Riverhead, NY Cesspool & Septic: Sewer, Rules, Grants

Short answer: Only part of Riverhead is sewered.

Riverhead in numbers

Town	Town of Riverhead
Area	15.13 sq mi
In active sewer district	18% · Riverhead Sewer District
In proposed district	0%
Groundwater zone	Zone IV 67%, Zone III 33%
FEMA flood zone	3%
One-family lots / median	3,624 / 0.24 ac
One-family lots outside active sewer districts	about 2,221

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

Only part of Riverhead is sewered. The county layer puts about 18% of its area inside Riverhead Sewer District; homes outside that line use on-site systems. By parcel count, roughly 2,221 of Riverhead's 3,624 one-family lots sit outside an active district; that is the local cesspool and septic population, before counting unconnected lots inside districts. Next door: Riverside (0% sewered, median lot 0.30 ac); Baiting Hollow (0% sewered, median lot 0.53 ac); Aquebogue (0% sewered, median lot 0.57 ac). By active-sewer share Riverhead ranks 28 of the 165 Suffolk hamlets and villages we measured.

Groundwater, lots and flood exposure

Groundwater management Zone IV (67%) and Zone III (33%): Article 6's minimum lot for a new home on an on-site system here is 40,000 sq ft in Zones III, V and VI, unless the density is met another way or an exemption applies. County parcel records show 3,624 one-family lots touching Riverhead, with a median of 0.24 acres (about 10,700 sq ft), below that minimum and the 130th-largest median lot in our Suffolk table. Also mapped: 3% of the land is in FEMA's 1%-annual-chance flood zone; 52% is in a Special Groundwater Protection Area.

For most Riverhead 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 Riverhead

Building and electrical permits: Town of Riverhead
Sewer: Riverhead Sewer District
System approvals and grants: SCDHS, 631-852-5700 (permits) / 631-852-5811 (grants)

Frequently asked questions

Is Riverhead on public sewer?

Partly: about 18% is inside Riverhead Sewer District; the other 82% relies on cesspools, septic tanks and I/A systems.

Can Riverhead 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 Riverhead overview, septic grants, replacement rules. More in Riverhead: Aquebogue, Calverton, Wading River.

Sources

Each source was re-read on November 7, 2026. Program amounts and rules change; the agency page is the authority.

Need cesspool or septic work in Riverhead?

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.

Request Service →