The One on pH

In this episode of the Talking Pools podcast, Rudy Stankowitz dives deep into the essential aspects of pool water chemistry, focusing primarily on pH. He emphasizes the importance of understanding pH as the core of water chemistry, explaining how it influences chlorine effectiveness, the role of alkalinity, and the buffering systems that stabilize pH levels. Rudy discusses the impact of electrolysis, CO2 behavior, and the Langelier Saturation Index on pH management. He also highlights the challenges of accurate measurement and the biological influences on pH. The episode concludes with practical takeaways for pool professionals to master pH control and maintain balanced water.

takeaways

• pH is the most influential factor in pool water stability.
• Understanding pH requires knowledge of its dynamic nature.
• Alkalinity acts as a buffer to stabilize pH.
• Cyanuric acid and borates play crucial roles in pH management.
• Electrolysis in saltwater pools consistently raises pH levels.
• CO2 behavior is central to controlling pH fluctuations.
• The Langelier Saturation Index is heavily influenced by pH.
• Accurate measurement of pH is essential for effective pool management.
• Biological factors can cause local pH variations in pools.
• Maintaining balanced water reduces the need for constant chemical adjustments.

Sound Bites

• "Your job is to conduct, not to fight."
• "Balanced water is calm water."
• "pH is the heartbeat of the pool."

Chapters

00:00
Introduction to Flock It Friday and Industry Talent

01:43
Back to Basics: Understanding Water Chemistry

02:53
The Importance of pH in Pool Water

08:01
Understanding pH Measurement and Its Implications

09:20
The Carbonate System and Its Role in pH Stability

17:47
The Role of Cyanuric Acid and Borates in pH Management

23:48
The Interplay of pH, Chlorine, and Water Chemistry

28:33
Electrolysis and Its Impact on pH Levels

30:36
Equilibrium and the Dynamics of CO2 in Water

31:56
Biological Influences on pH and Algae Management

39:54
Advanced Oxidation Processes and pH Dynamics

40:49
The Langelier Saturation Index and Its Relationship with pH

41:50
Understanding pH and Water Chemistry

45:20
The Role of Carbon Dioxide in pH Control

49:11
The Impact of pH on Scaling and LSI

50:05
Total Dissolved Solids and pH Readings

51:42
Buffer Systems: Bicarbonate, Cyanuric Acid, and Borate

54:06
Turbulence and Gas Transfer Dynamics

55:08
Salt Systems and pH Drift

56:13
Biological Influences on pH

58:12
Radical Reactions and pH

59:23
The Relationship Between pH and Metals

01:03:11
Practical pH Management Strategies

01:07:02
Mastering pH Control in Pool Chemistry

Transcript

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SPEAKER_03 0:53

All right, Pool Talkers, you know what day it is. It's Flocket Friday here on the Talking Pools podcast with me, Rudy Stenkowitz. Now, before we cannonball straight into the deep end and smack the nuts of today's topic on the way down, let me just take a second to say holy chlorine tablets, Batman. We have heard from all of our Mentor of the Year nominees, and I've got to say, wow. I mean, talk about raising the bar. We've got some of the most brilliant, innovative, and straight up fan fucking tabulous minds in the pool industry represented this year. You people are proof that this industry is loaded with talent and heart. And if you've been listening these past weeks, you already know exactly what I mean. Right now we're in the final stretch, the home stretch of home stretches. I am knee deep in last-minute scrutiny of every candidate, digging through interviews, checking notes, and basically splitting pool hairs at a molecular level, because this belt, this championship belt, has to go to the best of the best. And sometime this month, I will appear like I dream a fucking genie, boom, smoke, sparkle, and all, right on someone's front porch, championship belt in hand, ready to crown the 2025 Talking Pools Podcast, pool industry mentor of the year. But while that's happening, while the suspense builds and you all keep hitting refresh on your feeds, I thought this would be a perfect time to get back to basics. You know, strip it down to what really, really matters, the stuff that started it all for most of us. The chemistry. Yeah, gonna go old school for a few weeks. We're taking the scenic route through water chemistry in an order that actually makes a lot of sense. No bouncing around, no half answers, no quote this week, and we sort of talk about chlorine again and quote, nope. We're gonna get structured, logical. One topic is gonna flow into the next, just like it should. Each Friday, I'm taking you on what I'm calling the sole train of pool water chemistry. We're starting with the heart of water, pH, and we're gonna ride this train straight through every major concept that makes pool water behave. Acidity, alkalinity, sanitizers, oxidation, buffering, balance, everything. Because let's be real, most of the confusion out there, most of the service headaches, the green pools, the cloudy water, the calls that make you want to throw your test kit in the middle of the friggin' street, it all circles back to water chemistry. And at the root of all of that chemistry, pH. So today we start right where it all begins with pH, the single most misunderstood, most influential number in your pool. If you think you already know everything about it, I promise you, by the time we're done, you're gonna look at that little seven-point something on your test block or in your spin touch with a whole new level of respect. So sit back, strap in, and grab your coffee, whatever your Friday ritual is, because this episode is the kickoff to our full chemistry journey. This is the one that's gonna set the tone because, well, pH.

SPEAKER_07 4:15

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SPEAKER_03 6:04

When we talk about pH in pool water, we're not talking about a number that sits on a strip. We're talking about the single most powerful, most misunderstood, and most influential factor that decides whether your pool is stable. Your chlorine is working, your plaster is happy. It's the boss of the pool. Everything else, sanitizer levels, alkalinity, calcium, temperature, they all play on the same team. But pH is the coach. It calls the shots, and when it drifts, the whole chemistry game changes. Now, we all learned early on that pH is a measure of how acidic or basic the water is. Seven is neutral, less than seven is acidic, higher than seven is basic. But here's where most people stop. The truth is pH is a living measurement. It's the pulse of your water, a real-time signal of how hydrogen ions are behaving inside an invisible web of chemical reactions. It's not a number on a chart, it's a dynamic indicator of equilibrium. The balance between acid and base forms of multiple systems all working at once. In pool water, that equilibrium involves the carbonic acid and bicarbonate system. The chlorine species, cyanuric acid, borates if you use them, and everything that's breathing, heating, splashing, or aerating that water, it's all in flux. That's why the same pool can test 7.6 in the morning and 8.0 in the afternoon, even though you didn't add a drop of anything. First thing to understand is that pH is not linear. The scale is logarithmic. That means every time pH changes by one number, the concentration of hydrogen ions changes by 10 times. That's massive. It's why small pH drifts can create huge changes in sanitizer strength or corrosion potential. And since we're talking about sensitivity, temperature plays a sneaky role here too. When water gets warmer, its natural balance point shifts. At 90 degrees, what we'd call neutral water isn't at a pH of seven anymore. It's closer to six and a half. So a hot spa isn't as acidic as it looks on paper. In fact, it's right where it should be. Same chemistry, different context. That's why you can't take cold water textbook values and apply them blindly to heated systems. This is where cold plunges are such a mystery to the people that are operating them. We're not trained in maintaining bodies of water that are 50 degrees or less. Now I know pool pros love numbers, and if you're using some type of a probe to get your readings, here's what you need to understand. You're not actually reading pH. What you're actually reading is electrical potential, not hydrogen concentration directly. That probe in your tester is a tiny voltage meter comparing hydrogen activity inside a glass membrane to a reference solution. It follows what's called a NERNST response. The steeper the slope, the more accurate the reading. But if that electrode's dirty, if the junction's fouled, or if the calibration's off, you're not reading pH. You're reading wishful thinking. Ionic strength changes how freely ions move. High salt means more electrical shielding, which makes the hydrogen ions look slightly weaker. In practice, that means that a salt pool might show a pH of 7.6, even though chemically it's acting more like 7.5. It's a tiny difference, but when you're balancing high-end systems or troubleshooting strange corrosion, it matters. So let's talk about what really drives pH in a pool, the carbonate system. That is the engine that stabilizes your water and it's built around carbon dioxide, carbonic acid, and bicarbonate ions. Together, they make up what we call total alkalinity. Your water's ability to resist a sudden pH change. So think of alkalinity as shock absorbers for your pH. Too soft, every bit of acid slams the pH down, too stiff, and the system bounces back upward with every aerated splash. When you add the acid to the water, those hydrogen ions look for something to neutralize. Bicarbonate steps in, grabs that acid, turns it into carbonic acid, which quietly breaks apart into CO2 gas and water. The gas leaves the pool, the water stays, and the pH barely budges. That's buffering. It's not magic, it's just chemistry keeping you out of trouble. But that same system can turn on you because when water moves, when it's air-rated or warm or turbulent, carbon dioxide escapes faster. Every CO2 molecule that leaves the pool takes a little acidity with it. The system reacts by pulling more hydrogen ions out of solution to replace the lost gas. Fewer hydrogen ions means higher pH. That's why your spa climbs in pH every day. Why fountains and spillovers love to drift upward, and why the best balanced pool slowly creeps toward eight point something if you don't keep an eye on it. So the rule is simple. Anything that increases aeration increases pH rise. High alkalinity makes it worse. Warm water speeds it up, and turbulence guarantees it. That's not poor maintenance, that's physics. Now, here's where smart techs take control. If you want to slow the upward drift, you lower the total alkalinity. For years the industry has pushed 100 to 120 parts per million because trichlor tabs were feeding acid into the pool. But in today's world, liquid chlorine, calhypo, salt cells, our problem isn't a pH that's dropping, it's a pH that's climbing.

SPEAKER_06 12:15

Today we're talking about the chemicals we use to raise or lower pH in swimming pool water and what each one does. We'll go through them one at a time, nice and simple. Let's start with raising pH. The first chemical is soda ash, also known as sodium carbonate. This one raises both pH and total alkalinity. If you want to bump your pool's pH up by about two tenths, you'd add around six to eight ounces per ten thousand gallons of water. For a four tenths jump, it's about twelve to sixteen ounces. Always dissolve soda ash in a bucket of pool water first, then pour it into the return flow so it mixes in evenly. It might make the water look a little cloudy for a short time. That's normal. Next up is borax, which you might recognize from laundry detergent boxes. In pools it's called sodium tetraborate, and it raises pH too. But here's the cool part. It doesn't raise total alkalinity as much as soda ash does. For a two tenths pH increase, you'll need about twelve to sixteen ounces per ten thousand gallons. For a four tenths increase, about twenty four to thirty two ounces. If any crystals don't dissolve right away, just rinse them in with pool water. Borax is great when you want a gentler adjustment. The third chemical is caustic soda, also known as sodium hydroxide, or lye. This one is strong, it gives a powerful pH boost without changing alkalinity much. If you want to raise pH by about two tenths, you'd use roughly six to ten fluid ounces per ten thousand gallons. For four tenths, about twelve to twenty ounces. You always want to predilute this chemical in a bucket first, add it slowly into the deep end. And make sure you're wearing proper protective gear like gloves and goggles. It can splash and it's very caustic, so handle with care. Now we've got baking soda, which is sodium bicarbonate. You probably have this one in your kitchen. It's mostly used to raise total alkalinity, not so much pH. It'll move pH just a little bit, but not enough to fix low readings by itself. If your alkalinity is low, say under sixty or seventy parts per million, you can add about one point four pounds of baking soda per 10,000 gallons to raise it by about 10 parts per million. Just remember, baking soda is for alkalinity, not for a quick pH fix. Okay, now let's switch gears. We've talked about how to raise pH, so let's look at how to lower it. The most common chemical for lowering pH is muriatic acid, which is a diluted form of hydrochloric acid. This one lowers both pH and total alkalinity. To drop your pH by about two tenths, you'd add around 10 to 12 fluid ounces per 10,000 gallons of water. If you need a bigger change, around 4 tenths, that's about 20 to 24 ounces. Always predilute muriatic acid. Mix one part acid with ten parts water, and pour it in front of a return jet while the pump is running. Never add acid with the pump off, and make sure the area is well ventilated because the fumes are strong. Another option is dry acid, which is sodium bisulfate. It comes in powder form instead of liquid. Just like muriatic acid, it lowers both pH and total alkalinity. To lower pH by about two tenths, you'd use roughly 12 to 16 ounces per 10,000 gallons. For a four-tenths drop, use around 24 to 32 ounces. You can sprinkle it across the deep end of the pool and let it dissolve. But here's an important note Avoid using dry acid if your pool has a salt chlorine generator or natural stone surfaces, because it adds sulfates, and those can cause long-term damage. So to sum it all up, soda ash raises pH and alkalinity. Borax raises pH with a smaller alkalinity change. Caustic soda raises pH strongly. Use with care. Baking soda raises alkalinity mainly, with just a small pH effect. Muriatic acid lowers both pH and alkalinity. Dry acid does the same thing, but adds sulfates. Always remember, add chemicals slowly, measure carefully, and give to the water time to circulate before retesting. Pool chemistry is a balance. You want to nudge it, not shock it. And that's how we safely adjust and control pH in pool water.

SPEAKER_03 17:02

In today's world, liquid chlorine, cal hypo, salt cells, our problem isn't a pH that's dropping, it's a pH that's climbing. And by bringing the alkalinity down to around 60 parts per million, you reduce the bicarbonate concentration and cut the fuel that feeds the carbon dioxide loss. It's like turning down the burner under your pH pot. Less bicarbonate means less carbonic acid, which means less CO2 to escape, and less reason for the pH to rise. And don't worry, 60 parts per million is still plenty of buffer. You're not leaving the pH unprotected. You're just dialing in the balance between stability and mobility. You want the pH steady, not stubborn. High alkalinity makes the pH stubborn. But total alkalinity isn't the only player buffering your water. Let's bring in cyanuric acid. Most people think that it's just a chlorine stabilizer, but it is also a weak acid with multiple proton sites that can grab or release hydrogen ions. So in practical terms, that means it acts as a secondary pH buffer, especially against the downward drift. When you add acid or when trichlor dissolves, cyanuric acid absorbs some of that shock. Again, we're not talking actual shock, we're talking our shock absorbers, in preventing the pH from nosediving. It's subtle but important. In a stabilized pool, part of your measured alkalinity actually comes from cyanurid ions. That's why the test kit tells you to correct total alkalinity when you have a CYA level in the water. Roughly one-third of the cyanuric acid concentration shows up in your alkalinity number. So if you've got 50 parts per million of CYA, think about 16 of that as being fake alkalinity. It's cyanurate alkalinity, not carbonate. The pool doesn't care what label you give it, but your LSI calculation sure does.

SPEAKER_06 19:04

Now here's something a lot of people don't realize. We call this reaction kinetics, which is just a fancy way of saying how fast or how well a chemical reaction happens. Let's go through a few examples so you can see what I mean. First up, phosphate removers, like lanthanum chloride. These work best when the pH is right around 7.2. At that level they form nice solid particles that can be trapped in the filter or vacuumed out. If the pH is too high or too low, those particles don't form properly, and the phosphate remover won't work as well. Next, polyquat algecides. These are non-metallic algicides that are great for preventing growth, but they break down faster when the pH gets too low. So if your water is more acidic than normal, that algacide doesn't last as long, and you'll have to add more to get the same effect. Now let's talk about MPS, or nonchlorine shock. This product works best when the water is near neutral, about 7.2 to 7.4. At that range, it oxidizes organic waste efficiently without producing unwanted byproducts. If the pH is way off, it just can't perform at full strength. And then there are metal sequestrants. These are the chemicals we use to keep metals like iron and copper from staining surfaces. When the pH goes above 7.8, those sequestrants can start to fall apart. The chemical bonds that hold the metals in solution weaken, and the metals can drop out and cause stains or discoloration. So the big takeaway is this. Every chemical you use in a pool, from phosphate removers to shocks to algae, has an ideal pH zone where it performs best. If you're outside that zone, you're wasting money and effort because even the best products can't work properly when the water's chemistry is off balance. It's not just about the LSI, it's about pH, the master control knob for how all those reactions happen in your pool water.

SPEAKER_03 21:25

When you establish a borate level around 30 to 50 parts per million, you give the water an entirely different buffering system, one that works in the opposite direction of alkalinity, whereby carbonate and cyanurate mainly resist acid and downward movement. Boreates resist base and upward drift. So when the pH tries to climb, boric acid knocks its ass back down. How does it do that? Well, it quietly reacts with the extra hydroxide ions that are pushing it upward, neutralizing them before they can do any real damage. Realistically, what they're doing is converting themselves to be something else with that hydroxide ion. So it's not like alkalinity where total alkalinity gets used up when you add acid, which is why when you add acid to lower pH, you will always also lower total alkalinity no matter how you add it. But borates work a little bit differently. They don't get used up, they become something else that actually still is a buffer against an upward drift in pH. So that borate buffering system is permanent unless you physically dilute the pool. That's why once you set your borate level, your acid demand usually drops by half. The pH stops trying to escape. Borates also makes the water feel smoother. It inhibits algae and even inhibits slow corrosion in some metals. But chemically, their greatest trick is that they consume the very ions that cause the upward. Climb in the first place. That's why a borated pool feels calm. The chemistry isn't frightening itself. Not anymore. So picture this carbonate buffering catches you on the way down. Borate buffering catches you on the way up. And cyanuric acid fills in the gap in between. Together, they make a three-zone defense system that keeps your pH sitting steady in that 7-4 to 7-6 sweet spot where everything works right. That's where your chlorine is about two-thirds in its strongest form, hypochlorous acid. And one third in its weaker, ionized form. Below that, it's aggressive. Above that, it's lazy. And remember, as pH rises, chlorine loses its bite. At eight, only about a fifth of your free chlorine is active sanitizer. At nine, it's almost useless. And if you're running a high pH with cyanuric acid, you're stacking two weaknesses on top of each other. That's why some clear pools still turn green. The chlorine's there, but chemically, it's taking a nap. There's another wrinkle here that rarely gets mentioned. Hypochlorous acid, the strong form of chlorine, actually bonds loosely to cyanuric acid, forming a protected but still available complex. Hypochlorate ion, the weak form that dominates at a higher pH, does not bond that way. It actually repels or peels away from cyanuric acid because they're both negatively charged. That means when your pH drifts high, not only do you lose chlorine strength, you also lose stabilization. Free chlorine peels away from its sunscreen and burns off in sunlight faster. That's a double whammy, weaker and shorter-lived sanitizer. I know there's a lot of stuff out there that says if you have a cyaneuric acid level in the pool, it really doesn't affect the chlorine's effectiveness because the cyaneuric acid already does. It doesn't mean it's keeping it at a high point and it's preventing it from getting weaker. It means that the cyaneuric acid has weakened the effectiveness of your chlorine so much that the change in pH doesn't really make that much of a difference anymore. It's kind of like kicking somebody when they're down. You can go over and do it, but you're not going to knock them down any more than they're already knocked down when they're laying on the ground when people stomping on their head. Now let's talk about measurement. You and I both know pH testing is one of the easiest things we do and one of the most often misread. Color blocks lie. If you're matching colors by eye, everybody sees color differently. Probes drift, and if you're not calibrating, you're basically guessing. Every pH probe works again by generating a small voltage difference. That voltage changes with hydrogen activity, and that change should be about 60 millivolts per pH unit at room temperature. If your probe's old, coated in oil, or you store it dry, that slope drops. Suddenly, seven and eight look almost the same. That's how people chase phantom problems that don't exist. And the irony, the higher the TDS, the more the probe stabilizes because ionic conductivity improves. So the very salt that complicates your chemistry makes your reading more stable. But that same salt also changes the activity coefficients, meaning your numbers right, but the chemistry underneath it is slightly different. You have to interpret results in context. Now, if we want to get into what else pushes pH around beyond gases and buffers, we've got to talk about electrolysis.

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SPEAKER_01 28:01

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SPEAKER_03 28:31

In saltwater pools, your generator is doing two things at once. Making chlorine at the anode and creating hydroxide at the cathode. That hydroxide can bond with the sodium from the sodium chloride that you added to get that chloride level to make chlorine gas in that salt cell in electrolysis. So now basically sodium hydroxide, that's caustic soda, or sometimes we call that lye. It's one of the most base materials we know of on the planet. Now that mixes back into the pool and bumps your overall pH upward. Everything that passes through that cell is subject to electrolysis, including water. So H2O, when it passes through, it becomes hydrogen and hydroxide. The hydroxide we just spoke about, we end up with caustic soda, jacks the pH. The hydrogen ion bonds with another hydrogen ion, becomes hydrogen gas, and that bubbles off. That constant bubbling inside the cell is creating turbulence. The turbulence is causing the aqueous carbon dioxide in the solution to out-gas, and that too driving your pH upward. So even if you control every other factor perfectly, electrolysis ensures you'll have a gentle, consistent nudge toward a higher pH. That's why salt systems always seem to want to run high in pH, that is. It's not imagination, it's cell physics. Heaters and return lines add their own quirks. Heat drives CO2 out of the water faster, so warm water needs more acid attention. High flow through fittings and spa jets that accelerates aeration. Even the shape of your pool matters. Shallow pools with lots of surface area lose CO2 faster than deep, still bodies of water. Every design decision changes the pH behavior even before a single chemical hits the water. Now let's take it even deeper. All of this chemistry happens in what we call equilibrium. That's a balance point that can shift but always seeks stability. The rate at which CO2 escapes from water to air is proportional to the difference between how much CO2 the water has and how much the air can hold. The bigger that difference, the faster it leaves. That's why newly filled pools with high alkalinity outgas like crazy for the first few days. They're super saturated with CO2. Once they breathe down to atmospheric levels, the pH stabilizes. So when you lower alkalinity, you're not just reducing buffering, you're also reducing that carbon dioxide reservoir, shrinking the pressure differential that drives off gassing in the first place. It's double reinforcement. That's why modern techs who run pools at a target alkalinity of 60 parts per million with borate around 40 see their pH drift slow, like a crawl instead of a run. Another subtle piece of this puzzle is measurement temperature. Because both the electrode and chemical equilibria respond to temperature, readings taken in cold water may look higher than the real value. Warm water compresses the pH scale, cold water stretches it. So if you're balancing in winter and the water's 50 degrees, don't be surprised if the pH bounces a bit when spring arrives. Now, we can't talk pH without acknowledging the biological side. Algae and bacteria actually influence pH locally. During the day, photosynthetic organisms pull carbon dioxide out of the water, which raises the pH right at their cell surface. At night, they respire and release CO2, which lowers it again. That creates microscopic pH swings even when the bulk water looks stable. And inside biofilms, those slimy coatings you sometimes find in lines or on ladders, the pH can be a full unit higher than the surrounding water. And that matters because it makes those zones perfect breeding grounds for resistant species like black algae, which we know from my research back in 2018 is cyanobacteria. High pH microenvironments strengthen those films across linking the protective polymers that chlorine struggles to penetrate. So when you're fighting stubborn growths, you're not just fighting biology, you're fighting local pH chemistry. Managing your bulk pH between 7.4 and 7.6 helps minimize those high pH pockets.

SPEAKER_00 33:00

Since 2018, Rudy Stankowitz has been at the forefront of groundbreaking research in swimming pool microbiology. Known across the pool industry for his deep expertise in water chemistry, Rudy became the first person to correctly identify what is commonly known as black algae as cyanobacteria, a discovery that completely changed how professionals understand and treat these stubborn growths in pool environments. Following that discovery, Rudy began cultivating and studying live cultures of the exact cyanobacteria and diatom species found in swimming pools across the United States. In doing so, he became what he describes as an algaculturist, someone who grows and observes algae and cyanobacteria under controlled conditions to understand their behavior and resistance. To date, Rudy remains the only individual in the swimming pool industry, including all chemical manufacturers, who works directly with the same living species that colonize real swimming pools. His hands-on research gives him unique insight into how these organisms grow, adapt, and survive despite modern pool sanitization practices. His work began with the collection of dime-sized black algae specimens from a public swimming pool in Gainesville, Florida, a site labeled Gainesville A in his study. Microscopic examination revealed that these samples were not a single type of organism as previously assumed, but instead thick matted colonies composed of multiple genera of cyanobacteria intertwined together. The most prevalent were oscillatoria, microcoleus, and nostalg, all filamentous, thread-like cyanobacteria capable of forming dense mats on pool surfaces. Rudy's team then collected additional samples from another recreational water facility located roughly 100 miles away in Atlantic Beach, Florida. This time the composition was entirely different. The Atlantic Beach specimens lacked the nostalgic, microcoleus, and oscillatoria found in the Gainesville Ace samples. Instead, they were dominated by a filamentous cyanobacterium known as Leptolingbia. This variation was a key discovery, showing that the microbial makeup of swimming pool black algae can differ dramatically across relatively short geographic distances, in this case, only about 100 miles. That finding alone demonstrated that black algae is not a single organism, but rather a community of cyanobacteria that varies with environmental conditions such as sunlight, water source, and local chemistry. Further microscopic analysis revealed even more complexity within the sticky mucus-like layer of the cyanobacterial mats, known scientifically as exopolis saccharide. Rudy identified several species of true algae living inside. These eukaryotic algae were taking shelter within the biofilm matrix produced by the cyanobacteria. This discovery led Rudy to describe black algae not as one organism, but as a collective cyanobacteria community, a biological partnership where cyanobacteria are dominant, but other algae coexist within the protective biofilm. To test whether this community could produce toxins, samples from a third site, Gainesville Bee, located within one mile of the original Gainesville pool, were collected and analyzed. Like the Atlantic beach samples, the Gainesville Bee colonies were dominated by leptolingbia, but also contained oscillatoria and cynecococcus. Before testing, chlorine in the water was neutralized with ascorbic acid, vitamin C. Laboratory analysis using an enzyme-linked immunosorbent acid, ELISA, detected trace amounts of microcystin, a toxin produced by some cyanobacteria. The measured level, 0.08 nanograms per milliliter, was extremely low, far below both the EPA drinking water health advisory limit of 1.6 micrograms per liter and the benchmark of 0.15 parts per billion. This finding confirmed that while swimming pools cyanobacteria can produce toxins under certain conditions, the levels found in properly managed pools are well below health concern thresholds. To document his findings, Rudy used advanced microscopy techniques, including phase contrast and epifluorescence imaging with a Nikon Eclipse Ty S inverted microscope. This allowed his team to observe the fine structure of each colony, identify the specific filamentous cyanobacteria present, and capture detailed micrographs for analysis. The implications of this research are significant. For decades, the pool industry treated black algae as a simple plant-like nuisance, something to be brushed off and shocked away. Rudy's work showed that it is actually a complex layered biofilm made up of multiple cyanobacteria species, organisms that are far more resistant to sanitizers because of the thick protective coating they create. Understanding this has changed how pool professionals approach treatment and prevention strategies, shifting the focus toward biofilm disruption and improved circulation instead of relying solely on high chlorine doses. Perhaps most importantly, Rudy's findings demonstrate that the composition of cyanobacterial communities varies by region. A black algae sample from Florida may contain entirely different species than one from Arizona or California. This suggests that geography, climate, and local water chemistry all influence which organisms dominate a pool's microbial ecosystem. In short, Rudy Stankowitz's research redefined what the pool industry thought it knew about black algae. He proved that what professionals were fighting wasn't a single species of algae, but a cooperative colony of cyanobacteria and true algae living together inside a self-made biofilm. His continued cultivation of these exact species in laboratory settings allows him, and by extension, the entire pool industry, to better understand their biology, resistance mechanisms, and the most effective ways to control them. Rudy's work bridges microbiology and the swimming pool trade in a way no one else has done before. By identifying black algae as cyanobacteria and classifying it as a collective cyanobacteria community, he opened the door to a new era of pool science, one where treatment is based on biological understanding, not just chemical reaction.

SPEAKER_03 39:33

Let's also talk about advanced oxidation and how pH ties into that in ozone or hydroxyl radical systems. pH affects both the rate and the strength of oxidation. At a higher pH, you get more radical generation, but a shorter radical life. Why? Because bicarbonate and carbonate ions actually quench radicals, converting them into weaker forms like carbonate radicals. Those still oxidize, but far less aggressively. So if you're running AOP or ozone and wondering why the kill rates drop when the pH rises, that's why. Your radicals are getting tamed by the very buffering ions you rely on for stability. It's a balancing act. And since we're talking about balance, let's not forget the LSI, the Langolier Saturation Index. That's the tool everybody uses to measure scale and corrosion risk. LSI depends heavily on pH. And because pH is logarithmic, small movements make big changes. A jump of just three-tenths in pH doubles your scaling tendency. That's why chasing LSI purely through alkalinity or calcium is short-sighted. pH moves the needle faster than anything else, but LSI only tells you about calcium carbonate. pH also controls the solubility and oxidation of metals. And LSI doesn't talk about that. Low pH dissolves copper and brass. High pH drops metal oxides and stain surfaces. And because cyanuric acid and sequestrants both interact with metals differently, depending on pH, managing pH precisely is your best defense against staining and heater damage. Andrea talked about metal stains a couple of weeks ago. Great episode on Tuesday. Tons of information. I think it was called Metal Menace, if you look back through. Another one that you should definitely check out. So measurement precision matters here too. Even the best instruments over time, drift. If your pH readings are inconsistent, you could be chasing phantom LSI problems. Keep in mind, LSI is only about protection of the vessel, not water quality. Although a high calcium level or high LSI could give us hazy water. I mean, that's about the extent of it. The big concern is whether or not it's going to etch the plaster or it's going to scale the plaster. That's it. It's a small part of a big picture. So anyway, always calibrate. Always rinse your probes and remember that glass electrodes age. Replace them before they lie to you. Now, when you look at all of these systems together, carbonate, cyanurate, borate, you get what I call a pH envelope. And within that envelope, the water can absorb or release hydrogen ions without a major pH change. The wider the envelope, the more stable the system. But there's a trade-off. If you build the envelope too strong, say your alkalinity is at 120, it resists acid so well that every bubble of CO2 that leaves still pulls the pH up. Now you've got a freight train of drift. If you make it too weak, total alkalinity under 40 parts per million, pH is going to crash every time you sneeze near the acid bottle. So 60 parts per million for total alkalinity, cyanuric acid at 50, borates at 40 parts per million, that's got Goldilocks saying fucking A. Enough buffer on both sides, minimal gas loss, low acid demand, maximum chlorine efficiency, and don't underestimate the role of turbulence. Jets, fountains, bubblers, they're gorgeous. They are, but they are pH accelerators. They strip CO2 like soda fizzin out of a can. That's why spas and therapy pools are the toughest pH cases in the business. The combination of heat, agitation, and high alkalinity is a perfect storm for a constant pH rise. Lower the TA, use borates, point those returns downward. That's how you tame that beast. Another advanced concept most people overlook is that pool water isn't ideal from a chemistry standpoint. Every dissolved ion changes how every other ion behaves. That's what scientists mean when they talk about activity coefficients. In our world, it means your pH reading is at best an estimate. High TDS changes ion interaction. So the real chemical reactivity can differ slightly from what your test says. But for practical purposes, as long as you understand the direction of drift and what's causing it, you can control it. And if you want to get really technical, even your pH electrode measures voltage based on hydrogen ion activity compared to a reference solution. Temperatures affect that voltage response. That's why good meters have an automatic temperature compensation. It's not a luxury feature, it's chemistry insurance. Without it, a change of 10 degrees can shift your apparent pH by a couple of tenths. At this point, you're probably noticing a pattern. Every process that changes pH involves either adding or removing hydrogen ions. And in pools, that mostly means moving carbon dioxide. So in practical terms, controlling pH is about controlling CO2 behavior. The rest, acids, bases, buffers, those are just the tools we use to steer that gas equilibrium. When we look at the behavior of carbon dioxide, I mean that's that's the heart of it. That's the heart of really what we're dealing with in pH control and pool chemistry. I mean, think of carbon dioxide as the puppet master, pulling the strings of your pH. The more it leaves the water, the higher your pH goes, the more it dissolves back in, the lower your pH drifts. Every chemical you add, every piece of equipment you turn on, every bubble that breaks the surface, it all plays a role in that dance. Now, in the real world, turbulence isn't something you can avoid. Pools are meant to move. They circulate, spill over, aerate, splash, they breathe. That's the point. Stagnant water is dead water. But what you do is design and operate in ways that minimize unnecessary CO2 loss. When you point returns downward instead of breaking the surface, when you manage flow through therapy jets or features with moderation, when you balance temperature and alkalinity together, you're controlling the chemistry before it becomes a problem. That's what separates a seasoned tech from someone just dumping acid in twice a week. It's not just numbers. It's not okay just to balance your saturation index with your pH high. That's not a good thing. There's a lot of other things that your pH affects, and we just went through a lot of them. Not all of them, mind you, there's more. LSI is just a small part of what we do. There are ranges, acceptable ranges, and ideal ranges for each of these parameters, and I know some folks call it range chemistry, so be it. There's a reason those ideal ranges exist. They look at the big picture. It's not just numbers, it's the living chemistry of what we do every single day. That said, I'm Rudy Stankowitz. This is the Talking Pools podcast. Until next time, which will be a conversation on total alkalinity. Be good. Be safe.

SPEAKER_05 47:19

Right. Right. Right.