Sewer systems connect populations to wastewater collection and treatment, but the available measures differ. This overview separates U.S. publicly owned treatment works, global wastewater treatment, European urban treatment connections and historical collection-system condition estimates.
Key Sewer System Statistics
The most useful headline figures span coverage, treatment, investment and system condition:
- In January 2022, 17,544 publicly owned treatment works served 270.4 million Americans in the United States.
- In 2022, POTWs served an estimated 82% of the U.S. population through centralized public systems.
- In 2022, 233.6 million Americans, or about 70% of the U.S. population, received secondary or advanced treatment from POTWs.
- In 2022, 139.3 million people received advanced wastewater treatment in the United States.
- In 2022, 3.8 million people received less-than-secondary treatment from U.S. POTWs.
- Over a 20-year horizon beginning January 1, 2022, U.S. clean-water infrastructure needs totaled $630.1 billion in 2022 dollars.
- In the 2022 U.S. survey, conveyance repair needs were $110.1 billion.
- In the 2022 U.S. survey, new conveyance needs were $41.0 billion.
- From 2012 to 2022, reported conveyance needs rose 27%, from $118.7 billion to $151.1 billion in 2022 dollars.
- In the 2022 U.S. survey, combined sewer overflow correction needs were $36.5 billion.
- In the 2022 U.S. survey, sanitary sewer overflow elimination needs were $26.6 billion.
- In 2022, 107 countries reported some wastewater statistics, representing 73% of the world’s population.
- In 2022, an estimated 42% of household wastewater was not safely treated before discharge worldwide.
- In 2022, 113 billion cubic metres of household wastewater were released with inadequate or no treatment, according to a global estimate.
- In the European Union, the share connected to at least secondary urban wastewater treatment rose from 68% in 2000 to 80% in 2020.
- In 2023, 81% of the EU population was connected to at least secondary urban wastewater treatment.
- In 2024, Denmark’s connection share was 98% for at least secondary urban wastewater treatment.
- In a 2009 U.S. EPA assessment, approximately 40,000 sanitary sewer overflow events occurred per year.
- In that 2009 assessment, approximately 50,000 sewer breaks occurred per year.
- In that 2009 assessment, approximately 500,000 sewer stoppages occurred per year.
Contents
- U.S. sewer system scale and population served
- U.S. sewer infrastructure investment needs and trends
- Combined and sanitary sewer overflow statistics
- Global wastewater treatment coverage
- European sewer connection trends
- Sewer condition, failures and data limitations
U.S. Sewer System Scale and Population Served
The U.S. Environmental Protection Agency’s 2022 Clean Watersheds Needs Survey counted publicly owned treatment works, or POTWs, as a measure of centralized public wastewater treatment. It is not interchangeable with the number of sewer connections because decentralized systems, including private septic systems, are outside this measure.
The survey counted 17,544 POTWs in January 2022, serving 270.4 million Americans. EPA estimated that these systems served 82% of the U.S. population, using 2020 Census population and centralized treatment reporting. 2022 Clean Watersheds Needs Survey Report to Congress
Treatment levels provide another view of coverage:
- About 70% of the U.S. population, or 233.6 million people, were served by POTWs with secondary or advanced treatment in 2022.
- Advanced wastewater treatment served an estimated 139.3 million people in 2022.
- An estimated 3.8 million people were served by less-than-secondary treatment in 2022, about 1% of the total U.S. population.
- In 1972, almost 60 million people were served by less-than-secondary treatment, an historical EPA comparison using the same treatment category.
These figures describe centralized treatment service, not the share of households physically connected to a sewer pipe. They also mix observed counts with estimates based on population and treatment reporting.
U.S. Sewer Infrastructure Investment Needs and Trends
EPA’s 2022 survey reported $630.1 billion in total clean-water infrastructure needs over the next 20 years, measured in January 2022 dollars. The figure is a reported needs estimate, not completed spending, debt or a verified funding shortfall.
| 2022 survey category | Reported need | Scope |
|---|---|---|
| Secondary wastewater treatment | $66.6 billion | Centralized treatment |
| Advanced wastewater treatment | $83.6 billion | Centralized treatment |
| Conveyance system repair | $110.1 billion | Existing collection and conveyance |
| New conveyance systems | $41.0 billion | New conveyance |
| Combined sewer overflow correction | $36.5 billion | CSO correction |
| Decentralized wastewater treatment | $74.7 billion | Includes non-sewer systems |
| Water reuse | $7.7 billion | Reuse infrastructure |
The repair and new-conveyance categories together totaled $151.1 billion in 2022. EPA reported that this was up 27% from $118.7 billion in 2012, while advanced-treatment needs rose 36%, from $61.5 billion to $83.6 billion, an increase of $22.1 billion. 2022 Clean Watersheds Needs Survey Report to Congress
Secondary-treatment needs changed less over the same period, increasing 3% from $64.9 billion in 2012 to $66.6 billion in 2022. Related stormwater-management needs were $115.3 billion in 2022, up 385% from 2012; stormwater is related infrastructure, not sanitary-sewer-only spending.
Combined and Sanitary Sewer Overflow Statistics
Combined sewer overflows, or CSOs, and sanitary sewer overflows, or SSOs, represent different wastewater-system problems. EPA’s 2022 survey reported CSO correction needs of $36.5 billion, down 39%, or $23.0 billion, from 2012 to 2022.
Thirty-five states reported CSO correction needs in the 2022 survey. The largest named state totals were:
- New York: $6.0 billion.
- Pennsylvania: $4.4 billion.
- New Jersey: $3.6 billion.
- Connecticut: $2.9 billion.
- Indiana: $2.9 billion.
Per-capita reported needs varied among jurisdictions reporting CSO needs:
| Jurisdiction | Reported CSO need per capita, 2022 |
|---|---|
| West Virginia | $922 |
| Connecticut | $817 |
| District of Columbia | $575 |
| Rhode Island | $534 |
| Indiana | $431 |
EPA reported $26.6 billion in needs to eliminate SSOs, equal to 8% of the wastewater-needs denominator used in the survey. Collection-system corrections accounted for 81% of reported SSO elimination needs; the treatment-plant portions included $2.5 billion for secondary treatment and $2.6 billion for advanced treatment.
The reported decline in CSO needs may reflect the mix of planning documents as well as infrastructure progress. 2022 Clean Watersheds Needs Survey Report to Congress
Global Wastewater Treatment Coverage and Sewer Data
Global wastewater statistics are constrained by uneven reporting. In 2022, 107 countries reported some wastewater statistics, representing 73% of the world’s population, but a calculable some-level treatment measure was available for only 73 countries representing 42% of the global population.
Among those 73 countries, an estimated 76% of total wastewater received some level of treatment. For the stricter definition of safe treatment—at least secondary treatment—only 42 countries, representing 12% of the global population, had calculable data, and those countries safely treated 60% of total wastewater.
WHO’s global estimates also indicate the scale of untreated household flows:
- Forty-two percent of household wastewater was not safely treated before discharge in 2022.
- An estimated 113 billion cubic metres of household wastewater were released with inadequate or no treatment in 2022.
- Industrial wastewater treatment data came from 22 countries representing 8% of the global population.
- In those 22 countries, 38% of industrial wastewater was reported as treated and 27% as safely treated in 2022.
WHO explicitly notes that the underlying data are insufficient for complete global wastewater statistics. These estimates should not be presented as a complete worldwide sewer-connection rate. Progress on the proportion of domestic and industrial wastewater flows safely treated
European Sewer Connection and Treatment Trends
Eurostat tracks connection to at least secondary urban wastewater treatment, which is a treatment-service measure rather than a direct count of household sewer connections. The EU share rose from 68% in 2000 to 80% in 2020, then reached 81% in 2023.
| Country or region | Earlier period and share | Later period and share |
|---|---|---|
| European Union | 2000: 68% | 2023: 81% |
| Belgium | 2000: 41% | 2024: 85% |
| Bulgaria | 2000: 36% | 2024: 67% |
| Czechia | 2005: 73% | 2024: 87% |
| Denmark | Not supplied | 2024: 98% |
Six EU countries reached at least 95% connection to at least secondary treatment in recent data through 2024: Denmark, Germany, Greece, the Netherlands, Austria and Sweden. Eurostat’s collection is voluntary, includes country data gaps and uses mixed reference years, so comparisons should retain those qualifications. Water statistics
Sewer Condition, Failures and Data Limitations
A separate EPA condition assessment provides historical context for U.S. collection systems. The 2009 assessment identified more than 19,500 sanitary sewer collection systems serving an estimated 150 million people; its scope differs from the 2022 POTW count.
The assessment reported that some U.S. sewers were more than 100 years old. It also estimated approximately 40,000 sanitary sewer overflow events, 50,000 sewer breaks and 500,000 sewer stoppages per year.
Approximately 75% of the nation’s piping systems were reported to be operating at 50% capacity or less in that assessment. These are historical estimates from 2009, not current national measurements, and the capacity characterization should not be interpreted as a present-day failure rate. Condition Assessment of Wastewater Collection Systems
Across the sources, the central limitation is definitional: POTW service, sewer connection, wastewater collection, treatment level and overflow events measure different parts of the system. The global and European figures also carry explicit reporting gaps, while EPA’s infrastructure figures describe capital needs over a 20-year horizon rather than actual expenditure.