How much acid is needed to reduce water alkalinity?

To limit the upward climb of your growing medium's pH, acid may need to be injected into your water to reduce excess alkalinity. Water alkalinity is a measure of the carbonates and bicarbonates in the water and acts just like limestone in the growing medium.

The higher the alkalinity, the more “limestone” that is applied at each irrigation and the faster the pH of your growing medium increases. So, at what point is it necessary to inject acid into a water source to reduce alkalinity?

Why is the growing medium's pH rising?
As plants uptake fertilizer, the roots release acids (hydrogen ions) and bases (hydroxyl ions) to maintain a neutral charge within the plant's roots. This is why fertilizers are labelled with a potential acidity or basicity that predicts how the plant will react with the fertilizer.

When the plant cannot generate enough acid from fertilizer uptake to neutralize the water alkalinity in the growing medium, this causes the growing medium's pH to climb. Therefore, acid injection is needed to neutralize excess water alkalinity or “limestone” in the water.

Read more at the PRO-MIX website