A concealed water pipe or tank subject to freezing must be installed at least how many inches in depth?

The correct answer is based on the necessity to prevent pipes from freezing. Water pipes and tanks that are concealed and at risk of freezing should be buried below the frost line, which varies by geographical location. In Kentucky, the minimum depth to protect against freezing is typically determined to be 18 inches, as this is generally adequate to keep the system insulated from colder temperatures experienced during winter months.

Choosing a depth of 18 inches ensures that even during extreme frosts, the ground temperature remains above freezing at that depth, thus preventing the water from freezing inside the pipe. Going deeper, such as 24 inches or 30 inches, would indeed provide additional safety but is not required according to the established codes for most plumbing applications in Kentucky. Adhering to the 18 inches standard strikes a balance between protection and practicality, as it remains within appropriate construction practices and cost-effectiveness.