Short answer: No active county sewer district covers Brentwood on the county's GIS layer, so homes here use cesspools, septic tanks or I/A systems unless a village or private plant serves them.
Brentwood in numbers
| Town | Town of Islip |
|---|---|
| Area | 10.95 sq mi |
| In active sewer district | 0% |
| In proposed district | 2% · Brentwood |
| Under feasibility study (not a district) | 24% · Heartland Sewer Feasibility Study Area |
| Groundwater zone | Zone I 66%, Zone VII 34% |
| FEMA flood zone | 0% |
| One-family lots / median | 9,147 / 0.25 ac |
| One-family lots outside active sewer districts | about 9,147 |
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
No active county sewer district covers Brentwood on the county's GIS layer, so homes here use cesspools, septic tanks or I/A systems unless a village or private plant serves them. A sliver (2%) is inside a proposed district (“Brentwood”). Another 24% is inside “Heartland Sewer Feasibility Study Area”, which the county map marks as under feasibility study: that is not a district, proposed or otherwise, so it doesn't by itself affect grant eligibility. Counting lots instead of land: about 9,147 of the 9,147 one-family lots touching Brentwood lie outside any active sewer district, and those homes rely on on-site systems. Neighbouring areas: North Bay Shore (0% sewered, median lot 0.27 ac); Baywood (0% sewered, median lot 0.37 ac); Central Islip (23% sewered, median lot 0.23 ac). By active-sewer share Brentwood ranks 154 of the 165 Suffolk hamlets and villages we measured.
Groundwater, lots and flood exposure
Groundwater management Zone I (66%) and Zone VII (34%): 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 9,147 one-family lots touching Brentwood, with a median of 0.25 acres (about 11,000 sq ft), below that minimum and the 127th-largest median lot in our Suffolk table. 25% is in a Special Groundwater Protection Area.
For most Brentwood 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 Brentwood
- Building and electrical permits: Town of Islip
- System approvals and grants: SCDHS, 631-852-5700 (permits) / 631-852-5811 (grants)
Frequently asked questions
Is Brentwood on public sewer?
Generally not: no active county sewer district covers Brentwood on the county's map.
Can Brentwood 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 Islip overview, septic grants, replacement rules. More in Islip: Central Islip, Bay Shore, Islip.
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 Brentwood?
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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