During a cold snap, the pipes in your building freeze and burst. While doing a load of laundry, your washing machine overflows. A heavy rainstorm causes water to leak through the roof of your building--and you live on the top floor. Water damage occurs frequently, so it's a good idea to know what is (and isn't) covered by insurance.
Won't my landlord's insurance cover the damage?
Your landlord's insurance will provide coverage for damage to the building itself, but it won't provide coverage for damage to your personal property. And if your landlord's policy only provides coverage for damage to the exterior of the building (you can find this information in your rental agreement), it won't cover the cost of replacing pipes, carpeting, wall coverings, etc. inside your rental unit. (Depending on the circumstances, your landlord may still be liable for repairs, even if the damage is not covered by insurance.)
What about renters insurance?
A good renters policy will provide coverage for most water damage. Just make sure that it is specifically mentioned in the policy--that way both your damaged belongings and the cost to repair the rental unit itself (e.g., new pipes, carpeting, wall coverings) will be covered. One possible exception: whatever causes the water damage (e.g., dishwasher, washing machine) may not be covered by your renters policy if you failed to maintain it properly.
What if the water damage is the result of a flood?
Basic renters insurance doesn't provide coverage for water damage that is a result of a flood. If you live in a flood-prone area, you'll need to purchase a separate policy or add a rider onto your renters policy for this type of coverage.
What if I can't live in my apartment as a result of the water damage?
Most renters insurance policies will provide coverage for additional living expenses incurred if your rental unit is unlivable. In other words, the insurance company will pay for you to live at another location (at a price similar to your old apartment) while your apartment is being repaired.
Please note that this description/explanation is intended only as a guideline.