Cyanuric Acid

What a confusing chemical we have here. The confusion begins with the fact that there are no less than three names that it goes by. Stabilizer, conditioner, and cyanuric acid (CYA) all describe the same chemical. To make it a little more confusing, chlorine tablets and some shocks contain CYA. Dichlor and trichlor chlorine both have CYA added. Calcium hypochlorite (cal-hypo) shock does not.

The purpose of CYA is to prevent the sun from burning the free chlorine out of the water. Without a stabilizer, the sun may burn out your shock in just a few hours. As well as being combined into a few types of chlorine, CYA may also be added as a granule or liquid.

Here is the trouble with CYA. If you are using chlorine tablets, your CYA level should be around 30-40. But since tablets contain CYA, it is easy to let it get out of control. If it becomes too high then you have to drain water from the pool. In a salt pool, we keep CYA higher, up to around 80. Careful though because when CYA gets too high, the chlorine becomes ineffective. If it has become too high, the pool usually will become cloudy and light green. The common reaction is to add more chlorine, thinking that this will clear it up. Your chlorine level will then be high, but the pool will not clear up. The CYA level at this point is probably 150 or higher.

I have recently read that CYA actually concentrates near the surface, so I think that if you are draining water to lower CYA, you will benefit by removing it from the top. Lastly, CYA is the mystery chemical that 90% of people don’t know about or don’t understand. It is usually responsible when you can’t figure out why the pool just won’t clear up.

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Calcium Hardness

Let’s talk about calcium in your pool water. Why is it needed?

First of all, adding calcium is most important for a gunite pool. The plaster surface contains calcium and if the water is low in calcium, it will absorb the calcium from the pool surface. This causes the surface to degrade over time. Calcium is usually required in very large amounts. It is common to add 50 lbs. or more in small increments when starting a pool up for the season.

A few tips about calcium:

  • Water can only hold a certain amount of dissolved solids. This amount fluctuates with temperature and colder temperatures will hold more solids. Because of this, you may add a lot of calcium in the early spring and then when the water heats up it will drop out of the water and cover the floor with a white powder. For this reason, I recommend not maxing out the calcium level. Instead try to achieve a number in the middle of the acceptable range.
  • Don’t buy small amounts of calcium. Usually it is quite okay to add large amounts at a time. It takes a lot of calcium to raise the hardness level so buy it in a 50 lb. bag.
  • Keep a bulk 50 lb. bag of calcium chloride on hand during the winter. If we have any ice, use the calcium on your driveway or sidewalk to melt it.
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Today we will learn a little about total alkalinity. There is not much to know about it really.
The total alkalinity should be held between about 80 – 120. When kept in this range it acts as a very effective buffer for the pH. See my post about pH for more on this subject. If the alkalinity falls too low then the pH will drift around wildly. If the level becomes too high, the pH will remain high as well. The water will cause scaling, it will look cloudy, and algae will be more likely to grow.
Here are a couple of tips regarding alkalinity and pH. To decrease alkalinity, pour muriatic acid into the water in a column. To decrease the pH, splash the acid over the surface. Adding sodium bicarbonate to the water will increase pH and alkalinity.

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Controlling pH

This is the third post in my chemical series. Today I will discuss pH, what it is and how to control it.

pH is a number representing the acidity or alkalinity of your water. The preferred range for a pool is between 7.2 – 7.6. The lower the number, the more acidic the water is. We can lower the pH by adding an acid to the water and we can raise the pH by adding a base.

I have to discuss total alkalinity here briefly because of its effect on pH. We adjust alkalinity by adding sodium bicarbonate (baking soda) to increase it and muriatic acid to decrease it. These chemicals also affect the pH and I will get into that a little more in my next post. The important thing to understand about alkalinity at the moment is that it works as a buffer for the pH. In other words, if the alkalinity is at 0 and we try to lower the pH by adding a very small amount of muriatic acid to the water, the pH will descend well below 7.0. Again, with an alkalinity of 0, the same is true when we add a little soda ash. The pH will ascend way above 8.0. This is why the alkalinity is very important to controlling pH. It allows us to control the pH with precision.

To adjust pH down, we can add either a dry acid or muriatic acid. This may also lower the alkalinity, so it is important to retest the water several hours later. My advice on adjusting the pH up is to first determine if the alkalinity is low as well. If the alkalinity is low then raise it first with sodium bicarbonate or baking soda. This will also raise the pH and only then should you add soda ash if needed to raise the pH any more. Soda ash has a tendency to cloud the water, so I would not recommend it unless necessary.

You should check the pH often (once or twice a week). It is very important to your equipment, the pool surface, and yourself. A pool with a high pH is also more likely to grow algae. A low pH is very detrimental to your equipment’s rubber o-rings.

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I will take the next few days to expand on my previous chemical post. We will start off by looking at chlorine in a little more detail.
To begin, there are two chlorine tests. The really important one is free chlorine. This is the chlorine that oxidizes contaminates from the water. We want the level of free chlorine to be 1 – 3. The second test we can conduct is for combined chlorine. Combined chlorine is a bad form of chlorine and we need to eliminate it. Combined chlorine is responsible for chlorine odors, so if you smell the chlorine in your pool, you most likely have a high combined chlorine reading. To remove this bad chlorine from the water we shock the pool with a granular chlorine. The higher the combined chlorine level gets, the more shock is needed to eliminate it.

Check back soon for clarification of shock types.

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Five important chemical tests.

It seems everyone is out to sell you an entire suite of chemicals to maintain the water in your pool. I am here to tell you that many of those may be unnecessary and even cause problems.
The first critical thing to check is your free chlorine. It should be between 1 –  3 usually.
Second up is pH. This reading should be held between 7.2 – 7.6. Before adjusting pH up you should check the alkalinity. Sodium bicarbonate will raise both alkalinity and pH. When adjusting the pH down we use Muriatic acid. By pouring the acid in a column we can adjust the alkalinity down and by splashing it over the surface we lower the pH. You should always be very careful with Muriatic acid. It is extremely dangerous.
Third, we have alkalinity. Alkalinity acts as a buffer for our pH. If the alkalinity is maintained between about 80 – 120, our pH will remain stable. Let the alkalinity get too low and the pH will drift wildly.
Fourth on the list is calcium hardness. This is most important to gunite pools. The plaster or pebble surface will degrade quickly with a lack of calcium. Hardness levels between 200 – 400 are recommended.
Last we have cyanuric acid, also referred to as stabilizer or conditioner. This chemical is built into some chlorine shocks (dichlor and trichlor) and all chlorine tablets. You can also add it by itself. For the unsuspecting consumer, it is easy to get this level too high, into the hundreds. It should be kept around 30 – 40 (60 – 80 in a salt pool). The only way to reduce the level is by draining water.
Other tests can be important on a case by case basis, but if you have these five right, you are on the path to a clear, clean pool.

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