What the calendar does to plumbing here
The first hard freeze. Every year the same two calls come in together: a split hose bib that was left connected to a garden hose over winter, and a burst line in a crawl space, garage or an exterior wall that was never insulated. Both are cheap to prevent in October and expensive in January. Disconnect the hoses, and if you have a crawl space, look at it before the cold arrives rather than after.
The thaw. A pipe that froze does not always burst while it is frozen — a good number let go as they thaw, which is why the damage often shows up on the first warm day rather than the coldest night.
Spring rain. Sump pump season. A pump that has sat dry since last year is a pump nobody has tested. Pour a bucket into the pit and confirm it starts, stops, and that the discharge is actually clear.
Summer humidity. Condensation on cold supply lines and toilet tanks drips onto ceilings and reads exactly like a leak. Worth ruling out before opening drywall.