What is the pressure testing requirement for a hydronic system before backfilling?

The correct answer is based on the requirements set forth in the North Carolina Mechanical Code regarding the pressure testing of hydronic systems. For hydronic systems, the code typically mandates a pressure test to ensure that the system is sealed and can withstand the operational pressures without leaks. A minimum pressure of 100 psi is necessary for this testing prior to backfilling.

This pressure level is intended to confirm the integrity of the piping and fittings under anticipated working conditions. If the pressure requirements were set lower, there might be insufficient assurance that small leaks would be detected, potentially leading to issues once the system is operational. Therefore, 100 psi serves as a reliable baseline to help confirm the system’s readiness and safety.

In contrast, the other pressure values listed (50 psi, 75 psi, and 125 psi) do not meet the requirements as established by the code. A lower pressure may not adequately expose potential leaks, while a higher pressure could exceed the design specifications of certain system components. Thus, 100 psi strikes a balance that is compliant with the code and effective in ensuring the system's reliability.