If the pool water pH value is not correct, you may experience a variety of negative effects. 

These may include reduced water disinfection, eye irritation, irritated and tender skin, calcium deposits in the pool, or corrosion damage on the pool ladder and other metal components. 

Start by measuring the pH value of your pool with Teststrips (insert link). The pool water pH value must be between 7.0 and 7.4. 
To lower the pH value, use pH-minus (insert link) To increase the pH value, use pH-plus (insert link). 

To make it easier to adjust the pH value in a larger pool, you can use an automatic EASY pH-regulator (insert link), which will automatically add the correct dose to the pool. 

Enjoy the water!