Short answer: About 0% of the Town of Southold's land is inside an active sewer district on the county map; about 12,707 of 12,707 one-family lots in the town's hamlets and villages sit outside any active sewer district. There is no town septic rebate, so the county and state grants are the funding.
Last updated: November 2026. Data computed 2026-11-07 from Suffolk County GIS; rules and programs re-read November 7, 2026.
Town of Southold in numbers
| Land in active sewer districts | 0% |
|---|---|
| Land in proposed districts | 0% |
| Places with ~0% active sewer | 13 of 13 hamlets and villages |
| One-family lots outside active districts | about 12,707 of 12,707 |
| Groundwater zones (land share) | Zone IV about 100% |
| I/A systems installed (Oct 2024) | about 308, 6% of the county's 5,344; 4th of the ten towns |
| Town septic rebate | No |
| Town code on I/A systems | None found beyond the county rules |
Sewer districts and where the cesspools are
- Active districts: none on the county layer inside the town's hamlets and villages.
By one-family lot count, the most lots outside an active district are in Southold (about 3,557), Mattituck (about 2,222), Cutchogue (about 1,898), Greenport West (about 1,095), East Marion (about 785). Median one-family lots run from 0.17 acres in Greenport to 1.15 acres in Fishers Island. In 3 of 11 places the median lot is smaller than Article 6's minimum for a new home on an on-site system in its main zone. Across the town, about 17% of the land is in FEMA's 1%-annual-chance flood zone; 12% is in a Special Groundwater Protection Area.
What the Town of Southold adds
- Rebate: none listed by the county as of November 7, 2026.
- Town code: no town-wide I/A mandate found beyond the county rules as of November 7, 2026.
- Building department: Town of Southold; villages with their own: Greenport.
Every hamlet and village in the Town of Southold
Land-area shares inside county sewer-district polygons; zone = main Article 6 groundwater zone; flood = FEMA 1%-annual-chance zone; lot = median one-family lot (acres). Linked names have their own page. Some village-run systems are missing from the county layer. Full table: sewer coverage by hamlet.
| Hamlet / village | Active sewer | Proposed sewer | Zone | Flood | Median lot (ac) |
|---|---|---|---|---|---|
| Cutchogue | 0% | 0% | Zone IV | 9% | 0.73 |
| East Marion | 0% | 0% | Zone IV | 11% | 0.49 |
| Fishers Island | 0% | 0% | Zone IV | 29% | 1.15 |
| Greenport (village) | 0% | 0% | Zone IV | 16% | 0.17 |
| Greenport West | 0% | 0% | Zone IV | 26% | 0.34 |
| Laurel | 0% | 0% | Zone IV | 4% | 0.52 |
| Mattituck | 0% | 0% | Zone IV | 8% | 0.52 |
| New Suffolk | 0% | 0% | Zone IV | 40% | 0.36 |
| Orient | 0% | 0% | Zone IV | 46% | 0.62 |
| Peconic | 0% | 0% | Zone IV | 7% | 0.63 |
| Plum Island | 0% | 0% | Zone IV | 38% | n/a |
| Robbins Island | 0% | 0% | Zone IV | 11% | n/a |
| Southold | 0% | 0% | Zone IV | 16% | 0.50 |
County rules apply on top: no cesspool-for-cesspool replacement since July 1, 2019, and an I/A system for new homes and major reconstruction since July 1, 2021. Details, licensing and grants: Suffolk County overview.
Frequently asked questions
How much of the Town of Southold is on sewer?
About 0% of the land in the town's hamlets and villages is inside an active county sewer district, and 0% inside proposed districts; about 12,707 of 12,707 one-family lots in the town's hamlets and villages sit outside any active sewer district. A district boundary is not a connection.
Does the Town of Southold have a septic rebate?
No town rebate is listed by Suffolk County as of November 7, 2026. Southold homeowners use the county grant (up to $20,000) and the state grant (up to $25,000); the town had about 308 I/A systems by October 2024.
Who issues building permits for septic work in Southold?
The Town of Southold building department, except in the incorporated villages (Greenport), which run their own. SCDHS approves the sanitary system itself.
Sources
Each source was re-read on November 7, 2026. Program amounts and rules change; the agency page is the authority.
- Suffolk County GIS Viewer map service (hamlets, villages, sewer districts, groundwater zones, flood zones, tax parcels)
- Suffolk County DHS presentation, 11/19/2024 (hosted by the Town of Shelter Island)
- Suffolk County DHS: Changes to wastewater practices effective July 1, 2019
- Suffolk County: Septic Improvement Program information
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