A high pH level indicates alkaline in the water. In order to reduce the pH levels, an acid, such as vinegar, should be added to the water until the desired pH level is reached.
- Measure the pH
Use a pH measuring kit to test the pH level of your water. Decide on the pH level that you desire. In most cases, water should be close to neutral, which is a pH of 7. However, many plants have an ideal watering pH level that is not neutral, so research your plant to find out its optimal level.
- Choose your acid
If the water is for drinking, be sure to use a non-toxic acid, such as white vinegar or citric acid. Water for plants can be lowered with small amounts sulphuric or phosphoric acid but only if the pH is exceptionally high.
- Add the acid carefully
Carefully add your chosen acid to the water. Do this slowly, and in small increments. It might help to get a pipette, and add the acid one drop at a time.
- Remeasure and continue to add until you reach the desired pH level
After every addition of acid, measure the pH level of the water. Continue to carefully add drops of the acid to the water until you reach your desired pH level.