15 Alkalinity reading false

This is Janine with Pool Zones, and just when you thought you had learned everything you needed to know about pool chemistry, there is one more very important aspect about alkalinity and cyanuric acid also known as conditioner.

So, let’s take a look at that. Now, there is an adjustment to make and what I’m talking about here is so far what you’ve been doing is when you test alkalinity, you have been writing down what is called total alkalinity.

And that number has been a maybe 140, maybe 180, maybe 100, whatever it is. You have been writing that down believing that that is the number that is the alkalinity. Well it was up until you add cyanuric acid, and once you added that cyanuric milky looking acid, then that gives you what we call an inaccurate reading, a false reading, let me explain to you what needs to be done to adjust the alkalinity, adjust the reading. 

  • So you take the alkalinity reading say 100
  • You put the number aside, you write it down; a hundred – 100
  • Take the cyanuric reading say it is 60 for example… yeah okay it is a little bit higher than we anticipated but we have 60.
  • Divide this number – the cyanuric by 3, you get 20, simple math
  • Subtract the 20 from the alkalinity number
  • The answer is the adjusted alkalinity;


Total alkalinity 100
Cyanuric is 60
Total alkalinity 100 minus the 1/3, the 20 = 80 adjusted alkalinity.

That is the correct reading, the adjusted alkalinity, so be careful, after you’ve added cyanuric acid, wait a few days, three or four days and then when you test, you need to make a subtraction. Then it will just end on the cyanuric acid reading. 

Now here’s another situation. Let’s make things a little more complicated, because that’s too easy. 

Say for example, you did come up with 80 in the alkalinity reading, but whoops, that afternoon it rained heavily for five days, When you tested it again, that alkalinity dropped down to something like 40, 30, 20… you have a really serious condition in that pool. 

And once that alkalinity starts plummeting remember because we have one – in Houston, Texas- we have acid rain, and once it drops down into those ranges, and you finally get around to it, if you’re lazy, because it’s raining out there you’ll wait, and the following week you go to leslies and they say;  you’ve got to get that up in here, and you go rushing out with that 20 pound bag or whatever it is and you mix it up and throw it all in the pool.

And then suddenly you look at the pool a day or two later and you wonder, what the hell is that white stuff on the surface that will not brush off and I’m going to tell you that that is… has happened, it’s exactly what happens, and it is the fastest way to destroy a perfectly good interior.

And then the homeowner gets on the phone call support and says, there is  something wrong with the interior, you better come and fix it. And the first thing he does is he takes samples and he looks at it so no, that’s actually calcium and that’s precipitated out and you have scale. And there’s really nothing we can do about your interior. 

And I can’t tell you how often that happens, but it does happen, and it happens frequently. And one of the reasons for these videos is so that your interior will look beautiful from the beginning and for decades. 

As long as you have pebble and as long as you are maintaining that interior using these extremely simple principles, and what you gain from this course is an understanding of what you’re doing. 

Now one more caveat for you. When you go to the Leslie’s or when you talk to pool service guys, everyone will have an opinion, don’t go buy their opinions, don’t go buy what the guy says and then this guy says something different and this one says something different. 

Each one will have a different experience. You must stick to the principles, if you know the sequence, if you know to add small quantities. If you know about the principle of for example, the alkalinity/cyanuric and how they affect each other, then you won’t fall into the trap of going by what some guy tells you at a pool store, or what a service guy might tell you from his experience, you will know, based on your understanding of the principles.