Water or air pressure tests on piping systems must be held for not less than _____ minutes.

For water or air pressure tests on piping systems, the required duration is a critical factor in ensuring the integrity and safety of the plumbing installation. Holding the test for at least 15 minutes allows adequate time for any potential leaks to manifest, providing sufficient opportunity to identify weaknesses or failures in the system.

This length of time is standardized to ensure that the test is effective in detecting leaks which could lead to water damage or system inefficiencies over time. A shorter duration may not allow for the necessary observation, potentially resulting in undetected issues that could compromise the plumbing system post-installation. Thus, the requirement of a minimum of 15 minutes is established in plumbing codes to ensure thorough testing and long-lasting reliability of piping systems.