How is water hardness of 11 GPG expressed in Mg/L?

To convert water hardness from grains per gallon (GPG) to milligrams per liter (Mg/L), it's important to understand the relationship between the two units. Water hardness is primarily measured by the concentration of calcium and magnesium ions in water, and one grain per gallon of hardness is equivalent to approximately 17.1 Mg/L.

In this specific question, the water hardness of 11 GPG can be converted to Mg/L by multiplying the value in GPG by 17.1. Therefore, the calculation would be:

11 GPG × 17.1 Mg/L per GPG = 188.1 Mg/L.

This calculation clearly shows that the water hardness of 11 GPG corresponds to 188.1 Mg/L when converted, which aligns perfectly with the correct answer. Understanding this conversion is essential for water operators, as it allows them to assess water quality and necessary treatment processes accurately.