The answer to 'when to replace P-trap' is that you should typically replace a P-trap every 3-5 years or if it becomes damaged or clogged. P-traps are the curved pipe under your sink that helps prevent sewer gases from entering your home. Over time, they can corrode, crack, or accumulate buildup that restricts water flow.
Signs it's time to replace a P-trap include slow draining, persistent odors, or visible damage. Replacing a P-trap is a relatively simple DIY project, but you may want to call a plumber if you're uncomfortable working with plumbing fixtures or suspect a more complex issue.