Why this is the first thing to check
Both grant programs exclude sewered areas:
- Suffolk SIP: the house must be on a cesspool or septic system, “not connected to a sewer system or located within a proposed sewer district.”
- Nassau SEPTIC: the property must not be connected to a sewer or located in an existing or proposed sewer district, unless the district documents site constraints that prevent connection.
The word that catches people is proposed. You can be on a cesspool today, with no sewer pipe on your street, and still be ineligible because a sewer project is planned for your area. Find that out before you pay a design professional.
Does Suffolk County have sewers?
Some. The County Executive’s office says nearly 70% of Suffolk homes use cesspools or septic systems. Sewers are concentrated in the western towns, village downtowns and a few large districts, and several expansion projects have been underway:
| Project | Where | What it means for you |
|---|---|---|
| Southwest Sewer District (District 3) | Parts of the Towns of Babylon and Islip, plus a small area of Huntington | If your home is connected, you’re not on septic |
| Carlls River expansion | Parts of Deer Park, North Babylon, West Babylon, Wyandanch and West Islip (2,184 homes, plus 1,489 never-connected homes in District 3) | Inside it, connect to sewer, not a septic grant |
| Forge River | Mastic–Shirley, from just west of the William Floyd Parkway east to the Forge River (~1,900 parcels) | Inside it, no septic grant |
| Smithtown and Kings Park downtowns | The downtown business districts, via Sewer District No. 6 | Surrounding neighborhoods stay on septic |
| Northport waterfront | The village’s last unsewered waterfront area (~$10,000 per house to connect, per the village) | Inside it, connecting replaces the septic decision |
And Nassau?
About 90% of Nassau is sewered. The big exception is the North Shore: most of it is still on cesspools and septic systems, including many villages around Manhasset Bay, Hempstead Harbor and Oyster Bay. If you’re on the South Shore (Hempstead, Massapequa, Long Beach), you’re very likely on sewer already.
How to check your address
- Look at your property tax bill. A sewer district line item usually means you’re in one.
- Ask the County. In Suffolk, the Department of Public Works handles sewer districts, and the grant program’s questions go to the Department of Health Services at (631) 852-5811. In Nassau, contact the SEPTIC program at (516) 364-5861.
- Ask your town or village about planned sewer projects, especially near a downtown or on the water.
- Ask the installer. Experienced local installers know which streets are in or near a district, but get the official answer in writing before you rely on it.
If you’re in a district
- If you’re connected, you don’t have a cesspool problem. You have a sewer bill.
- If you’re in a proposed district and your cesspool is failing, a conventional septic replacement may be the sensible bridge. See cesspool to septic conversion.
- If you’re outside any district, you’re clear on this rule. Next: the Suffolk grant guide or the Nassau grant guide.
Need it done? See cesspool replacement on Long Island. Town grants & sewer districts: Brookhaven, Islip, Huntington, Smithtown, Oyster Bay.
Sources
- Suffolk County Executive (Aug 2026): nearly 70% of Suffolk homes use cesspools and septic systems
- Suffolk County DPW: Sewer District No. 3 (Southwest) expansion feasibility study
- Suffolk County SIP Homeowner Process Overview (2026): not sewered or in a proposed sewer district
- Nassau County SEPTIC program: sewer district exclusion and exception
- Governor's office: Forge River and Carlls River sewer construction (2021)
- Greater Long Island: Carlls River sewer expansion (Deer Park, North/West Babylon, Wyandanch, West Islip)
- NYSDEC ENB: Smithtown downtown sewering, extension to Sewer District No. 6
- TBR News Media: sewering Northport's waterfront (~$10,000 per house to connect)
- Hempstead Harbor Protection Committee: most of Nassau's North Shore is on cesspools