State of Sewage Backups in the United States (2025)

May 5

Sewer backups, instances where wastewater reverses flow into buildings, pose serious risks to public health, property, and municipal infrastructure. In 2025, the United States continues to grapple with both sanitary sewer overflows (SSOs) into the environment and backups into homes and businesses. This article examines the prevalence, causes, economic and regional impacts, regulatory landscape, and emerging strategies to mitigate sewer backups nationwide.

Prevalence and Trends

National SSO Volume: The U.S. Environmental Protection Agency (EPA) estimates between 23,000 and 75,000 sanitary sewer overflows occur each year across the country, events in which raw sewage is discharged from collection systems into streets, waterways, or basements.
Annual SSO Estimate Update: More recent EPA regional data indicate at least 40,000 SSOs annually, underscoring persistent challenges in sewer collection system management and operation.
Urban Hotspots: In New York City alone, the Department of Environmental Protection recorded an average of 449 backups per fiscal year (FY2020–FY2024), a 5% increase over FY2019–FY2023. Of these, 54% were due to heavy rainfall, 33% to grease blockages, 9% to debris, and 4% to other causes.

Causes and Contributing Factors

Increased Precipitation & Climate Variability: Heavier and more frequent storms overwhelm combined and sanitary systems, driving rainwater infiltration that outpaces treatment capacity.
Aging Infrastructure: According to the American Society of Civil Engineers (ASCE) 2025 Report Card, U.S. wastewater infrastructure earned a D+, reflecting decades of underinvestment and deferred maintenance.
Blockages: Common obstructions include tree root intrusion, grease accumulation in building lateral lines, and “flushable” wipes clumps. Blockages remain a leading cause of backups into structures.
System Design & Capacity Deficits: Combined sewer systems, prevalent in older Northeastern urban areas, are prone to overflow during wet weather, while inadequate conveyance diameters in expanding suburbs fail to handle growth-driven loads.

Economic Impact

Homeowner Damage Costs: Uninsured sewer backup events can cost homeowners $20,000–$50,000 per incident. Many standard homeowners policies cap sewer-backup coverage at around $5,000, often with deductibles of $2,500 or more.
Insurance Claims: Water-damage related claims, including those triggered by sewer backups, are filed by approximately 14,000 U.S. residents each day, translating to about 1.6% of insured homes annually.
Restoration Expenses: Typical water-damage restoration runs from $1,342 to $6,044, with severe cases exceeding $15,000, not accounting for potential mold remediation and structural repairs.
Preventative Investments: Adding sewer-backup endorsement coverage costs homeowners on average $150–$300 per year, though premiums can reach $700 in high-risk areas. Installation of backflow preventers and sump pumps likewise add upfront costs but can substantially reduce risk.

Regional Variations

Northeast Urban Centers: Cities with legacy combined sewer systems, such as Boston, Philadelphia, and parts of New England, experience the highest frequency of SSOs and backups during storm events.

Aging Suburbs & Rural Areas: Municipal trunk line deterioration and private lateral failures in older suburbs compound backup risks. In rural zones, malfunctioning septic systems can similarly cause overflows, though these fall outside public sewer SSO statistics.

Flood-Prone Regions: Gulf Coast and Midwest communities face dual threats from heavy rainfall and storm surge, necessitating both stormwater management and sewer system upgrades.

Regulatory and Insurance Landscape

EPA Oversight: Under the Clean Water Act’s National Pollutant Discharge Elimination System (NPDES), SSOs that reach water bodies are prohibited without permit authorization. Enforcement actions target municipalities failing to maintain proper collection system operation.
Building Codes & Local Ordinances: Some states and municipalities now require backflow prevention devices on building sewer laterals; however, adoption is uneven across jurisdictions.
Insurance Coverage Gaps: Standard homeowners policies exclude sewer backups, necessitating optional endorsements. Policy limits and high deductibles leave many homeowners exposed to out-of-pocket expenses.

Prevention and Mitigation Strategies

Asset Management & Condition Assessment: Regular CCTV inspections, flow monitoring, and vulnerability assessments enable targeted rehabilitation before failures occur.
Green Infrastructure: Bioswales, permeable pavements, and green roofs reduce stormwater entering combined sewers, alleviating peak flows.
Household Protections: Installing backwater valves, maintaining sump pumps, and educating homeowners about proper waste disposal can prevent lateral backups.
Policy Incentives: Insurance premium discounts for homes equipped with backflow prevention devices encourage broader adoption.

Future Outlook

The convergence of aging infrastructure, climate-driven precipitation extremes, and continued urban growth underscores an urgent need for sustained investment. The EPA’s Clean Watersheds Needs Survey estimates $630 billion in clean-water infrastructure funding will be required over the next two decades, with over half designated for wastewater systems alone. Without accelerated capital spending and innovative management approaches, sewer backups and SSOs will remain a persistent challenge for utilities, governments, and homeowners alike.