In Pool School 103 I talked about pH and how people get confused with the terminology when we refer to the pH being either Acidic or Alkaline, so Pool School 104 is where we are going to clear up that confusion and explain why this mineral level in the pool is important.
When we are talking about Alkalinity we are really talking about Total Alkalinity, which is a measure of all the alkaline minerals, dissolved into the pool water. Remember when the pH is above 7.0 the pH is considered alkaline, but here we are talking about alkaline minerals dissolved into the pool water not pH (the amount of hydrogen in the water).
The question often posed to us is; Why is Total Alkalinity important? There are actually two mineral balances that are important to your pool water and water in general; they are Total Alkalinity and Total Calcium Hardness. In this class I am just going to talk about Total Alkalinity and I will address Total Calcium Hardness in Pool School 105.
You will want to remember this for this class and for the next class; water wants a certain water balance, if it does not have that balance then it will go looking for it in whatever vessel it is being contained in. So in our case it is the surface of the pool that will be in jeopardy if the water is “out of balance.” Vinyl and painted surfaces will be the most often affected if your Total Alkalinity is not properly maintained.
What is the correct level for your pool? There isn’t actually one level that you would maintain but a range, we like 100 ppm to 150 ppm. This range gives you a good buffer. Some sanitizing systems require a different range usually 80 ppm to 100 ppm. People who use Ionizers (we talked about in Pool School 102) would maintain this level in the pool. There are some areas of Hampton Roads where getting the Total Alkalinity down below 150 is almost impossible because their make up water is very high in Total Alkalinity, for these customers we usually will allow up to 200 ppm but we have to balance that with the Total Calcium Hardness so we don’t end up with other problems in the pool.
What happens if the Total Alkalinity is below 100 ppm? The lower the Total Alkalinity the more difficult it will be to maintain a steady pH level. Total Alkalinity actually acts as a buffer to the pH, like a shock absorber so you don’t get big swings of the pH when you are trying to adjust it. In addition, you can actually get the Total Alkalinity down to zero (0) where there are no alkaline minerals in the water. This is a condition you really don’t want because the water is going to begin removing minerals from the surface of the pool and in a vinyl liner pool you will begin to see wrinkles form as the liner begins to relax and stretch. The wrinkles can only be removed by replacing the liner.
What happens if the Total Alkalinity is above 200 ppm? When the Total Alkalinity is too high it will have the opposite effect on the pH from a too low situation. So it creates a pH lock where you cannot get the pH level to move no matter how much pH lower or pH rise you add. It may also, if the pH gets too high, create an environment where scale is likely to form anywhere and everywhere on the pool surface, plumbing and equipment. When scale forms it is very difficult to remove from the pool surface, note I said difficult I did not say impossible. It takes weeks for the chemicals that remove scale from the pool surface to do their job, so prevention is your best protection.
Total Alkalinity is not a balance that changes day to day like Chlorine and pH, Total Alkalinity is a more long-range balance. What causes Total Alkalinity to change? Total Alkalinity has to be affected in order for it to change. The most common thing to affect Total Alkalinity is rain; rainwater is distilled water that has no minerals. So if you get a lot of rain your Total Alkalinity will be decreased the more rain the more the Total Alkalinity will be affected. If we get a hurricane with 20” of rainwater you can pretty much plan on having to adjust your Total Alkalinity. The other thing that affects Total Alkalinity is stabilized chlorine tablets and muriatic acid. Stabilized chlorine tablets have a pH level of about 2, so when they are dissolved into the pool water they drag down the pH level and the Total Alkalinity. At least once a week it is important that you check not only the chlorine level in your pool but also the pH level. You will usually find that the pH level will have dropped and will have to be adjusted up to keep the pH from falling below 7.0. If you let the pH level drop below 7.0 the water has gone from alkaline to acidic, once the water is on the acidic side it will begin to dissolve all the alkaline minerals from the pool water slowly dragging down the Total Alkalinity. If you let this go on for weeks on end you will end up with zero (0) Total Alkalinity, a very bad place to be. The other thing that affects Total Alkalinity is muriatic acid, we use muriatic acid to lower the Total Alkalinity when the level is 200 ppm or higher. There is a specific process we use to lower Total Alkalinity when using muriatic acid. When you have the water tested here and we determine that it needs to be decreased we will give you specific instructions on how this is to be done.
Some important things to remember; the Total Alkalinity does not change everyday and really only needs to be checked and adjusted every two to three months. If you are using stabilized chorine tablets keeping the pH above 7.0 is very important and should be checked and adjusted weekly. If you are busy and really don’t have time to keep close track of the pH we have a product that will help keep the pH in check called Balancer Tabs. When you add your chlorine tablets to your chlorine feeder you put one Balancer Tablet in the skimmer for every chlorine tablet you put in your chlorine feeder. NEVER put the Balancer Tablets in the chlorine feeder or the chlorine tablets in the skimmer with Balancer Tablets. Using Balancer Tablets will make it less likely the pH and Total Alkalinity will go way out of whack, but they do not eliminate the need to test the pool water at home or at our test lab, they just help keep the water balance from going too far out of whack.
Now that you have a better understanding of Total Alkalinity in Pool School 105 we will be talking about Total Calcium Hardness and your pool water, don’t be late for class!
The Guru of Pools at