Pool Chemistry Gone Wrong: Common Tech Mistakes Explained

Eyeballing pool chemicals feels fast, but it can quietly wreck your results and your margins. I walk through the most common pool water chemistry mistakes I see on pool routes, starting with the habit of default dosing: “a quart of acid,” “half a gallon of chlorine,” and other shortcuts that ignore what the water is actually doing. With today’s chemical prices, accuracy matters, and the good news is it does not have to mean slow, complicated math. A simple dosing app like poolcalculator.com can get you to the right number in about a minute.

From there, we get into why “balanced water” is bigger than clarity and sanitizer. The Langelier Saturation Index (LSI) helps you spot water that is corrosive (heater damage, staining risk, surface wear) or scale forming (tile line buildup, equipment scaling). I explain how tools like the Orenda app make LSI practical in the field and why ignoring it can turn routine acid additions into long-term damage.

We also talk about cyanuric acid (CYA) creep from trichlor tablets and how it snowballs through the season. As CYA rises, the free chlorine level required for effective sanitation rises too, which is why the 7.5% guideline matters. Finally, if you’re fighting algae, cloudy water, or chloramines, I explain why under-shocking often does almost nothing and how aiming beyond breakpoint chlorination can save you from repeat blooms next week.

Subscribe for more pool service and pool chemistry training, share this with a tech who still eyeballs doses, and leave a review with the chemistry mistake you want help fixing next.

We break down the pool water chemistry mistakes that waste chemicals, damage surfaces, and create repeat problems on a pool service route. I explain how quick dosing math, LSI awareness, and the right chlorine strategy make results more consistent and more profitable.  
• relying on rules of thumb instead of calculating doses  
• using dosing apps like poolcalculator.com to save time and money  
• understanding LSI to prevent corrosive water and scale forming water  
• recognizing cyanuric acid creep from trichlor tablets across the season  
• applying the 7.5% CYA to free chlorine guideline to keep chlorine effective  
• seeing how total alkalinity changes muriatic acid demand and pH drop risk  
• avoiding underdosing when shocking for algae, chloramines, and combined chlorine  
Learn more at swimmingpoollearning.com.  
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Transcript

Welcome And Episode Goal

SPEAKER_00 0:14

Hey, welcome to the Pool Guy Podcast Show. In this episode, I'm going to go over some common chemistry and chemical mistakes that you make out on your pool route. And these are things that maybe you don't think about too much and you're kind of doing automatically. And I'll go over some solutions and some practical reasons why this is probably not the best way to run your pool route. 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. This first one was very popular when I first started in the industry, and it's still popular today, I think, to some extent. That is kind of just eyeballing chemical readings. There are certain kind of rule of thumbs that have developed in the industry. You know, you do a pH test and it comes out at 7.8, and you just add a quart of acid to the pool, and you're not really checking any of the chemicals, you're just kind of going off of like the simple rule, like, oh, add a quart

Coaching Program Quick Invite

SPEAKER_00 1:26

of acid, and you'll be fine. So there are a lot of problems with just doing that. And eyeballing the chemical readings and kind of using rules of thumbs, like you know, half a gallon of liquid chlorine or a bag of cal hypo really is a little bit wasteful when it comes to chemicals nowadays. Now back before

Stop Eyeballing Chemical Doses

SPEAKER_00 1:45

COVID when when chlorine and everything was dirt cheap, eyeballing and then overdosing a pool was really not a big issue, but if you're really watching your bottom line and your pool service and you have employees out there putting chemicals in pools, it's really important to get a more exact calculation. Now you don't want to spend too much time overcalculating things and too much time doing math out there, but there it is pretty simple and it takes just about one minute to open up an app, and there are several dosing apps out there. I like the poolcalculator.com. It's one of my favorite dosing apps. You can purchase it one time on your phone, and then you can use that as your dosing guide. You know, the Taylor test kit does have a little booklet with some dosing in there as well. You can refer to that if you're old school and want to go that route. But I think apps are much better and easier. I'll give you a quick example of how fast you can calculate dosing a pool for muratic acid within like one minute. So I'm on the app now, I'm gonna go ahead and put in some numbers. The pool is gonna be 20,000 gallons of water, and the pH tested at 8, and I want to bring it down to 7.6 and let me see the alkalinity here. The alkalinity here is gonna be at 80, and I'm using 31.45% acid. It says to add 17 fluid ounces of the muriatic acid, which is about 2 cups and 0.92 fluid ounces, so a little over 2 cups of muriatic acid. That took about 45 seconds to do with the app. So it's not something that you're gonna spend a lot of time wasting out there doing that. And the next thing I'm gonna touch on is going to you're gonna understand more why just putting in a quart of acid and using rules of thumb or putting in half a gallon of liquid chlorine is not really cost effective and not really conductive to balancing the pool correctly. And this leads into the LSI or the Langlier saturation index. And this is basically an index that was developed for the industry that will allow you to understand or to tell if the pool water is corrosive, which is destroying the pool surface, or it's scale forming, which means scale is forming on the pool surface and tile lines and around the equipment area and you know into the equipment or plumbing. And so is the pool scale forming or is the water corrosive? No, if it's corrosive, it can damage the heater, cause metal staining. If it's scale forming, it can cause scale in the pool. And how do you determine this? Well, the best app for this is the Arenda app for sure. And just open the Arenda app, get it on your phone, and then it'll give you you can put the numbers in, water temperature,

LSI And Why It Matters

SPEAKER_00 4:30

other factors, and calculate the LSI. And that's why it's really important you that you don't just eyeball the pool or eyeball dosing, because depending on what the LSI is, you may not need to add, you know, the quart of acid or a quarter of a gallon of acid to the pool that may be too much acid and may make the water corrosive or maybe too less acid and have no effect on the water. So the LSI is a really important factor, and there's elements of the LSI that affect the corrosiveness or the scale forming of the pool water that you should be aware of. And so just ignoring the LSI entirely and just eyeballing dosing really does not lead to a very balanced water. And when I mean balanced, I don't mean that the water is clear and safe to swim in. That's part of balancing the water, but also part of balancing the water is making sure the pool is not corrosive or scale forming as well. Another common mistake that's made out there is kind of ignoring the fact that cyaneric acid will creep up in the pools over time over the season, especially if you're using trichlor tablets. And this creep is pretty gradual, and it starts off when you start using them in May, and it kind of peaks in August and September when you're ending the season. How much cyaneric acid would you add to the pool? It really depends on how many tablets you're using in that pool. Let's just say that you have a 20-pound bucket of trichlor tablets you're going to use in the season, and you're going to use that whole bucket from May all the way to August, September. How much cyaneric acid did you add to that pool? Well, you've added about 10 pounds of cyaneric acid because the tablets are about 50% cyaneric acid. So I have my trusty calculate pool

Trichlor Tablets And CYA Creep

SPEAKER_00 6:14

calculator over here. Let's say we're dealing with a 14,000 gallon pool. And let's say you started a season at 50 parts per million of cyaneric acid, and you added 20 pounds of trichlor tablets during the season. By August, your trichloride level, your actually your cyaneric acid level, I should say, is 140 parts per million. That's 10 pounds. So I put in the calculator starting at 50 parts per million. My goal is 140, and that means I have to add 172 fluid ounces of stabilizer, which is a little bit over 10 pounds of cyaneric acid. So at the end of the season, that pool's at 140. And if you're not you're not getting a lot of rain and dilution over the course of the winter, that may stay pretty elevated as the next season starts. And you can easily get the 200 parts per million into the second season using trichloritablets without a partial drain or without a lot of rain to dilute that pool water. And the problem is not that you just raise the cyaneric acid by about three times what you started with at the season. It's the 7.5% formula that I talk about all the time here that Bob Lowry came up with. And let's say at the beginning of the season you're at 50 parts per million. So that means that you're going to take that 50 parts per million and take 7.5%. So 50 times 7.5%. And that's going to be 3.75, which is about 4 parts per million. So at the beginning of the season in May, it'll take 4 parts per million of free chlorine in the pool to keep the water looking good and stable. By the time you get to August, you're going to be close to 140 parts per million of cyaneric acid. So 140 times 7.5%. That means you're going to need to keep that chlorine level at about 11 parts per million for the chlorine to be effective in the pool. And that's why it's kind of one of those kind of a snowballing effect when you're using trichloride tablets, because you have to add more and more as the season goes on to increase the free chlorine level. And this, of course, increases the cyanaric acid level at the same time. And that's why you're going to have to do a partial drain or maybe use a combination of trichlor tablets and liquid chlorine in the pool so that the cyaneric acid doesn't get out of hand. Because by the near the end of the season, you're going to need to keep again that free chlorine level at about 11 parts per million because the cyaneric acid went from 50 to about 140 in the course of that those few months while you're using the trichlor tablets as your primary sanitizer. Again, this can be mitigated by using less tablets and by using liquid chlorine to raise the chlorine level and maybe put one or two less tablets in the pool every week. I'll go ahead and use the calculator again to give you a good example here. And you get an idea of eyeballing it or just putting in a quart of acid may not solve the problem. Let's just say the alkalinity is at 160 parts per million, which is not unheard of out there in the industry to have higher alkalinity in some pools. Go back to 20,000 gallons here, and let's say the alkalinity is at 160. How much acid? 31.45% acid do I need to add to the pool to bring it down from eight pH of a pH of an eight to a 7.6. I'm going to need to add 31 fluid ounces, which is three cups of muranic three three and a half cups of muratic acid to that pool. If the alkalinity is 160 to drop it from 8

Alkalinity Changes Acid Demand

SPEAKER_00 10:18

to 7.6. But if that alkalinity is at 70 in that pool, how much muralic acid do I need to add to that pool? I just need to add one cup and seven ounces. About half the amount of muratic acid if the alkalinity is at 70 in that pool. And you can see that the water can get extremely corrosive very rapidly. If you were to add the three cups of acid to the pool, or a quart of acid to the pool, let's say, without testing the water and testing the alkalinity, you actually will drop the pH from 8 to 7 in that pool if you're adding 3 cups of marinic acid to that pool with the alkalinity at 70. And so you're not going to hit 7.6, you're actually going to hit 7.0 in there, which is falling close to the corrosive level of acid in the pool. So eyeballing it and not knowing the alkalinity is a very dangerous thing to do. And of course, you're not accounting for the LSI either if you're adding the acid without checking the alkalinity, and you're just adding a quart of acid at every pool without really calculating how the alkalinity affects that. You may be adding too less acid to the pool if the alkalinity is high in that pool, or too much acid to that pool if the alkalinity is really low in that pool. And this is something that you really need to teach your employees as well. You just can't eyeball it and add a quart of acid to every account. And by the way, a quart of acid is actually about four cups. And so all my calculations and everything I've been doing here have actually been less than a quart of acid. So you can really overdose the pool very quickly, and it's something to be aware of out there on your pool route that you really can't eyeball muratic acid effectively. Here's another one that's pretty common now. And again, at the beginning I talked about just kind of overdosing the pool without calculating. I would just go crazy and add a ton of chlorine to the pool and not really worry about it because it was dirt cheap. You know, Calhypa was like $1.50 a pound. It was just insanely inexpensive to add chlorine to the pool. And so you flip that now to where chlorine is really expensive. And I think a lot of people are a little bit overconscious when it comes to shocking the pool and bringing the chlorine level up to a high level if there's algae or combined chlorine or chloramines in the pool. And what can happen is you actually add too little now to the pool. I know it's not a contradiction

Shocking Pools Without Underdosing

SPEAKER_00 12:53

what I'm saying here, it's just that now that you're more careful and you're kind of watching how much chlorine to add to the pool, you're getting a little more exact with your science and with the dosage. But that can actually hurt you because when it comes to algae and chloramines and combined chlorine, more is still better. And I always would suggest going over the breakpoint chlorination and over what you would think would be a regular dose. Because when you add too little to the pool with algae and you're shocking the pool to bring the chlorine level up, or if the pool has chloramines, it really has a nil effect on the pool. What I mean by that is if you see like mustard algae in the in the corners of the pool and then you treat it, and maybe you'll put a copper algacyte or a polyquat 60 in there. And the problem is when you just put maybe a gallon of liquid chlorine and bring it up from zero to five parts a million, that's not enough to combat the algae in the pool. And basically in a couple days it'll be at zero again. And when you get back there later the next week, when you get back there, the pool is gonna have even more algae, and that's why it's okay to calculate exactly. And I'm not saying that an exact calculation wouldn't work in a lot of cases, but I always would caution you that sometimes the exact calculation is not enough chlorine, if that makes sense. You also have the cyaneric acid to free chlorine ratio that I talked about to 7.5%. And if the cyaneric acid is at 100 parts per million in the pool, you're going to need eight parts per million of free chlorine in that pool to be effective. And so if the pool is at zero and you bring it up to five parts per million, and you need to be at eight parts per million for the chlorine to be effective, you're not going to really treat that algae or treat the cloudy water effectively or the chloramines. You would want to bring that chlorine up to, of course, eight parts per million, which is the baseline, and then maybe double that to 16 or 20 parts per million to kind of break any combined chlorine and help destroy the algae in the pool or kill the algae in the pool. And you just have to understand that it's one of those things where every pool is a little different and every situation is a little bit different if depending on how much algae is in the pool or how cloudy the pool is or how many how much chloramines are in the pool will require more shock. So, in reality, the shock level of 10 parts per million wouldn't do too much in a pool where the free chlorine needs to be at 8 parts per million. If the cyaneric acid is at 100 and you have to keep it at 8 parts per million for the pool for the chlorine to be effective, bringing it to 10 parts per million is not going to do much to that pool. Bringing it to 20 parts a million will definitely break the combined chlorine in a lot of cases, or if the pool's cloudy or if you have algae, bringing it to 30 parts per million would be much more effective. With if your baseline is eight parts per million, if that makes sense. If your baseline is five parts per million, bringing it to 15 or 20 parts a million would have a better effect in the pool than bringing it to just 10 parts per million. So as far as shocking the pool, treating algae, cloudy water, and chloramines, I always would say err on the side of adding more chlorine to the pool than less chlorine in the pool, and you're going to have a better experience out there the following week when you get back there. When you added more chlorine to the pool, even though it's going to cost more, it'll cost even more if you don't add the right amount of chlorine and you're treating the pool for even bigger algae bloom the following week. If you're looking for other podcasts, you can find those by going to my website, swimming4learning.com, on the podcast, on the banner there's a podcast icon. Click on that, and there'll be over 1900 podcasts for you to listen to there. And if you're interested in the coaching program, you can learn more at poolguycoaching.com. Thanks for listening to this podcast. Have the rest of your week. God bless.