Voluntary flood insurance policies are not enforced until 30 days after purchase.
Overflows from sewer systems or sump pumps are not considered a flood unless a flood has caused the backup and overflow.
Flood insurance is required by law for some high risk homes but only a minority of homes fall under this category. Congress passed some laws requiring that all federally-insured or regulated lenders, for instance mortgages backed by Fannie Mae or Freddie Mac require flood insurance to protect their investment in the property.
Floods can happen anywhere and without warning. 25% of homes with flood claims each year are in low risk zones just like yours. Give yourself and your family the peace of mind of knowing that they are protected should a flood happen. It will take a full 30 days from the time your policy is purchased to be valid so waiting to make this decision is a serious risk.
Flood damage is not typically covered by a homeowners insurance policy.