Microns & PPM: The Invisible World Inside Your Pool

Ever wonder why your pool still looks hazy even after a long vacuum session? We unpack the tiny measurements that control big results: microns, which decide what your filter or cleaner can actually catch, and parts per million, which reveals how little chemical is truly in the water. With clear examples and real‑world comparisons, we connect the dots between filtration performance and precise dosing, so you can stop guessing and start dialing in clarity.

We break down filtration by what it really removes. Sand typically captures 25–30 microns, cartridge around 10–20, and DE as fine as 1–3. That matters because the human eye only sees down to roughly 35 microns, so much of what irritates owners is invisible unless your equipment can trap it. You’ll hear practical guidance on vacuum system bags (60 vs 200 microns), why pollen and algae dust pass through the wrong bag, and how robotic canisters vary—from Polaris “ultra fine” ranges to Dolphin fine filters reaching about 20 microns. We also spotlight a cartridge‑equipped vacuum solution that filters to 10–20 microns, a real upgrade for routes with silt, DE dust, and heavy pollen.

Then we translate PPM into plain language. One PPM is like one minute in two years: tiny. We show why five PPM of chlorine is not a chemical bath in 15,000 gallons, and how low pH—not chlorine—often causes irritation. You’ll learn why the industry anchors dosing to 10,000 gallons, how 8.34 pounds per gallon of water drives the math, and how this standard turns messy calculations into simple rules of thumb. We share easy dosing examples for alkalinity and stabilizer, and point you to calculators that tailor doses to any pool size without mental gymnastics.

• what a micron is and why it matters
• human eye limits vs filter capture
• sand, cartridge, and DE micron ranges
• vacuum bags for leaves vs fine debris
• robot canisters compared for fine capture
• when to use suction, pressure, or robots
• bottom feeder cartridge option for dust
• what PPM means in real pool doses
• why 10,000 gallons standardizes dosing
•

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Transcript

Welcome And Micro World Setup

SPEAKER_00 1:02

Hi, welcome to the Pool Guy Podcast Show. In this episode, I'm taking you to the micro world, and I'm going to talk about parts per million in microns, and this is especially important in pool service where you're going to hear these these terms thrown around a lot out in the industry. Are you a pool service pro looking to take your business to the next level? Join the Pool Guy Coaching Program. Get expert advice, business tips, exclusive content, and get direct support. From me, I'm a 35-year veteran in the industry. Whether you're starting out or scaling up, I've got the tools to help you succeed. Learn more at swimmingpoollearning.com. I'll start off with the microns because it's a little bit easier to understand versus parts per million, which I'll get to later. And it takes a little bit of unpacking and why the term is used in the industry. Micron is simply a measurement of how small a particle is. And this is really important when you're talking about filtration for the pool, and also when we talk about vacuum systems and robotic pool cleaners. So let me just explain what a micron is. It's one millionth of a meter. So one micron is equal to 0.001 millimeters. To give you some context, the human hair is about 70 microns, and fine beach sand is about 90 microns. A grain of salt is about 100 microns. So we use microns for filtration because it's a pretty small particle and you get an idea of the filtration capacity of different filter types. For instance, a D filter will filter down to 1 to 3 microns, a sand filter will filter down to about 25 to 30 microns, and a cartridge filter is anywhere from 10 to 20 microns. I've heard sand filters up to 40 microns as well when they describe it. Because of the diatomaceous earth that coats the grids, it traps everything basically from going back into the pool. Cartridge filter is the second best, of course. And sand filter is the third best filtration type out there. These are the primary filtration types that you're gonna find out in the pool industry. There really isn't much of anything. There's some hybrid systems like a quad D filter that uses a cartridge type D grid. And then you have different sand filter media as well. But sand is typically what's used, and that's what it's referred to as. So basically, the D filter again is the best, and you can't really see anything really above 30 microns. 35 microns is the largest particle that a human eye can see without magnification. So keep that in mind that even using a sand filter, you can't see anything that the sand filter doesn't pick up in the pool. Same with a cartridge filter, and especially with a D filter, so that can't be seen. Pollen is a little bit bigger, and then of course the human hair at 70 microns, and then table salt at 100 microns. So a micron is a very, very small measurement. And when you talk about vacuum system bags, this is where this comes into play. Also, robotic pool cleaner filtration systems, the micron definitely comes into play. I'll start with the vacuum system bags to make it easy. If you have a 60 micron vacuum system bag versus a 200 micron vacuum system bag, which one picks up the smaller amount of particles? And the answer is the 60 micron bag because that will filter down to 60 microns. This means that it'll trap everything in the bag and only let out whatever is not 60 microns or smaller in diameter or particle. So it'll capture, of course, since human hair is 70 microns, it'll capture human hair without it passing through the bag. Of course, it doesn't really pass through the bag because of the way the bag is designed, but that just gives you a visualization. It'll pick up salt because salt's 100 micron and it filters down to 60 microns. So it'll pick up salt in the bag without letting it back into the pool. But it won't pick up pollen because pollen is a smaller micron particle than 60 microns, so it'll pass right through the debris bag back into the pool. Nor it will pick up algae dust because algae dust is smaller in particle size, it's about I think 10 microns or so. So the algae dust will pass right back through the bag into the pool. So you kind of get an idea that even at a 60 micron dirt, small particles like pollen and then algae dust will pass right through the bag. And that's why when you're vacuuming a vacuum system bag in a pool, and maybe there's DE on the bottom, or there's some pollen or dead algae, it'll go right through the bag and cloud at the pool. It's not really made to pick up anything less than than the 60 microns, and that's why a 200 micron bag won't pick up anything below that, and everything will pretty much pass through the 200 micron bag, and it's something that's used mainly for leaf debris, larger debris, and not necessarily to pick up the smaller particles. When you're talking about robotic pool cleaners, if you compare, for instance, the Polaris robotic pool cleaner debris canister with the dolphin filter canister, there is quite a difference in microns there. I believe the standard, although they don't list it, the standard debris canister for the Polaris cleaner is roughly about 100 microns, maybe 120 or so. And then they have a fine, ultra fine canister, which is about 70 microns, but I think it's a little bit better than that. I would say it's more like 50 microns, but they rate it at 70 microns. Whereas the dolphin cleaners, like for instance the Dolphin Liberty, they have a fine filter, which is basically a filter debris canister with a cartridge filter material on it, and this will filter down to about 20 microns. So that will pick up, of course, you know, almost everything in the pool. I find that it picks up the algae dust, the pollen, even though it says 20 microns, it does pick up the finer particles as well. As it cakes onto the cartridge material, it'll actually stay on there and not go back into the pool. So if you're looking at robotic pool cleaners and you want the filter down to say 20 microns, the dolphin cleaners do have that capacity with the fine filter, whereas the Polaris cleaners will filter down to, in my opinion, about 50 microns, which is something you can't really see anyway with the human eye. So the filtration is pretty close to each other, with the dolphin being finer. If you look at cleaners like iPair, they claim to filter down to 3 microns, which is possible with their filter canister, and it's one of those things where it's all relative to you know the fact that you can't see those particles anyway. And I would say that the Polaris cleaner with the ultra fine, the dolphin with the filter canister, and the apier cleaners all filter down to a good fine micron, and there's not a huge difference between those three, although the dolphin cleaner I would say would be the finer micron robotic pool cleaner versus the other robotic pool cleaners, barring other other manufacturers like IPier that will filter down to even a finer particle. You also see the micron rating in some robotic pool cleaners as a kind of like a UM, so that's one millionth of a meter, and that's kind of the kind of the scientific marking. It's not quite a typical U, but it's kind of like looks like a UM, and that's just one micron, or that's the micron rating. So if it says 70 um, that's 70 microns, just so you know. So just to recap, the smaller the micron, the better the filtration. So a 60 micron bag will filter debris down to 60 microns. So anything smaller than that will pass through the bag, and anything 60 microns and above will be trapped in the bag. So a lot of dirt, a lot of silt, a lot of the gunk in the pool is going to be captured by a 60 micron vacuum system bag, but other stuff will pass through that's not down to that micron level, that's a finer micron level, I should say. If you're wondering about the pressure side cleaners with the bag on top, the Polaris 280, the filtration of that is not quite as good. I think the Playeris 4 filters down to 100 microns, but those bags on top I would say are probably about 200 microns or so. They do make an ultra fine bag that's really good. I think that's about 100 microns. So the return side cleaners won't pick up dirt, and that's why you see a lot of dirt in the pool on the step areas and corners of the pool, because they're not designed for dirt, they're primarily designed for leaf debris, and that's why a suction cleaner is better for pools with a lot of dirt, because then you'll use the suction cleaner and it'll pick up all the dirt and go, it'll go into whichever filtration system you have attached to your pool and filter that out. And speaking again about the vacuum system bags and the microns there, one nice thing is the new bottom feeder cartridge filter assembly. It's the cartridge filter on top the bottom feeder or shrimp cleaner, which will filter down to 10 to 20 microns because it's basically just a cartridge filter on top of that vacuum system. And this is the only vacuum system that's actually designed now to collect dirt in the pool down to 10 to 20 microns. So if you're looking for a vacuum system that will capture debris down to 10 to 20 microns, which is dirt, pollen, algae, dust, diatomaceous earth in the pool, then the bottom feeder or shrimp with the cartridge filter assembly will do that. Again, the bags won't capture anything below their micron rating, it'll pass right to the bag back out into the pool. And this is why this cartridge filter assembly is really a game changer in the vacuum system industry. Let me switch over now to parts per million. This of course is a very small measurement because it is a parts per million. To give you an idea, two parts per million of chlorine seems like a lot of chlorine in a pool, but it's only two ounces of dry and about ten ounces of liquid chlorine in fifteen thousand gallons of water. Again, think about this for a minute. Two parts per million of chlorine in a 15,000 gallon pool is about 10 ounces of liquid chlorine or two ounces of calhypo or dichlorine in the pool. It's a very small amount in a large body of water, and this is where a lot of people kind of get confused when you say that the pool has five parts per million of chlorine. You know, you only have about 50 ounces of chlorine in that pool in a 15,000 gallon body of water, and it's not a lot of chemical in that water itself. And when people say that they have a reaction to chlorine, it's probably more or less a reaction to low pH in the pool because there is not much of a chemical in that much water. And here is one part per million compared to other measurements. You get an idea of how small one part per million is. It's one minute in two years, it's one penny and ten thousand pennies, and it's one inch and sixteen miles. So a part per million is a very, very small measurement. You could look at it another way here. One part per million is one part chemical per one million parts water. Again, that's why it's called parts per million because it's one and one million parts per water. So basically, three parts per million of chlorine means three milligrams per liter. One hundred parts per million of calcium hardness is one hundred milligrams per liter. So one gallon of water weighs eight point three four pounds, and this is gonna come into the equation in a minute here because we use ten thousand gallons of water as a standard measurement in pool chemistry, and you may wonder well why do we use 10,000 gallons of water? Not 15, why not 20? And why do we even have a standard? Well, the 8.34 pounds of water makes it possible to actually calculate standard chemical dosing, and this is what they put on the packaging of the bags and trichlor tablets, because you need some kind of standard for this to work because of the 8.3.34 pounds in one gallon. So a 10,000 gallon pool has 83,400 pounds of water. That's a pretty heavy pool. That's a lot of water, that's a lot of weight, by the way, in a pool if you ever think about it. So 10,000 gallons of water again has 83,400 pounds of water in it. So one parts per million in 10,000 gallons equals 0.0834 pounds or 1.33 ounces of pure chemical. Again, 0.834 pounds or 1.33 ounces of pure chemical. So this makes dosing easy. So you can really simplify the calculations because the 10,000 gallons really helps with breaking down the weight of the one gallon. So basing everything on 10,000 gallons of water eliminates doing a lot of complicated math, which we don't want to do in the pool industry. We just want everything simple. For instance, if you wanted to add sodium bicarbonate to raise the alkalinity in the pool, baking soda, we know that 1.5 pounds raises 10 parts per million and 10,000 gallons of water based on the calculations of the parts per million and the 10,000 gallons, the breaking up the gallon of water into that. So it's really easy to calculate that. So 7.5 pounds raises total alkalinity to by 50 parts per million in 10,000 gallons of water. If you have a 20,000 gallon pool, you just double the dosage. And of course, you can use online calculators to calculate dosing. It does all the math for you, it'll separate this for you in based on a 10,000 gallons formula. So I like the pool calculator.com. If you have a 14,000 gallon pool, it'll actually break it down for you based on that size of water, and you won't have to do any math. Again, there's no reason to do real math out there doing pool chemistry, but all these calculating apps that are available, you just put the amount of gallons of water and then what you want to raise or lower in the pool, toacolinity, pH, chlorine, and it'll actually calculate everything for you based on the 10,000 gallons of water formula. Again, standardizing this also makes it easy. For instance, cyaneric acid or stabilizer, if you wanted to raise it by 10 parts per million and 10,000 gallons of water, you would need 13 ounces, or 4 pounds of it will raise it by 50 parts per million. And again, this is all because we've standardized it to 10,000 gallons of water to make calculating things very easy in the industry. So one part per million is 0.0001% or.00001. So 10,000 parts per million is only 1%. It's a really small measurement. And again, if you're gonna have two parts per million of chlorine in a 15,000 gallon pool, it's only 10 fluid ounces of liquid chlorine in the entire body of water. So I hope after listening to this podcast, you know the micron sizes, kind of you get an idea that you know a grain of salt is 100 microns, and you have filtration depending on the filter, down to at least 30 microns with a sand filter, down to 5 microns with a D filter. And then you'll know more about parts per million. It's just a measurement based on 10,000 gallons of water to standardize dosing in the industry, and you can find all kinds of charts online with dosing charts with 10,000 gallons of water. Since it's standardized, you can actually add every chemical you can think of in the pool industry off of that 10,000 gallon chart using an app like the poolcalculator.com based on the size of your pool or the pools on your pool route, and you can get really good dosing, very accurate dosing measurements based on that. And it's really great to have something standardized in the industry, and it's always been like that since I've been in the industry, so it's something that probably won't change, and it's something that makes really life easy out there, and you don't have to have a scientific calculator to calculate you know 8.34 gallons and all the other things. If you really unpack the math, it gets really complicated and it's really interesting. But just note that the micron apart per million are a very small particle measurement that we use in the pool industry. Looking for other podcasts, you can find those by going to my website, swimming for learning.com, clicking on the the podcast icon on the banner. There'll be over 1800 podcasts there for you. And if you're interested in my coaching program, you can learn more at poolguidecoaching.com. Thanks for listening to this podcast. Have a great week and God bless.