How does dilution affect the pH of a basic solution?

The pH of a basic solution is greater than 7. Dilution decreases the pH of a basic solution. 

Dilution is a process in which water or another solvent is added to a solution to lower the concentration. As you keep adding more water and diluting the solution, the solution becomes more and more like pure water and the pH also keeps becoming increasingly closer to the pH of pure water, which is pH 7. A basic solution has more hydroxide ions than hydrogen ions, while an acidic solution possesses more hydrogen ions than hydroxide ions. When a basic solution is diluted by adding water to it, the concentration of hydroxide ions decreases, and the pH decreases. As more water is added, the solution becomes incrementally less alkaline and the pH keeps decreasing progressively towards 7.