The answer to 'when to replace P-trap' is that you should replace your P-trap whenever it becomes damaged, worn out, or no longer functions properly. P-traps are the curved section of pipe underneath your sink that helps prevent sewer gases from entering your home. Over time, they can become clogged, cracked, or corroded, which can lead to leaks and other plumbing issues.
As a general rule, you should inspect your P-trap every 3-5 years and replace it if needed. Signs that it's time to replace the P-trap include frequent clogs, water leaks, foul odors, or visible damage to the pipe. If you notice any of these issues, it's best to call a professional plumber to assess the situation and determine if the P-trap needs to be replaced.