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The Pool Envy® Podcast goes beyond surface-level swimming pool advice to examine the standards, systems, evidence, and professional judgment behind pool construction, safety, operation, and failure.
Hosted by Jason Davies, a licensed swimming pool contractor and independent consultant, the show explores pool code compliance, construction defects, inspections, workmanship, water chemistry, equipment, litigation consulting, and expert-witness issues through real-world observations and practical explanations.
Created for pool professionals, homeowners, property owners, attorneys, and anyone who wants to understand not only what happens in a swimming pool—but why—each episode helps listeners ask better questions, recognize meaningful evidence, and distinguish confidence from informed judgment.
Pool Envy® — Standards, not suggestions.
From the job site to the code book, this is a Pool Envy Podcast where licensed pool professionals speak up. Code, compliance, craftsmanship. Hosted by Jason Davies. Licensed across Wisconsin, Florida, and Texas. Your deep end starts now.
Jason:I saw a news story recently with a headline that said summer heat was fueling algae growth in swimming pools. And, technically, sure, warm water can absolutely make conditions more favorable for biological growth. Hot water can increase chlorine demand. Strong sunlight can make maintaining chlorine more difficult. People are swimming more, and they're bringing more contaminants into the water.
Jason:All of that matters. But here's the problem I have with the headline. If hot weather caused pools to turn green, every swimming pool in the hot climate would turn green every summer. They don't. So instead of asking why does summer make pools green, I think there's a better question.
Jason:What changed that allowed algae to establish itself in the first place? Because algae doesn't need an invitation. It needs an opportunity, and that's what we're talking about today. Not just how to kill algae, not what bottle to dump into the water. We're talking about why it grows, what chlorine is actually doing, how cyanuric acid changes the conversation, why circulation matters, where organisms can hide, and why killing something doesn't necessarily mean you've removed it from the swimming pool.
Jason:And somewhere along the way, we're gonna visit a very strange warehouse full of waterbed mattresses and fluorescent lights. Stay with me on this one. It'll make sense a little later on. Let's start with something I think gets misunderstood. Your swimming pool is not sterile.
Jason:It's not an operating room. It isn't supposed to be sterile. The drinking water coming into your house has been treated. It's been disinfected and processed to make it safe to drink. That does not mean it's laboratory grade sterile water.
Jason:And once that water reaches your swimming pool, we immediately begin exposing it to the world. Air, dust, social media, rain, soil, leaves, grass, birds, insects, bathing suits, pool toys, cleaning equipment, and of course, people. Every person who gets into the pool brings something with them, skin cells, oil, sweat, microorganisms, whatever was on their feet, whatever was on their swimsuit, that's life. Microorganisms are everywhere. In fact, if we somehow eliminated microbial life from the planet, we'd have a considerably larger problem than a green swimming pool.
Jason:So the goal of chlorination isn't to create a completely sterile vessel where microorganisms can never enter. The goal is control. We want to maintain an environment where potentially harmful microorganisms cannot establish themselves at dangerous levels. And where algae, even if an algal cell or reproductive structure gets into the water, doesn't get the opportunity to turn one microscopic organism into billions of them. That's an important distinction.
Jason:Presence is not the same thing as growth. And that brings me to sourdough. Think about what somebody does when they're maintaining a sourdough starter. You're intentionally creating favorable conditions for microorganisms. You provide moisture.
Jason:You provide food. You maintain an appropriate temperature. You give them time. You're deliberately stacking the deck in their favor because you want that microbial population to become active and reproduce. And when conditions are right, it can happen quickly.
Jason:Now take that concept and turn it upside down. That's swimming pool management because your swimming pool already provides a lot of things biological organisms might enjoy. There's water. In the summer, there's warmth. There's sunlight.
Jason:There are nutrients introduced from the environment and from swimmers, and microorganisms are going to get opportunities to enter the vessel. So our job is to make one very important thing different. We maintain conditions where those organisms cannot establish a thriving population. Sourdough is an ecosystem we're intentionally encouraging. A swimming pool is an ecosystem we're intentionally discouraging.
Jason:And that's why I don't particularly love the question, where did my algae come from? It could have come from all kinds of places. The more useful question is, what changed that allowed it to grow? Because algae doesn't need you to add algae. It needs you to provide the opportunity.
Jason:And this is where we get into one of my favorite sentences in swimming pool chemistry. I have chlorine. Okay. How much? Three parts per million.
Jason:Okay. What's your cyanuric acid? I don't know. Now we're getting somewhere because simply knowing that free chlorine exists in the water doesn't tell me everything I want to know about how that chlorine is behaving. Cyanuric acid, what most people simply call stabilizer or conditioner, is enormously useful in outdoor swimming pools.
Jason:It helps protect chlorine from rapid destruction by ultraviolet light. Without it, sunlight can consume chlorine very quickly. But that protection comes with chemistry attached to it. As cyanuric acid concentration increases, the relationship between chlorine in the water and the amount immediately available in its most active sanitizing form changes, which is why three parts per million of free chlorine doesn't necessarily tell the same story at 20 parts per million of cyanuric acid as it does at 80 or a 100. That's where you hear people talk about the 7.5% concept.
Jason:The idea is that a minimum free chlorine concentration around 7.5% of the cyanuric acid concentration can be used as a practical operating relationship. So if CYA is 47.5 would be three parts per million free chlorine. If CYA is 80, you're looking at six. Now, I wanna be very clear about this. I'm not presenting 7.5 as some universal law carved into a stone tablet.
Jason:I'm not good with hieroglyphics. Different standards, codes, operating philosophies, and bodies of research approach chlorine and cyanuric acid differently. What I want you to understand is the principle. Cyanuric acid concentration matters when we're talking about chlorine effectiveness. I have chlorine is not the end of the conversation.
Jason:Chlorine is doing several things for us. First, it's a disinfectant. It helps inactivate susceptible microorganisms. Second, we maintain a residual. That's important.
Jason:We don't want to add chlorine, have it immediately consumed, and then wait around completely unprotected until somebody adds more. We maintain sanitizer in the water so that there's an ongoing defense against the next contaminant that enters the vessel. Third, chlorine is an oxidizer. It's reacting with oxidizable contaminants introduced into the swimming pool because there's something worth remembering. Oxidation is not the same thing as removal, and that distinction is going to become important in a minute.
Jason:People tend to imagine chlorine as some magical eraser. Put chlorine in, bad stuff disappears. That's not quite how a swimming pool works. Sometimes chlorine destroys or transforms a contaminant. Sometimes it changes what form something is in.
Jason:Sometimes material becomes particulate and gets captured. Sometimes it remains in the system in another form, and that's where we're going to take our little field trip. I want you all to imagine an old warehouse from the late nineteen seventies. Not a nice warehouse. One of those weird liminal space warehouses that looks like nobody has been inside since 1978.
Jason:The carpet is a color that doesn't exist anymore. The walls are beige. The ceiling goes on forever, and there are long fluorescent tubes buzzing overhead. Somewhere in the distance, something is humming, and you don't particularly know what it is. Now, fill this warehouse with waterbed mattresses, hundreds of them, big old waterbed mattresses, and every one of those mattresses contain something different.
Jason:That's our swimming pool, not literally. Please don't call me and tell me that your water has mattresses in it. We're building a mental model here. Some material in pool water is freely available. Some material is chemically tied up.
Jason:Some is incorporated into biological organisms. Some is trapped in debris. Some is captured in the filter. Some may be sequestered. Different things exist in different forms.
Jason:And here's a phrase I want you to remember. Contained is not the same thing as removed. Let's say one of those waterbed mattresses represents algae biomass. Algae needs nutrients to grow. Among those nutrients is phosphorus.
Jason:When algae grows, some phosphorus can become incorporated into that biological material. So imagine some of the phosphorus inventory in our warehouse is now sitting inside one of these giant waterbed mattresses. Then we kill the algae. Great. But what happens next?
Jason:The dead algae doesn't teleport out of the pool. That biological material is still there. It can be oxidized. It can decompose. It can break apart.
Jason:Some of it can be filtered. Some of it can settle, and nutrients contained in that biomass can eventually be recycled back into the surrounding water. So that giant waterbed mattress starts deteriorating. It springs a leak. What's inside begins mixing with everything else in the warehouse.
Jason:We didn't create new phosphorus. It was already there. It changed form. That's important. Killing algae doesn't manufacture phosphate, but phosphorus that has been incorporated into biological material can eventually become available again as that material breaks down, which gives us another very simple rule.
Jason:Dead isn't gone. If you kill a bunch of algae and leave all that dead biomass in the swimming pool and filtration system, you haven't necessarily removed everything that algae was made of. You changed its condition. Removal is another job. Now look up.
Jason:We've got those old fluorescent tubes hanging from the ceiling. Let's use those for another idea, sequestration. There are products used in swimming pools to manage metals such as iron and copper. Many of them use phosphonate chemistry. The purpose is essentially to keep metals under control so they're less likely to precipitate or create staining problems.
Jason:But here's the important part. Sequestered doesn't mean removed. The metal hasn't necessarily left the warehouse. We've changed how it's behaving. So imagine that fluorescent tube represents the sequestration chemistry keeping something contained.
Jason:It's relatively fragile. It has a useful life. Over time, oxidation and degradation can break down certain phosphonate based treatments and eventually crash. The fluorescent tube hits the floor. Now the thing we're managing can become available again.
Jason:And as phosphonate chemistry degrades, some of the phosphorus can eventually contribute to measurable orthophosphate. So somebody tests the pool six months later and says, where did all these phosphates come from? I don't even have fertilizer near my pool. Well, sometimes what you're measuring today started life as something you intentionally added yesterday to solve a completely different problem. Nothing magical happened.
Jason:Something already inside the warehouse changed form. Again, contained isn't removed. Now, because apparently this warehouse wasn't strange enough, somewhere next to one of those old water beds is one of those ancient quarter operated vibrating machines. Somebody puts a quarter into it, the whole place starts shaking. Everything that's leaking onto the floor starts moving around.
Jason:That's circulation. Circulation didn't create the material. It distributed it. And circulation works both ways in our swimming pool. We need good circulation because we want properly treated water reaching the entire vessel.
Jason:Steps, benches, corners, sunshelves, deep areas, behind ladders, everywhere. Your chlorine reading at the spot where you dip the test sample is not a force field surrounding the entire swimming pool. You sampled one tiny portion of a vessel containing thousands of gallons. That's why I make the distinction between turnover and circulation. Turnover is a calculation.
Jason:Circulation is what the water actually does. You can calculate that you've moved the equivalent of the pool's entire volume through the system and still have areas of poor mixing, And that's where algae often gets an opportunity. Not because circulation creates algae, because circulation is part of how we deliver the control mechanism. Remember the sourdough starter? If you've got warm water, nutrients, sunlight, and an area where effective sanitation conditions aren't being maintained, you've created opportunity.
Jason:That's another one I hear. My pump runs twenty four hours a day. Okay. That tells me the motor was operating for twenty four hours. It doesn't tell me that every part of the vessel was receiving effective circulation, especially today with variable speed pumps.
Jason:Running longer at lower speeds can be tremendously energy efficient. That's one of the major advantages of variable speed equipment. But operating time alone doesn't answer every hydraulic question. What is the actual flow? What's happening at the returns?
Jason:How are those returns aimed? What's happening across steps and benches? What's happening in the awkward corner that always seems to get dusty? What's happening in the filter? A running pump doesn't automatically equal a well circulated swimming pool.
Jason:Just like a chlorine reading doesn't automatically equal effective sanitation everywhere in the vessel. And now we have to walk into the backroom of our liminal warehouse because here's where we've been throwing boxes for years, the filter. Take an old sand filter. There may be 300, 400, 500 pounds of media sitting inside that tank depending on the size of the filter. That's an enormous amount of surface area.
Jason:And over the years, the filter has processed water containing everything the pool has encountered. Dirt, organic material, dead algae, oils, scale, debris, and, yes, the biological contribution of everybody who's ever gotten into the pool. You could jokingly say that an old filter contains the biological resume of every family member and friend who's ever stopped over. Not literally. Every microorganism from every swimmer forever.
Jason:Chlorine, backwashing, biological competition, and time take care of plenty. But the points remain. The filter is part of the water treatment environment. It isn't just an invisible box that magically makes dirt disappear. Organic material can accumulate.
Jason:Biofilms can form on surfaces. Media can become fouled. And as equipment ages, surfaces can become rougher, scaled, scratched, cracked, or otherwise more capable of retaining material than the smooth surface they started with. Think about a brand new cutting board compared with one that's been used every night for fifteen years. Same general object, very different surface.
Jason:So when someone tells me, I shocked the pool, why does this problem keep coming back? One of the questions I wanna know is, did we treat the swimming pool, or did we treat the entire water treatment system? Because if you've got a pristine looking vessel connected to a biological landfill in the equipment area, we've only addressed part of the problem. Phosphates have become one of those subjects where people tend to divide themselves into camps. One group acts like phosphate is the root of every evil ever committed by algae.
Jason:The other acts like phosphate doesn't matter at all as long as chlorine is properly managed. Reality deserves a little more nuance. Phosphorus is a nutrient. Algae uses it. Reducing available phosphate can make conditions less favorable for growth, but phosphate management is not a replacement for proper sanitation.
Jason:If you have inadequate effective chlorine, don't expect a low phosphate number to magically make your swimming pool sanitary. Likewise, having excellent sanitizer control doesn't mean nutrients cease to exist. These are different tools doing different jobs. This is where I like separating the systems into categories. Sanitation controls organisms.
Jason:Nutrient management limits resources. Circulation distributes treated water. Filtration captures material. Physical removal gets material out of the system. Those aren't interchangeable.
Jason:And that's why the dead algae conversation matters. Algae uses phosphorus while it's growing. Kill the algae, and you've stopped the current biological activity. But if all that dead organic material remains in the system and breaks down, some nutrients can be recycled. You didn't manufacture phosphorus by killing the algae.
Jason:You changed where some of the phosphorus was stored. Back to the warehouse, the mattress leaked. No. You've completed one part of the job. This is where pool care gets overly simplified.
Jason:People think green pool, add chemical. Pool turns blue, problem solved. But ask yourself, where did the dead material go? Was it filtered? Was the filter cleaned?
Jason:Was anything vacuumed to waste? Was material physically removed from the vessel? What caused the sanitizing problem in the first place? What's the cyanuric acid? What was the free chlorine?
Jason:Was the circulation actually effective? Are we maintaining enough residual to deal with new contamination as it arrives? Because otherwise, we may have accomplished something very temporary. We killed the current population without changing the conditions that allowed the population to establish itself, and now we're surprised when it happens again. Let's knock down one more myth while we're here.
Jason:Copper. Copper based products can have genuine algicidal properties. That's real chemistry. But pouring increasing amounts of copper into a swimming pool is not a substitute for appropriate sanitizer control. Eventually, you're also creating the potential for metal related problems, staining, discoloration, surface issues, and suddenly you're treating the consequences of the treatment you used to treat the original problem.
Jason:Pool chemistry has a funny way of doing that, which brings us back to one of the larger ideas in this episode. Every treatment has consequences. Cyanuric acid protects chlorine from sunlight. Useful. But it also changes chlorine chemistry.
Jason:Phosphonate sequesterants help manage metals. Useful. But some can ultimately contribute phosphorus as they degrade. Chlorine kills and oxidizes necessary. But killing material doesn't necessarily physically remove that material.
Jason:Circulation distributes sanitizer, essential. But circulation also distributes whatever else is dissolved or suspended in the water. The swimming pool is a system, not a collection of independent bottles. Now let's get back to the headline. Summer heat fuels algae growth.
Jason:Sure. But I think a better way to say it is summer exposes marginal control. You've got hotter water, more intense sunlight, more swimmers, more sunscreen, more sweat, more organics, potentially greater sanitizer demand, possibly greater biological growth rates. Everything is leaning harder on the system. So a pool that was barely maintaining control in May can suddenly lose control in July or August.
Jason:The heat didn't reach down from the sky and paint the swimming pool green. It changed the operating conditions enough that a weakness became visible, and LG took advantage of the opportunity. If there's one thing I want you to take away from this episode, it's this. Microbes are inevitable. Growth is optional.
Jason:You're not trying to build a swimming pool that has never encountered an algal cell. You're trying to create a swimming pool where that algal cell arrives and thinks, this place is terrible. There's enough there's enough effective sanitizer. The water is properly circulated. The filtration system is doing its job.
Jason:The system isn't overloaded with untreated contamination, and the conditions necessary for rapid growth never get a chance to establish themselves. That's pool care, not sterility, control. Before we leave, let's turn the lights off in our strange nineteen seventies warehouse. We've got the waterbed mattresses. Some things are incorporated into biological material.
Jason:We've got fluorescent tubes. Some things are being chemically controlled or sequestered. Some containers break down quickly. Others take time. Sunlight can degrade things.
Jason:Oxidation can transform things. Biology can decompose things. Changes in water chemistry can destabilize things. And then somebody puts a quarter in the machine and circulation distributes everything that's available. But through all of that, remember, change isn't removed.
Jason:Contained isn't removed. Dead isn't removed. Captured isn't removed until someone cleans the filter. Eventually, if you actually want something out of the warehouse, somebody has to carry it through the door. And maybe that's the mistake we make when we talk about swimming pool chemistry.
Jason:We spend an awful lot of time talking about what we're adding to the water. Maybe we should spend a little more time asking, what are we actually taking out? So the next time somebody tells you that their pool turned green because it got hot outside, don't immediately reach for another bottle. Ask a question. What changed?
Jason:What's the cyanuric acid? What the effective chlorine situation? Is treated water actually reaching the entire vessel? What's sitting inside the filtration system? What nutrients and organics are cycling through the water?
Jason:And did we solve the underlying condition, or did we just kill what was visible? Because before you ask what chemical kills algae, you should probably understand why the algae was able to live there in the first place. And that's where we'll leave it.
Spyder:This podcast is for educational and informational purposes only. It is not legal advice, and it is not site specific engineering, code, or safety determination. All field conditions should be evaluated in context. Thanks for listening to the Pool Envy Podcast, where licensed pool professionals speak up. Hosted by Jason Davies, licensed across Wisconsin, Florida, and Texas.
Spyder:For more insights, subscribe and join us next time.