A standard US homeowners policy — the HO-3 form most people have — covers water damage that is sudden and accidental. It excludes damage that developed gradually, and it excludes flood no matter how sudden.
Those three words do nearly all the work in a claim decision.
Sudden and accidental
A supply line to the washing machine bursts. A water heater tank splits. A pipe freezes and cracks. In each case the escape is abrupt, and the resulting damage to floors, drywall, and contents is covered.
Note what is covered and what is not: the policy pays for the damage the water caused, not for the failed part. A burst water heater means the flooring and drywall are paid for; the heater itself usually is not.
Gradual, seepage, and the exclusion that catches people
Most policies exclude damage from water that has been leaking "continuously or repeatedly" over a period — commonly worded as 14 days or more. A slow drip under a sink that rotted the cabinet base over a year is excluded. So is a shower pan that has been wicking into the subfloor since the bathroom was remodeled.
This is the most common denial, and it is decided by evidence rather than argument. Adjusters look at staining patterns, the extent of rot, and whether material has degraded in a way that takes time. A crisp wet edge with sound material behind it reads as sudden. Crumbling, discolored, layered staining reads as long-term.
Flood is a different policy entirely
Flood — surface water from outside entering the building, including storm surge and overflow of any body of water — is excluded from every standard homeowners policy in the country. Coverage comes separately, through the NFIP or a private flood carrier, and it carries a 30-day waiting period before it takes effect.
Sewer and drain backup is also excluded by default and is usually available as an inexpensive endorsement. It is the single most worthwhile add-on for a finished basement, and most people do not have it.
What the distinctions look like in practice
| Cause | Typically covered |
|---|---|
| Burst supply line | Yes |
| Water heater tank failure — the damage | Yes |
| Water heater tank itself | No |
| Pipe frozen while heat was on | Yes |
| Pipe frozen in a house left unheated | Often denied |
| Slow leak under a sink, discovered late | No |
| Roof leak from storm damage | Usually yes |
| Roof leak from worn shingles | No |
| Groundwater through a basement wall | No — flood or none |
| Sewer backup | Only with the endorsement |
The steps that protect a claim
Insurers can reduce or deny payment for damage that got worse because the homeowner did not act. That obligation is real and it is written into the policy as a duty to mitigate.
- Stop the water and photograph everything before touching it. Wide shots and close shots, with the source visible.
- Report it promptly. Delay is the second most common reason for reduced payment.
- Start drying, do not gut the house. Emergency mitigation is covered. Demolition performed before the adjuster has seen the loss is a fight you may not win.
- Keep every receipt, including fans you rented and hotel nights if the house is unlivable.
- Keep the failed part. The burst hose is the evidence that the loss was sudden. It gets thrown away constantly and it is the single most useful object in the file.
Mitigation versus repair
Water claims move in two stages, and they are priced differently. Mitigation is the emergency work — extraction, equipment, removal of unsalvageable material — and it is billed against a standard industry price list. Repair is putting the building back, and it is a normal construction estimate.
Mitigation invoices get scrutinized closely because equipment days are easy to inflate. This is exactly why daily moisture logs matter: they are the evidence that each day of equipment was necessary.
The short version
Sudden and accidental is covered; gradual is not; flood needs its own policy and 30 days of lead time. If a basement is finished, buy the backup endorsement now — it costs little and it covers the loss most likely to happen.