Short answer: In Suffolk County a failed cesspool must be replaced with at least a septic tank and leaching structure, approved by the Department of Health Services, and only a Liquid Waste License holder can do the work. Upgrading to an I/A system instead is optional for a straight replacement and is what the grants pay for. In Nassau, the town, city or village building department approves the job and the contractor needs a Home Improvement License.
Last updated: November 2026.
What you're allowed to install
| Option | Suffolk County | Nassau County |
|---|---|---|
| New cesspool | Not allowed as a replacement since July 1, 2019; barred in new construction since 1973 (SCDHS, 11/19/2024 presentation) | Ask your building department; we found no county rule on residential replacements |
| Septic tank + leaching ring(s) | The minimum for a replacement; SCDHS approval through your licensed contractor | Through the town, city or village; licensed contractor |
| I/A system + leaching | Optional for a straight replacement; required for qualifying construction since July 1, 2021 and by some town codes; grant-eligible | Optional; S.E.P.T.I.C. grant up to $35,000 per its administrator (county page: $20,000) |
| Connect to sewer | Only where a district serves the street | Most of Nassau is sewered; see the county list |
Town overlays in Suffolk: East Hampton requires a low-nitrogen system for any voluntary replacement; Southampton requires an I/A system for substantial upgrades SCDHS orders in its high-priority area. Details: Is an I/A system required?
Repair or replace? How Article 6 defines the work
OWTS Retrofit is a modification of an existing cesspool or system: replacing or adding a septic tank, grease trap, I/A components, lift or pump station, distribution box or manhole; replacing or adding leaching structures; or replacing piping, the control panel or pumps. OWTS Replacement is abandoning or removing the existing system and installing a new one. Neither can add bedrooms or change the use; that makes it a construction project with its own rules.
Since July 1, 2019 both need SCDHS approval. The county set up a simpler route: the licensed liquid waste contractor registers the job electronically before the work and submits what was installed afterwards. Article 6 excludes parcels inside a proposed sewer district approved by the Health Commissioner from the current-standards requirement for replacements and retrofits.
When a cesspool is considered failed
Article 6 defines a failed system by what it does, not its age. The conditions include:
- It keeps failing to accept wastewater from the house, or keeps discharging into the basement, a drain or a watercourse.
- Wastewater rises to the ground surface over or near the system.
- It needs pumping four or more times a year because groundwater gets in, a leaching structure collapsed or the leaching area is clogged. Scheduled maintenance doesn't count.
- Groundwater seeps back in after it is pumped.
- Structural damage confirmed by a NYS licensed design professional or a Liquid Waste License holder (an engineer's or architect's finding overrides a contractor's).
Suffolk's grant FAQ adds practical warning signs: slow drains, gurgling toilets, odors, and a system that needs pumping two or more times a year. It also notes that replacing an old block cesspool removes the uncertainty of if and when it will collapse. See signs your cesspool is failing and how long a cesspool lasts.
How a replacement goes in Suffolk
- Diagnosis. A licensed operator pumps and inspects; structural damage should be documented in writing (photos and receipts also support a grant application).
- Decide conventional or I/A. If you want grant money, apply before any work. Grants aren't issued for systems already installed.
- Approval. For a conventional replacement, the licensed contractor registers it with SCDHS. For an I/A system, a design professional or approved installer files with OWM.
- Abandonment of the old cesspool. The installer certifies abandonment of the old structure as part of closing out the job.
- Close-out. As-built documentation; for I/A, a witnessed start-up, registration and a maintenance contract.
Nassau County
Nassau's health department generally reviews larger projects (subdivisions and higher-flow commercial systems); single-family work runs through the local building department. Every contractor pumping, repairing or installing must hold a Nassau County Home Improvement License. When a system is taken out of service, Nassau has an abandonment procedure covering pumping, disposal and inspection before backfill. Details: Nassau County regulations.
What it costs
For I/A replacements there is real public data. SCDHS reported average installed costs of about $34,000 (East End) and $28,500 (West End) under the grant program, excluding engineering and site restoration, and the county's November 2025 installer sheet for a four-bedroom home shows a median quote of about $25,700 when the existing leaching rings can be reused. We found no public source for conventional septic-tank replacement prices on Long Island, so we don't print one. Full breakdown: cesspool and I/A costs. Grants: septic grants guide.
Frequently asked questions
Can I replace my cesspool with a new cesspool?
Not in Suffolk County. Since July 1, 2019 a replacement must meet current standards: at least a septic tank ahead of a leaching structure, approved by SCDHS. In Nassau, replacements go through your town, city or village building department and the contractor needs a Nassau County Home Improvement License; ask the building department what it will approve.
Is replacing a cesspool cover or ring a repair or a replacement?
Suffolk's Article 6 calls modifying an existing system an OWTS Retrofit, which includes replacing or adding a septic tank, leaching structures, piping or other components. Removing the old system and installing a new one is an OWTS Replacement. Both have needed SCDHS approval since July 1, 2019; your licensed contractor files it.
When does a Suffolk cesspool count as failed?
Article 6 lists conditions including sewage backing up or surfacing, groundwater seeping into the system after pumping, structural damage confirmed by a design professional or licensed contractor, and needing pumping four or more times a year because of groundwater, a collapsed structure or a clogged leaching area (routine maintenance excluded).
Who can replace a cesspool in Suffolk County?
Only a contractor holding an active Liquid Waste License under Suffolk County Code Chapter 563, Article VII. For grant-funded I/A work, the installer must also be on the county's SIP-approved list.
Sources
Each source was re-read on November 7, 2026. Program amounts and rules change; the agency page is the authority.
- Suffolk County DHS: Changes to wastewater practices effective July 1, 2019
- Suffolk County Sanitary Code, Article 6 (amended 12/1/2020)
- Suffolk County: Septic Improvement Program FAQ (4/2026)
- Suffolk County: Septic Improvement Program grant process overview (2026)
- Town of East Hampton Code §210-3-2 (low-nitrogen systems)
- Town of Southampton Code §123-52 (I/A OWTS required)
- Suffolk County DHS presentation, 11/19/2024 (hosted by the Town of Shelter Island)
- Suffolk County SIP: 4-bedroom installer cost ranking sheet (rev. 11/06/2025)
- Nassau County Soil & Water Conservation District: S.E.P.T.I.C. program (program administrator)
- Nassau County: Septic FAQ
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