When cyanuric acid is added to the pool, it increases the total alkalinity, but not the carbonate alkalinity, which is the alkalinity that matters in water balance.
The higher the CYA, the more aggressive the water. Why? Because CYA actually contributes to total alkalinity (it's called cyanurate alkalinity). To accurately calculate the LSI, we need to know the carbonate alkalinity, which requires removing the cyanurate alkalinity from the total alkalinity.
Test strips can be used to test total alkalinity. Total alkalinity is raised by adding stabilizer, soda ash, or baking soda. Total alkalinity is lowered by reducing pH and aerating your pool.
There are two ways to increase your swimming pools alkalinity level: sodium bicarbonate (baking soda) or any type of alkalinity increaser product. If you choose to purchase an alkalinity increaser product be sure the product is made from sodium bicarbonate, which is the main substance used to raise pH.
Clearly, when cyanuric acid is in the water, it overpowers pH in terms of controlling chlorine strength.
However, as the cyanuric acid levels increase, they will have an effect on the total alkalinity test result. The cyanuric acid/cyanurate system contributes to total alkalinity since total alkalinity is the sum of all titratable alkaline substances and cyanurate is a titratable alkaline substance.
All alkaline materials are buffers. Cyanuric acid happens to be the most common buffer found in pool water. In effect, cyanuric acid helps stabilize both chlorine and pH. It binds with chlorine to prevent photolysis and it keeps pH elevated.
The problem with low cyanuric acid is chlorine degrades quickly in the presence of sunlight. Chlorine is rendered completely ineffective within a few hours of sun exposure. If you didn't have cyanuric acid in your pool or it was low, you'll find that you need to add a lot more chlorine to have effective sanitization.
A rule of thumb is 1.5 lbs. of baking soda per 10,000 gallons of water will raise alkalinity by about 10 ppm. If your pool's pH tested below 7.2, add 3-4 pounds of baking soda. If you're new to adding pool chemicals, start by adding only one-half or three-fourths of the recommended amount.
Cyanuric acid is raised by adding chlorine stabilizer containing cyanuric acid. The only way to lower cyanuric acid is by replacing water.
Total Alkalinity, like pH, is affected by environmental factors. Rain, acidic sanitizers, addition of fill water and other product applications can all change the alkalinity over time. Total Alkalinity should be tested once every three to four weeks.
Alkalinity is the total alkaline material in your pool water. You should test alkalinity first because it will buffer pH. Your reading should be in the range of 80 to 120 parts per million (ppm).
Causes of Falling Alkalinity
Alkalinity levels can decrease for a wide range of reasons, which extend to: A high amount of rainwater entering the pool, which leads to the water being diluted. Acid rain can cause alkalinity levels and pH levels to drop. Sweat and even urine may cause alkalinity levels to lower.
The main reason for high CYA levels in your pool is from using too much stabilized chlorine. When the pool water evaporates, CYA remains in the water, much like other chemicals such as salt and calcium. As an example, 1 lb. of trichlor in a 10,000 gallon pool will raise the CYA level by 6 ppm.
What happens when CYA in a pool is too high? – CYA Levels exceeding a threshold of 70 parts-per-million of cyanuric acid can reduce the effectiveness of the chlorine in a pool. The amount of time it takes to kill bacteria lengthens as the concentration of CYA increases.
When cyanuric acid levels get too high, it can cause something referred to as chlorine lock, which basically means your chlorine has been rendered useless. You'll know it has happened when your chlorine test shows very or little chlorine even right after you've added it to the pool.
It's very normal to experience a drop in alkalinity levels in your pool over the season. For the most part, this is due to natural causes such as evaporation or agitation of your water. Throughout the hot summer season, your pool will release dissolved carbon dioxide (CO2) in a process known as 'water degassing'.
If your alkalinity level is too low, then your pool pH can fluctuate at the slightest addition of an acid or base. pH can drop randomly, which causes damages to pool walls, metal, and to swimmers. Therefore, it is important to routinely perform tests; we recommend once a week.
Causes of Falling Alkalinity
A decrease in pH can be caused by excessive rainwater entering the pool and diluting the water, acid rain which can directly drive both your pH and alkalinity levels down, and even bodily fluids from swimmers such as sweat and urine (oh yeah, it happens).
Saltwater pool manufacturers recommend maintaining cyanuric acid levels around 60-80 ppm. This is a bit higher than the 30-50 ppm range recommended for non-saltwater pools. And if you live in an area where your pool gets a lot of direct sunlight, you may even consider bumping your cyanuric acid up to 80-100 ppm.
Pools with very low or no cyanuric acid experience “chlorine demand,” or the inability to maintain chlorine levels. No matter how much chlorine you add, the levels drop quickly. Chlorine without CYA, also known as unstabilized chlorine, is destroyed by UV rays very quickly.
As mentioned earlier, it will take at least 48 hours and up to a week to fully dissolve. Powdered cyanuric acid is not so common and it may not be available to buy in your area. It's reported to not dissolve any faster than granular stabilizer.
Although there are no known adverse health effects associated with high CYA concentrations, most health officials usually limit CYA levels to 100 ppm. Some states recommend a lower level for spas, and some jurisdictions ban the use of CYA altogether.
You should keep your outdoor pool or spa's Cyanuric Acid level at 0-30 parts per million (PPM).