Short answer: About 4% of Lake Grove lies inside Stony Brook Sewer District; everywhere else, wastewater stays on the lot.
Lake Grove in numbers
| Town | Town of Brookhaven |
|---|---|
| Village | Village of Lake Grove |
| Area | 2.94 sq mi |
| In active sewer district | 4% · Stony Brook Sewer District |
| In proposed district | 1% · Middle Country Road |
| Groundwater zone | Zone I 100% |
| FEMA flood zone | 0% |
| One-family lots / median | 3,056 / 0.30 ac |
| One-family lots outside active sewer districts | about 2,838 |
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
About 4% of Lake Grove lies inside Stony Brook Sewer District; everywhere else, wastewater stays on the lot. A sliver (1%) is inside a proposed district (“Middle Country Road”). By parcel count, roughly 2,838 of Lake Grove's 3,056 one-family lots sit outside an active district; that is the local cesspool and septic population, before counting unconnected lots inside districts. Next door: Centereach (8% sewered, median lot 0.31 ac); St. James (4% sewered, median lot 0.27 ac); Nesconset (3% sewered, median lot 0.32 ac). By active-sewer share Lake Grove ranks 46 of the 165 Suffolk hamlets and villages we measured.
Groundwater, lots and flood exposure
Groundwater management Zone I: 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 3,056 one-family lots touching Lake Grove, with a median of 0.30 acres (about 13,200 sq ft), below that minimum and the 101st-largest median lot in our Suffolk table. 7% is in a Special Groundwater Protection Area.
For most Lake Grove 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 Lake Grove
- Building permits: Village of Lake Grove
- Sewer: Stony Brook Sewer District
- System approvals and grants: SCDHS, 631-852-5700 (permits) / 631-852-5811 (grants)
Frequently asked questions
Is Lake Grove on public sewer?
Partly: about 4% is inside Stony Brook Sewer District; the other 96% relies on cesspools, septic tanks and I/A systems.
Can Lake Grove 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 Brookhaven overview, septic grants, replacement rules. More in Brookhaven: Centereach, Lake Ronkonkoma.
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 Lake Grove?
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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