Plenty of things affect acidity levels in Swimming Pools. Rain can do this, as acid rain affects it. Certain things that you place on your garden, for example insecticides or pesticides with acidic components can run off into the swimming pool. Also, if something acidic ends up in the air, it can dissolve or at least land into the pool changing it. Bird droppings can also change it (possibly). However, there needs to be a lot of these factors combined to change the overall acidity by a large amount and most of the time it should be ok.
Remove some water in container (10-20%) and add new water. example: pump water high in cyanuric acid out of a swimming pool and the add fresh water to the pool.
Muriatic Acid
The only way to lower your cya level in your swimming pool is to partially drain your pool and fill with fresh water that will lower it or if you want to lower it to almost nothing completely drain your pool and start over but keep in mind chlorine tablets will raise your CYA level More information in the related link below.
Muriatic acid
Usually you would add muriatic acid to adjust the pools acid level.
Using sodium bicarbonate to lower pH in a swimming pool is not effective. Sodium bicarbonate, or baking soda, is typically used to raise pH levels in pools. To lower pH in a pool, an acid such as muriatic acid or sodium bisulfate should be used.
.03g/L or 30 ppm or 1 lb for 3800 gallons (14400 liters)
Soda Ash
No, muriatic acid is used to lower pH and total alkalinity levels in pool water, not to raise cyanuric acid levels. To raise cyanuric acid levels, you would typically use cyanuric acid stabilizer or conditioner.
Reduces alkalinity of swimming pool water (softens hard water)
One efficient way to heat a swimming pool and maintain comfortable temperatures for swimming is to use a pool heater. Pool heaters can be powered by electricity, gas, or solar energy, and can quickly raise the water temperature to a desired level. Additionally, using a pool cover when the pool is not in use can help retain heat and prevent heat loss, further ensuring comfortable swimming temperatures.
To raise the acidity in your pool, you need to add a chemical called muriatic acid or sodium bisulfate. Start by testing the pool's pH level to determine how much acid is needed. Dilute the acid in a bucket of water before adding it to the pool to avoid damage to the surfaces. Always follow the manufacturer's instructions and ensure proper safety precautions when handling these chemicals.