Short answer: The county's sewer map shows no active district inside Smithtown; on-site systems are the norm apart from any village-run or private plant the layer doesn't include.
Smithtown in numbers
| Town | Town of Smithtown |
|---|---|
| Area | 12.03 sq mi |
| In active sewer district | under 1% |
| In proposed district | 2% · Smithtown Collection System Boundary |
| Groundwater zone | Zone VIII 83%, Zone I 17% |
| FEMA flood zone | 2% |
| One-family lots / median | 7,597 / 0.49 ac |
| One-family lots outside active sewer districts | about 7,597 |
Computed 2026-11-07 from Suffolk County GIS (hamlet boundaries, sewer districts, groundwater management zones, FEMA flood zones, protection areas, tax parcels). Shares are of land area; a district boundary is not a hookup, and some village-run systems are missing from the county layer. Method and full table.
Sewer coverage
The county's sewer map shows no active district inside Smithtown; on-site systems are the norm apart from any village-run or private plant the layer doesn't include. A sliver (2%) is inside a proposed district (“Smithtown Collection System Boundary”). By parcel count, roughly 7,597 of Smithtown's 7,597 one-family lots sit outside an active district; that is the local cesspool and septic population, before counting unconnected lots inside districts. For comparison, the nearest places: Village of the Branch (0% sewered, median lot 0.51 ac); Kings Park (5% sewered, median lot 0.24 ac); Hauppauge (26% sewered, median lot 0.34 ac). By active-sewer share Smithtown ranks 63 of the 165 Suffolk hamlets and villages we measured.
Groundwater, lots and flood exposure
Groundwater management Zone VIII (83%) and Zone I (17%): Article 6's minimum lot for a new home on an on-site system here is 20,000 sq ft, unless the density is met another way or an exemption applies. County parcel records show 7,597 one-family lots touching Smithtown, with a median of 0.49 acres (about 21,200 sq ft), above that minimum and the 62nd-largest median lot in our Suffolk table. 2% of the land is in FEMA's 1%-annual-chance flood zone.
For most Smithtown homes the main running cost is pumping; when a cesspool fails, the replacement must include at least a septic tank, and grants can cover most of an I/A system.
Who handles what in Smithtown
- Building and electrical permits: Town of Smithtown
- System approvals and grants: SCDHS, 631-852-5700 (permits) / 631-852-5811 (grants)
Frequently asked questions
Is Smithtown on public sewer?
Generally not: no active county sewer district covers Smithtown on the county's map.
Can Smithtown homeowners get septic grants?
Yes, if the home isn't sewered and isn't in a proposed sewer district: up to $20,000 from Suffolk and up to $25,000 from the state.
County rules, licensing and grant steps: Town of Smithtown overview, septic grants, replacement rules. More in Smithtown: Kings Park, Hauppauge, Commack, Nesconset.
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 Sanitary Code, Article 6 (amended 12/1/2020)
- Suffolk County: Septic Improvement Program information
- Suffolk County: SIP property eligibility lookup
Need cesspool or septic work in Smithtown?
Submit a request with your address. We match it to an independent, licensed Suffolk County operator who serves that address; the operator confirms the time and price with you.
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