How it works
- SettlingWastewater from the house settles in the first chamber, like a septic tank.
- TreatmentA blower adds air so bacteria convert ammonia to nitrate, and then (in low-oxygen zones) to harmless nitrogen gas.
- LeachingThe treated water goes into leaching rings or a pressurized shallow drainfield.
- Alarm and serviceEach system has an alarm and is registered with the County, with a required maintenance contract.
Approved technologies
Nassau's SEPTIC program accepts Hydro-Action AN, Norweco Singulair TNT and Hydro-Kinetic, Orenco AdvanTex AX20, Fuji Clean CEN and SeptiTech STAAR. Suffolk maintains its own Article 19 list of systems with general or provisional approval, which must reach 19 mg/L total nitrogen or less. Which one fits depends on your lot, groundwater and house size. Your design professional and installer choose from the approved list.
What it costs to own
| Item | Typical | Notes |
|---|---|---|
| Installed price (before grants) | $15,000–$30,000+ | East End reporting: $35,000–$40,000, $50,000+ with landscaping or a well move |
| Grants | Up to $45,000 (Suffolk) / $20,000 (Nassau) | Plus town rebates in Southampton, East Hampton and Shelter Island |
| Maintenance, years 1–3 | Covered | Funded by the County SIP grant |
| Maintenance, year 4+ | About $300/yr | The Peconic Estuary Partnership has announced up to $500/yr reimbursement in its area; check availability |
| Electricity | Modest, continuous | A small blower or pump runs all the time |
Is it worth it? See the out-of-pocket math and the full cost guide.
Who can install one
In Suffolk, grant-funded I/A systems must be installed by a company on the County's SIP-Approved Installer List (40 companies as of September 2026), and maintained by a provider with an I/A maintenance endorsement on their liquid waste license. In Nassau, the installer needs a Nassau County HIC license. We only work with installers who meet those requirements for grant jobs.
Town grants and sewer districts
Whether a grant applies, how much, and whether you're even eligible (sewer districts are excluded) depends on your town. Start with yours:
Frequently asked questions
What is an I/A septic system?
"I/A" means Innovative and Alternative Onsite Wastewater Treatment System (I/A OWTS). It's a septic system with a treatment unit that uses bacteria and air to remove nitrogen before the water goes into the ground. Suffolk requires approved systems to reach 19 mg/L total nitrogen or less in their treated water.
Which brands are approved?
Nassau's SEPTIC program accepts Hydro-Action AN, Norweco Singulair TNT and Hydro-Kinetic, Orenco AdvanTex AX20, Fuji Clean CEN and SeptiTech STAAR. Suffolk keeps its own Article 19 list of systems with general or provisional approval. Your installer and designer pick from those lists; we don't recommend brands.
Does an I/A system need electricity?
Yes. Most units run a small blower or pump continuously, so there's an electrical hookup (Southampton even requires a Certificate of Electrical Compliance for its rebate) and a modest ongoing electric cost.
What happens if it breaks?
The County SIP grant funds the first three years after installation. After that you need an annual maintenance contract with a provider who holds a Suffolk liquid waste license with an I/A maintenance endorsement. The contract covers inspections and alarms.
Is an I/A system required?
In Suffolk, for new construction and major renovations since July 1, 2021. For a failed system on an existing home, it's voluntary under County code, but it's the only type the grants pay for.
Sources
- Suffolk County SIP Homeowner Process Overview (2026) and Septic Improvement Program page
- Suffolk County Septic Improvement Program page (SSRP: up to 75%, not to exceed $25,000)
- Suffolk County Executive: new streamlined septic grant application, up to $45,000 (Aug 2026)
- Suffolk County SIP-Approved Installer List (revised Sep 14, 2026)
- Nassau County SEPTIC program (accepted technologies)
- Suffolk County Sanitary Code Article 19 (I/A OWTS)
- Peconic Estuary Partnership I/A Maintenance fact sheet (May 2024)
Related services
- Cesspool Replacement: Replacing an old block, brick or ring cesspool with a code-compliant system, and deciding between a conventional septic and a grant-funded I/A system.
- Cesspool to Septic Conversion: The conventional path: a septic tank ahead of leaching rings. When it makes sense, what it costs, and what it means for grants later.
- Cesspool Collapse & Backups: Sinking ground, a cave-in or sewage backing up. Safety first, then the fastest legal route to a replacement, and how to document the failure for a grant.
- Cesspool Inspection for Home Sales: Buying or selling a house on a cesspool: what a real evaluation includes, what a dye test can't tell you, and how to negotiate a replacement.