When comparing sudden and accidental water-loss events, sewage backups pose one of the most serious health concerns, and insurers should understand the potential liabilities associated with these losses, especially when concrete is involved. In particular, current sewage restoration practices, concrete's porosity, and whether current guidance for sewage restoration is sufficient to return the concrete surfaces to a pre-loss condition should be carefully considered.

Policy language for water backups covers sudden and accidental losses from backups through sewers or drains or water overflows from devices intended to divert water from the foundation. To be a covered loss, however, the sewers, drains, and sump pumps must be located within the dwelling or on the resident's premises. This is the key question following a sewage loss. Backups that originate from the municipal waste treatment plant, lift stations, and sanitary sewer line maintenance located outside the property boundary typically are not covered events.

According to U.S. News and World Reports (June 2000), there are an estimated 400,000 sewer backups and 40,000 sanitary sewer overflows (SSO) that occur in the U.S. each year. Despite notable improvements made by municipalities, the frequency of sewage backups remains a serious problem.