Unexpected water in your basement can damage walls and floors, destroy carpeting, ruin furniture, and lead - pretty quickly - to mold. And perhaps the most upsetting of all: As these places are so often used for storage, a wet basement can ruin irreplaceable items like photo albums, antiques, and family heirlooms. When you experience a flooded basement for the first time, it's imperative to determine if the water problems are going to recur or if it was a one-time event. Can you safely leave your property downstairs once you've got the mess cleaned up? Or does everything need to come upstairs immediately? What's certain is that if water in your basement is a consistent problem, it's time to start making decisions. Determining where the water is coming from is the first and most essential step in solving this problem. Beyond observable flooding around your home and in your neighborhood, there are four common sources of water entering basements: Surface water running down foundation walls. Groundwater in water-saturated soils being pushed into the basement by hydrostatic pressure. Storm sewer water from the municipal storm sewer system backing up into the home's existing perimeter foundation drain and leaking into the basement. Sanitary sewer water from a clog in your home's sewer line, the municipal sewer line, or the combined municipal storm/sanitary sewer system backing up into the home's drain system, causing sewer water to come up through sink drains and floor drains on lower levels. Each source has its own specifics and requires it own course of action. Find out more about your home's drainage system by consulting a contractor or plumber.