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2015 Assessment of Onsite System Installations

Onsite Wastewater Installation Assessment:
2015 Report

Map of the United States showing response to the survey by all states except NV, AZ, NH and the District of Columbia. 

Onsite wastewater systems have been and will continue to be a viable option for the treatment of wastewater in areas not served by centralized wastewater treatment systems. Every state in the nation has a population served by decentralized (onsite) wastewater systems. However, the extent to which this treatment option is being utilized has not been measured nationally since the 1990 Census.

NESC, with support of industry and state regulators, has been working to gather recent data (2015 through 2018) on the installation of onsite wastewater treatment systems across the country. The first of two reports, focuses on 2015 data. If you would like to receive a copy of the report, please send an email to . A second report will be available later this year (2020) assessing the use of onsite wastewater treatment systems with new residential and commercial development during the time frame of 2015 through 2018.

Knowledge of the current trends and the status of existing onsite wastewater treatment systems (OWTS) will provide local, state, and federal government agencies with necessary information to appropriately allocate resources to ensure necessary environmental and human health protections. Manufacturers and contractors may utilize the report findings to identify market trends, opportunities, and potential coverage gaps.

National Summary

Eighty-two percent (82%) of state regulatory/permitting agencies provided OWTS permit information for the year 2015. This response rate excludes partial responses to the  2015 Onsite Wastewater Installation Assessment. Figure 1 breaks down local-level response rates, by state, ranging from 100% to no response.

Map of the US showing state response rates at six different levels with the majority at a high to total response rate

Figure 1: Response rates to the 2015 Onsite Wastewater System Installation Assessment.

The assessment was broken down by the size of regulated OWTS. Participants were given the option to select if they regulate: 1) single-family, residential onsite wastewater systems only; 2) large (e.g., multi-family, commercial, institutional), onsite wastewater systems only; or 3) both single-family, residential and large, OWTS. The report shows 85% of the survey respondents regulate both single-family and large, OWTS; 11% regulate large OWTS only; and 4% regulate only single-family, OWTS. Many states have multiple agencies to regulate OWTS.

Onsite system permitting authorities vary from state to state and vary within a state depending upon system size, type, and/or physical location. Figure 2 depicts responses received from state regulatory agency representatives when asked to identify the level of government issuing OWTS permits within their respective state. Responses ranged from state-level to building departments having oversight of OWTS permits, with county-, state-, and city/county-level health agencies representing the vast majority.

Graph showing onsite system permitting authorities with most being county, state or health departments   

Figure 2: Breakdown of OWTS permitting authorities/agencies across the United States.

Given the range of jurisdictions (i.e., level of government) regulating OWTS, it is a difficult task for state agencies to collect permit data. When asked if permit data is tracked, 56% of the state representatives responding stated system permits are tracked. Of those respondents, 54% track permits with self-developed databases, 31% use spreadsheets, and the remaining 15% use purchased databases such as Digital Health Department or Health Space.

Roughly 54% (1,691 of 3,149) of the permitting jurisdictions across the U.S. provided OWTS permitting data.A total of 262,648 new and repair onsite system installation permits were issued in 2015 by the responding jurisdictions.

New onsite systems (associated with new housing or commercial construction) accounted for 59% of the permits issued in 2015, repair/replace permits accounted for 41% of the permits issued in 2015.Note some jurisdictions do not record repair installations and unfortunately, not all states distinguish between single-family OWTS and large OWTS.

Figure 3 provides a breakdown by type of permit (new installation, repair/replace) of OWTS permits issued. The "combined permits" category represent data from those states that do not distinguish between single-family OWTS and large OWTS. Of the permits issued in 2015 for new OWTS installations, 57% were for single-family systems, 42% were for single-family or large systems, and 1% were specifically for large systems. Concerning repair/replacement permits issued in 2015, the vast majority of systems repaired or replaced were for single-family OWTS.

Graph showing that the majority of 2015 on-site system permits issued for both new installations and repair/replace were for single-family systems with the second most being combined permits.   

Figure 3: OWTS permits issued for 2015 by type.

Not all responding permitting jurisdictions provided reasons for OWTS repairs. Of those responding, single-family OWTS repairs accounted for 15% of repair permits issued and large OWTS repairs accounted for 22% of repair permits issued in 2015. Repairs to both the septic tank and drainfield represented the largest category of repairs for single-family and large OWTS, 47% and 51%, respectively, as shown in  Figure 4.

Graph of 2015 on-site system repair breakdowns for both single-family and large systems showing the majority being for tank and drain field and the second most for drainfield.   

Figure 4: Breakdown of 2015 OWTS repair permits by system size.

If interested in obtaining an electronic copy of the full report, please email NESC at