what collation does not mean. Collation does not turn copper off, it does not eliminate its biocidal properties. Instead, it regulates them. The copper can still exert antimicrobial effects through controlled ion exchange at the boundary of the shellate, but it is far less likely to behave aggressively or unpredictably when water chemistry changes. When copper is happily dissolved and complexed with water molecules, you're looking at a system where copper is present but is stable enough to stay in solution. That stability isn't magic. If you end up with the black or charcoal or the oh shit stains, now there's one that'll make a pool tech's eyes roll in the back of their head, make their soul leave their body and their head spin in circles. If you have copper in the water and you broadcast calhypo across the surface, you can trigger blotchy gray charcoal or black staining on the pool walls and floor. And yeah, the customer is going to shit. This is cupric oxide. This happens because the potent oxidizing agents converts copper into an insoluble black form in a degradation reaction that stains aggressively. It can be temporary, but you know what? It can also be severe. And here's the key if you catch it early, I've already shown you. I have videos showing this. We found that aluminum sulfate will remove fresh copper staining. Just sprinkle a little bit over the area, just enough to cover it. Gone in 60 seconds. I hear you. You know what? It goes away on its own after 12 hours. Sometimes, not always, either way, I'm going with the alum because whether I explain to my customer they have black blotchy stainings that are going to go away on their own or not, when they get home and go in their backyard and look at their pool, they're going to have a frigging cow. So I would rather just take care of it right then and there and have the stain not be there. So if we end up with coopered oxide staining, I'm just going to sprinkle a little bit of aluminum sulfate over the spot. Don't have it on hand. Go to the spice aisle in your grocery store, get them a Cormix, a couple of those things. That should be enough to cover the stained area. Let's just connect this back to oxidation chemistry misunderstood, because the most common scenario I see looks like this. Someone thinks they're solving algae. They shock hard, they broadcast calhypo, they oxidize copper, they stain the floor black, then they claim the chlorine did that as if it acted alone. No! Copper was present. It had to be. The chemistry moved. The oxidation environment changed in copper expressed. Chlorine did not ruin the pool. The chemistry did what chemistry does. I know a lot of people hear metal stain and they immediately reach for ascorbic acid, vitamin C. And yeah, that works great if you're dealing with an iron stain. Ascorbic acid does not work well on copper stains. In fact, it'll turn them black. So before you commit to a complete treatment, do what pros do test a small spot with a Jack's Magic stain ID kit. And for God's sake, make sure you own a copper test kit. Lamotte offers several copper test kits. The Lamotte 36119 Low Range Copper Testing Kit is a simple color chart kit for measuring copper from 0.05 to 1.0 ppm. Owning one of these kits is a must-have for anyone who calls themselves a pool professional and doesn't want to wild west it poolside. Don't waste time and money dumping a complete treatment into the pool and hoping for a miracle. It's not going to work. If we're looking at copper staining, aluminum sulfate is a better way to go. Ascorbic acid works well at removing iron stains because it is a natural electron donor, so it can bleach stains by donating electrons that the chlorine stripped away. Or said differently, ascorbic acid giveth and chlorine taketh away. So the reason copper causes so much confusion in the field is that it doesn't have a single look. Copper is not one problem. Copper is a shape shifter. And if you misdiagnose copper as algae, you will treat it wrong. If you shock it harder, you might oxidize it to a darker color. And if you slam acid, you might just turn the whole damn pool green. If you raise the pH, you might stain it teal. If you ignore the stabilizer, you might grow purple crystals that seem to pay rent. Copper does not care about your intentions, it only cares about conditions. So the professional move, the expert move, is to stop reacting to color and start interrogating chemistry. Because if copper is in that water, the question isn't why is the pool green? The question is, what did we change that gave copper permission to show itself? That's the job, all right. That's copper stains and swimming pools. You know, instead of farting around with a vitamin C tablet or just sprinkling alum on stuff willy-nilly, why not get one of the Jack's Magic stain ID kits? That'll tell you what's going on and give you direction right off the bat. It's the quicker, safer, more professional way to go. Now, let me stitch two halves of this whole thing together so nobody walks away thinking that this was two separate topics that had nothing to do with one another. This was indeed one topic. The Olympic pool story was not a fun Olympics anecdote. It was the most televised example of a universal field truth. Oxidation is not synonymous with sanitation. And green is not a diagnosis, it's a symptom. That pool went green under the brightest spotlight in the world. And the reason it matters is that the same mechanical thinking error happens in your market every week. Somebody treats smell with peroxide and forgets what peroxide does to chlorine. Somebody chases an ORP set point without understanding what ORP is actually reading. Somebody sees green and assumes it's algae. Somebody adds acid fast and turns copper green. Somebody shocks hard and oxidizes copper to black. Somebody raises the pH and plates copper onto the walls. Somebody ignores CYA and gets weird metal cyanurate behavior. And then everyone argues about what caused it. While the real cause is they weren't interrogating the system. So yeah, I'm grateful Terry Arco emailed me. He's a good friend. Grab a cup of coffee at the Western show, maybe breakfast. It was definitely a legitimate chemical critique. It was professionally grounded and it was a reminder that good operators don't protect explanations, they pressure test them. And yeah, I still favor the Olympic Committee's algae finding because they had operational data that the public didn't, but the more resounding win is that Terry's Terry's input forces a more mature takeaway. Multiple chemical valid failure modes can coexist. Peroxide can mask chlorine collapse. The wrong oxidizer can elevate ORP, and copper can express under the exact kinds of interventions people use when they're trying to fix a crisis fast. So the real lesson, the same one I've been pushing all along. Don't worship numbers, interrogate systems. Don't diagnose by color, diagnose by conditions, because the water is always telling the truth. You just have to ask the right questions. That's all I got for you this week. I'm Rudy Stankowitz. This is the Talking Pools podcast. Until next time, be good, be safe.