The short version: water claims turn on three distinctions, sudden versus gradual, water versus flood, and the path the water took. Slow leaks are routinely denied as gradual damage, flood requires separate coverage, and seepage through foundations is usually excluded. The clock matters too: reporting fast and documenting everything is half the claim.
Sudden and accidental versus gradual
A burst pipe on Tuesday is sudden and accidental. A pipe that has been seeping under a sink since spring is gradual, and gradual damage is excluded in most policies. The covered part is often the sudden failure itself and resulting damage, not the pipe, and not mold that grew because the leak went unnoticed.
Flood is a different product
Ground water rising into your home is flood, covered only by separate flood insurance. Water that entered through a wind-damaged roof is a wind claim. Carriers sometimes characterize water incorrectly in the first pass; the entry path is a fact worth photographing.
Documentation beats memory
Photograph the source, the path, and every wet surface before extraction. Keep moisture readings if remediation takes any. Save every receipt for mitigation; carriers owe reasonable emergency mitigation costs, but only when they are documented.