Show Notes
“Trichlor is 90% available chlorine, so it must be the strongest” sounds logical until you follow the math all the way through. We sit down with Bob Lowry to untangle the biggest chlorine strength myth in pool care, breaking down what “available chlorine” actually means, why the industry compares everything to chlorine gas, and how a percentage on a bucket can mislead even experienced pool owners and pool service pros.
We talk through the practical way to think about dosing: pounds of chlorine delivered to the water. That’s where liquid chlorine (sodium hypochlorite) often surprises people, because a gallon of 12.5% can deliver about a pound of available chlorine even though the label number looks “small.” We also unpack why trichlor’s label ends up doubled when compared to the chlorine gas standard, and how competing terms like weight percent, trade percent, and liquid concentration keep the marketplace confusing.
From there, we zoom out to the real-world tradeoffs that matter more than bragging rights: every chlorine type adds something to the pool. Liquid chlorine adds salt over time, cal hypo adds calcium, and stabilized chlorines like dichlor and trichlor add cyanuric acid. We also get blunt about saltwater chlorine generators: they do make chlorine, along with sodium hydroxide and hydrogen gas, which ties directly to rising pH, corrosion risk when water evaporates and leaves salt behind, and the need for proper bonding to avoid electrolysis problems. If you’ve ever relied on “boost” mode to shock, we explain why that’s not the same as rapid superchlorination.
Subscribe for more pool water chemistry clarity, share this with a pool owner who argues about tablet vs liquid, and leave a review with the chlorine question you want us to tackle next.
We clear up the myth that a higher percentage on the label automatically means a stronger pool sanitizer. We walk through how “available chlorine” is calculated, why chlorine gas is the comparison standard, and what salt systems really produce in your water.
• why liquid chlorine can deliver about a pound of chlorine per gallon
• how trichlor’s “available chlorine” number is based on a comparison standard
• weight percent vs trade percent and why labels confuse buyers
• what chlorine gas actually does in water and why the standard persists
• the hidden add-ons from each chlorine type: salt, calcium, cyanuric acid
• why saltwater generators are chlorine generators and what else they create
• output limits, voltage/current issues, and salt level problems that reduce chlorine production
• corrosion, evaporation salt residue, and why proper bonding matters
• why SWGs raise pH and why boost mode is not a true shock
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Show Transcript
Welcome And The Chlorine Myth
SPEAKER_00 1:04
Hi, welcome to the Pool Guy Podcast Show. At this best of Bob Lowry episode, I want to talk to Bob Lowry about which chlorine type is stronger. There's a lot of myths out there about which chlorine type is stronger, and you may think that trichlor is the strongest because it's 99% available chlorine. But does that mean that it's the strongest chlorine out there? And Bob Lowry unpacks this for you here available chlorine. Chlorine by weight, and you may be surprised of what the strongest chlorine type actually is. 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
Available Chlorine Vs Real Strength
SPEAKER_00 1:55
more at Swimming Poollearning.com. So I get this all the time. So someone says, you know, liquid chlorine is really weak because it's only 12.5% compared to the trichlor tablets, which are 99% available chlorine. What is the available chlorine percentage? How do you get it from one from a dry chemical to a liquid chemical or from trichlor to cal hypo? How is that calculated or compared? Because it's really confusing out there in the market. I've even seen manufacturers use their chlorine percentage to kind of beat down the competition.
SPEAKER_01 2:29
Yeah, there's a a confusing array of terms used when you describe how much chlorine is in a product. What people are used to is what we call a weight to weight percent. So if you put in a pound of something into 10 pounds of something, it's it's 10%. And so that's the way we are used to hearing things. But then there are what we call trade percent, which is a made-up term, and then there is actually a a volume to volume term, which is not weight to weight. That's a you know a quart of something and ten quarts of something, and it's not weight to weight. So there's different ways of of describing it. But the the practical thing is this the amount of chlorine in a gallon of liquid chlorine is about one pound of pure chlorine. And in a pound of trichlor, it is about ninety percent of one pound. So you can either think of it as ninety percent of a pound, or it would take 1.15 pounds to equal one pound, either way. So you can tell from that if
Why Chlorine Gas Sets The Standard
SPEAKER_01 4:00
something says it's it's 55% available chlorine on it, then that's compared to what one pound of chlorine is. Furthering the confusion is that years ago when they tried to make a a method of comparing chemicals, they said chlorine or pure chlorine, gas chlorine, when you put it in water, makes a hundred percent. There's nothing in it, so it's a hundred percent, right? Well, yes, but what happens is when you put pure chlorine in the pool, it is chlorine gas, and the formula for chlorine gas is Cl2, which means it's two atoms of chlorine. So when you put it in water, one atom makes HOCL, and the other atom makes HCl acid. So technically, only 50% of that molecule of chlorine is making chlorine in the pool. The other one's making acid, but they assigned it a value of 100%. So now how do you compare, you know, against chlorine gas, how do you compare it? That's the way it came about, and that's that's we use chlorine gas as a standard, but chlorine gas is technically only 50% of it is making making chlorine in the water.
SPEAKER_00 5:41
So is it safe to say that liquid chlorine compared to cal hypodichlor, trichlor, has a larger available percentage, even though it's a liquid, just based on the math that you were saying? Yes.
SPEAKER_01 6:18
And if you had a product that was 50% available, you'd need two pounds of it to equal one pound of gas chlorine. Yeah, it makes perfect sense. So the only and that's of dry products. When you get to liquids, it's it changes because liquid is a a a weight a weight percent. So generally we just say there's a pound of chlorine in a gallon. A pound of pure chlorine in a gallon. Or 12.5 uh liquid chlorine. If it's 12.5 percent, if it's 10 percent, it's it doesn't have a pound. It's like you know, nine-tenths
What Each Chlorine Adds To Water
SPEAKER_01 7:01
of a pound.
SPEAKER_00 7:01
Yeah, that's important for people to know the strength of the chlorine. So sometimes they're they can be fooled thinking that certain chlorines are more powerful just based on what you just said. And it is confusing. So after you even after you explained it, it's still really confusing.
SPEAKER_01 7:16
Well, so uh a little bit further into what we're doing, technically trichlorine, if you actually calculated the molecules in it, technically trichlor is about 45% chlorine. Because we have to compare it to gas chlorine, we literally have to double it. And that's why the package says it's 90% available chlorine instead of saying that it's 45%.
SPEAKER_00 8:05
Basically, you know, for the average person out there, the chlorine that is attached to some product, and you're gonna have a byproduct. You know, liquid chlorine
How Salt Systems Make Chlorine
SPEAKER_00 8:15
has salt, calhypo has the calcium, dichlor and trichlor have the cyaneric acid, is that correct? Right.
SPEAKER_01 8:23
So everything is gonna add something to the water that you may or may not have to deal with. Either cyanuric acid, sodium, calcium, something that you're gonna have to to build up or deal with. Yes.
SPEAKER_00 8:43
And let's touch on the salt water generators because they're pretty popular and manufacturers are pushing them with the current trichlor shortage. People think, of course, they're not a chlorine-producing device, but they are.
SPEAKER_01 8:57
Chlorine generators, they actually make chlorine gas. But because it's being made in water, the chlorine gas dissolves right away and makes hypochlorous acid. So it technically makes chlorine gas. It also makes sodium hydroxide, it makes hydrogen gas. And so it makes those three things from salt that you add to the pool. And I often hear this we have a salt pool, we don't use chlorine, and that couldn't be any farther from the truth. The fact of the matter is, if you have a salt pool, you're making chlorine. Most of the chlorine generators are capable of making about one pound of pure chlorine per day, if they ran 24 hours a day at 100%. One of the things I've recently found out is that the the controllers and all the electronics that are out there, sometimes the chlorine generators are not getting the correct current, the correct voltage. And when it doesn't get the correct voltage, then it doesn't make that pound of chlorine. So the the voltage, the DC current that it needs is critical. There is a specification for the cells and how much current they need. And you can also then check it with a meter to see if it's getting the right amount of current. And we had a guy that had a 26,000 gallon pool and he was having to run his chlorinator 100% 24 hours a day, and he was barely keeping up with it. And it wasn't because he was using so much chlorine, it should have been making four parts per million of chlorine per day in that pool. And it wasn't, it's important that you get the right current to the unit. But aside from that, you need the right salt level. If you get too much salt or too little salt, then there's a problem. Also understand that people say, well, you know, this salt water's not good for you, or salt water is good for you, or
Output Problems Voltage And Salt Level
SPEAKER_01 11:11
it's only a little bit of salt, and so on. And the answer is, yeah, it's only a little bit of salt, but the fact of the matter is that it's only one-tenth of what's in the ocean. And the amount of salt that's in the pool is actually very close to the amount of salt that's in your tears. So swimming in it is not like swimming in the ocean. But people need to understand is that when the water goes out of the pool and sits on the deck or handrail or anywhere around the pool, as long as it's still a liquid, no problem. But when the water evaporates away, it leaves the salt behind. And now you have a hundred percent salt on whatever that water was on. Whether it's aluminum, you know, some of your travertine deck or whatever, it's like you took some Morton salt and poured on it. It's corrosive. Bonding becomes an issue. And what I mean about bonding is that you should have a common copper wire that connects each piece of electrical equipment to a ground and not just the pipe that runs in the ground. Better to have it on a stake or a rod that goes that's driven into the ground. If you don't do that, because you put salt in the water, it conducts electricity better. And so you can have problems with electrolysis and and and and other problems in the pool because it's not bonded correctly. So it needs to be bonded, and you need to make sure that the pool has done that. Because with electricity and the pool and so on, your pool is actually a giant low voltage battery. And if you don't ground it, you know, guess what happens? You know,
Corrosion Risk And Proper Bonding
SPEAKER_01 13:11
it's the same thing as leaving the batteries in your flashlight for three years and then opening it up. What do you think it looks like? So it's important to know that. Also understand that the chlorine generator, the pH of your pool is going to go up. And it's going to go up for a couple of reasons. One is it makes hydrogen hydrogen, uh, I'm sorry, sodium hydroxide. And so because it makes sodium hydroxide, the pH goes up because of the hydroxide. It also makes hydrogen gas. And hydrogen gas is a bubble. It's it's an aeration. And and because there's a number of plates in the cell, there's turbulence. So you have turbulence and aeration, and the turbulence and aeration is continuous, and it raises the pH of the pool due to CO2 off-gassing. These are some of the things that you need to be aware of. They you you cannot shock a pool with a chlorine generator. If you need to superchlorinate your pool, hitting the boost button, you know, raises the chlorine level up about double over a 24-hour period. That's not shocking the pool. What you need to do, if you need to shock your pool, is take some liquid chlorine or cal hypo and put it in the pool and get the chlorine level up
pH Rise And Why Boost Is Not Shock
SPEAKER_01 14:37
very fast right now.
SPEAKER_00 14:38
Yeah, we should clarify that that boost mode on the salt generator, all it does is increases it 100% output. Doesn't do it, it doesn't add any more chlorine to the pool per se. It just increases the output of the system. If you're looking for more podcasts, you can find those by going to my website, swingpoollearning.com. On the banner, click on the podcast icon. That'll take you to a drop down menu where I have over two thousand podcasts. And if you're interested in the coaching program that I offer, you can learn more at poolguidecoaching.com. Thanks for listening to this podcast. Have a rest of your week and God bless.
Listen On
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Starting a pool service business can change your life, but only if you go in wit -
Pool Service Bloopers That Can Hurt You
A pool filter mistake can go from “oops” to life-threatening in seconds, and tha -
The Reality of Running a Pool Service Business
A customer points at a stain on the deck and says your chemicals did it. Another -
Pool Service Business Mistakes That Hold You Back
If you’re trying to grow a pool service business on your own, the hardest part u
Chapters
- 0:00 Welcome And The Chlorine Myth
- 1:55 Available Chlorine Vs Real Strength
- 4:00 Why Chlorine Gas Sets The Standard
- 7:00 What Each Chlorine Adds To Water
- 8:15 How Salt Systems Make Chlorine
- 11:11 Output Problems Voltage And Salt Level
- 13:11 Corrosion Risk And Proper Bonding
- 14:36 pH Rise And Why Boost Is Not Shock
- 16:11 Where To Get More Help
Transcript
Welcome And The Chlorine Myth SPEAKER_00 1:04 Hi, welcome to the Pool Guy Podcast Show. At this best of Bob Lowry episode, I want to talk to Bob Lowry about which chlorine type is stronger. There's a lot of myths out there about which chlorine type is stronger, and you may think that trichlor is the strongest because it's 99% available chlorine. But does that mean that it's the strongest chlorine out there?
And Bob Lowry unpacks this for you here available chlorine. Chlorine by weight, and you may be surprised of what the strongest chlorine type actually is. 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 Available Chlorine Vs Real Strength SPEAKER_00 1:55 more at Swimming Poollearning.com.
So I get this all the time. So someone says, you know, liquid chlorine is really weak because it's only 12.5% compared to the trichlor tablets, which are 99% available chlorine. What is the available chlorine percentage? How do you get it from one from a dry chemical to a liquid chemical or from trichlor to cal hypo?
How is that calculated or compared? Because it's really confusing out there in the market. I've even seen manufacturers use their chlorine percentage to kind of beat down the competition. SPEAKER_01 2:29 Yeah, there's a a confusing array of terms used when you describe how much chlorine is in a product.
What people are used to is what we call a weight to weight percent. So if you put in a pound of something into 10 pounds of something, it's it's 10%. And so that's the way we are used to hearing things. But then there are what we call trade percent, which is a made-up term, and then there is actually a a volume to volume term, which is not weight to weight.
That's a you know a quart of something and ten quarts of something, and it's not weight to weight. So there's different ways of of describing it. But the the practical thing is this the amount of chlorine in a gallon of liquid chlorine is about one pound of pure chlorine. And in a pound of trichlor, it is about ninety percent of one pound.
So you can either think of it as ninety percent of a pound, or it would take 1.15 pounds to equal one pound, either way. So you can tell from that if Why Chlorine Gas Sets The Standard SPEAKER_01 4:00 something says it's it's 55% available chlorine on it, then that's compared to what one pound of chlorine is. Furthering the confusion is that years ago when they tried to make a a method of comparing chemicals, they said chlorine or pure chlorine, gas chlorine, when you put it in water, makes a hundred percent. There's nothing in it, so it's a hundred percent, right?
Well, yes, but what happens is when you put pure chlorine in the pool, it is chlorine gas, and the formula for chlorine gas is Cl2, which means it's two atoms of chlorine. So when you put it in water, one atom makes HOCL, and the other atom makes HCl acid. So technically, only 50% of that molecule of chlorine is making chlorine in the pool. The other one's making acid, but they assigned it a value of 100%.
So now how do you compare, you know, against chlorine gas, how do you compare it? That's the way it came about, and that's that's we use chlorine gas as a standard, but chlorine gas is technically only 50% of it is making making chlorine in the water. SPEAKER_00 5:41 So is it safe to say that liquid chlorine compared to cal hypodichlor, trichlor, has a larger available percentage, even though it's a liquid, just based on the math that you were saying? Yes.
SPEAKER_01 6:18 And if you had a product that was 50% available, you'd need two pounds of it to equal one pound of gas chlorine. Yeah, it makes perfect sense. So the only and that's of dry products. When you get to liquids, it's it changes because liquid is a a a weight a weight percent.
So generally we just say there's a pound of chlorine in a gallon. A pound of pure chlorine in a gallon. Or 12.5 uh liquid chlorine. If it's 12.5 percent, if it's 10 percent, it's it doesn't have a pound.
It's like you know, nine-tenths What Each Chlorine Adds To Water SPEAKER_01 7:01 of a pound. SPEAKER_00 7:01 Yeah, that's important for people to know the strength of the chlorine. So sometimes they're they can be fooled thinking that certain chlorines are more powerful just based on what you just said. And it is confusing.
So after you even after you explained it, it's still really confusing. SPEAKER_01 7:16 Well, so uh a little bit further into what we're doing, technically trichlorine, if you actually calculated the molecules in it, technically trichlor is about 45% chlorine. Because we have to compare it to gas chlorine, we literally have to double it. And that's why the package says it's 90% available chlorine instead of saying that it's 45%.
SPEAKER_00 8:05 Basically, you know, for the average person out there, the chlorine that is attached to some product, and you're gonna have a byproduct. You know, liquid chlorine How Salt Systems Make Chlorine SPEAKER_00 8:15 has salt, calhypo has the calcium, dichlor and trichlor have the cyaneric acid, is that correct? Right. SPEAKER_01 8:23 So everything is gonna add something to the water that you may or may not have to deal with.
Either cyanuric acid, sodium, calcium, something that you're gonna have to to build up or deal with. Yes. SPEAKER_00 8:43 And let's touch on the salt water generators because they're pretty popular and manufacturers are pushing them with the current trichlor shortage. People think, of course, they're not a chlorine-producing device, but they are.
SPEAKER_01 8:57 Chlorine generators, they actually make chlorine gas. But because it's being made in water, the chlorine gas dissolves right away and makes hypochlorous acid. So it technically makes chlorine gas. It also makes sodium hydroxide, it makes hydrogen gas.
And so it makes those three things from salt that you add to the pool. And I often hear this we have a salt pool, we don't use chlorine, and that couldn't be any farther from the truth. The fact of the matter is, if you have a salt pool, you're making chlorine. Most of the chlorine generators are capable of making about one pound of pure chlorine per day, if they ran 24 hours a day at 100%.
One of the things I've recently found out is that the the controllers and all the electronics that are out there, sometimes the chlorine generators are not getting the correct current, the correct voltage. And when it doesn't get the correct voltage, then it doesn't make that pound of chlorine. So the the voltage, the DC current that it needs is critical. There is a specification for the cells and how much current they need.
And you can also then check it with a meter to see if it's getting the right amount of current. And we had a guy that had a 26,000 gallon pool and he was having to run his chlorinator 100% 24 hours a day, and he was barely keeping up with it. And it wasn't because he was using so much chlorine, it should have been making four parts per million of chlorine per day in that pool. And it wasn't, it's important that you get the right current to the unit.
But aside from that, you need the right salt level. If you get too much salt or too little salt, then there's a problem. Also understand that people say, well, you know, this salt water's not good for you, or salt water is good for you, or Output Problems Voltage And Salt Level SPEAKER_01 11:11 it's only a little bit of salt, and so on. And the answer is, yeah, it's only a little bit of salt, but the fact of the matter is that it's only one-tenth of what's in the ocean.
And the amount of salt that's in the pool is actually very close to the amount of salt that's in your tears. So swimming in it is not like swimming in the ocean. But people need to understand is that when the water goes out of the pool and sits on the deck or handrail or anywhere around the pool, as long as it's still a liquid, no problem. But when the water evaporates away, it leaves the salt behind.
And now you have a hundred percent salt on whatever that water was on. Whether it's aluminum, you know, some of your travertine deck or whatever, it's like you took some Morton salt and poured on it. It's corrosive. Bonding becomes an issue.
And what I mean about bonding is that you should have a common copper wire that connects each piece of electrical equipment to a ground and not just the pipe that runs in the ground. Better to have it on a stake or a rod that goes that's driven into the ground. If you don't do that, because you put salt in the water, it conducts electricity better. And so you can have problems with electrolysis and and and and other problems in the pool because it's not bonded correctly.
So it needs to be bonded, and you need to make sure that the pool has done that. Because with electricity and the pool and so on, your pool is actually a giant low voltage battery. And if you don't ground it, you know, guess what happens? You know, Corrosion Risk And Proper Bonding SPEAKER_01 13:11 it's the same thing as leaving the batteries in your flashlight for three years and then opening it up.
What do you think it looks like? So it's important to know that. Also understand that the chlorine generator, the pH of your pool is going to go up. And it's going to go up for a couple of reasons.
One is it makes hydrogen hydrogen, uh, I'm sorry, sodium hydroxide. And so because it makes sodium hydroxide, the pH goes up because of the hydroxide. It also makes hydrogen gas. And hydrogen gas is a bubble.
It's it's an aeration. And and because there's a number of plates in the cell, there's turbulence. So you have turbulence and aeration, and the turbulence and aeration is continuous, and it raises the pH of the pool due to CO2 off-gassing. These are some of the things that you need to be aware of.
They you you cannot shock a pool with a chlorine generator. If you need to superchlorinate your pool, hitting the boost button, you know, raises the chlorine level up about double over a 24-hour period. That's not shocking the pool. What you need to do, if you need to shock your pool, is take some liquid chlorine or cal hypo and put it in the pool and get the chlorine level up pH Rise And Why Boost Is Not Shock SPEAKER_01 14:37 very fast right now.
SPEAKER_00 14:38 Yeah, we should clarify that that boost mode on the salt generator, all it does is increases it 100% output. Doesn't do it, it doesn't add any more chlorine to the pool per se. It just increases the output of the system. If you're looking for more podcasts, you can find those by going to my website, swingpoollearning.com.
On the banner, click on the podcast icon. That'll take you to a drop down menu where I have over two thousand podcasts. And if you're interested in the coaching program that I offer, you can learn more at poolguidecoaching.com. Thanks for listening to this podcast.
Have a rest of your week and God bless.