The four systems, side by side
| Cesspool | Septic system | I/A system | Sewer | |
|---|---|---|---|---|
| What it is | A pit (block, brick or precast rings) that takes everything | A sealed tank, then leaching rings | A septic system plus a treatment unit that removes nitrogen | Pipes to a treatment plant |
| Treats the waste? | Barely | Settles out solids | Removes most nitrogen | Yes, at the plant |
| Can you install a new one on Long Island? | No | Yes (the code minimum for replacements in Suffolk) | Yes (required for new construction in Suffolk) | Only where a district exists |
| Grants? | No | No | Yes: up to $45,000 in Suffolk, $20,000 in Nassau | Separate sewer projects |
| Ongoing costs | Pumping | Pumping every few years | Maintenance contract (~$300/yr after year 3) plus electricity | Sewer tax/charge |
How to tell which one you have
- Check your tax bill. A sewer district charge usually means you’re connected to sewer. No sewer charge usually means a cesspool or septic system.
- Look at the age of the house. Suffolk banned cesspools in new construction in 1973. A house built before then that’s never had its system replaced very likely has a cesspool.
- Find the covers. A cesspool usually has one or more round covers over rings. A septic system has a tank cover near the house and separate leaching covers further out. An I/A system has a treatment-unit lid, an alarm, and usually an electrical connection.
- Ask for records. The County Health Department and your town building department may have records of a replacement or I/A registration. Every I/A system has to be registered.
- Have it opened. A pump-out with a look inside is the definitive answer, and it tells you the condition too.
Nearly 70% of Suffolk homes are on cesspools or septic systems, according to the County Executive. In Nassau, about 90% of the county is sewered, but most of the North Shore isn’t.
Why the difference matters so much here
Long Island drinks from the aquifer under it, and its bays take the rest. A 2011 study attributed 69% of the nitrogen in the Great South Bay to cesspools and septic systems. Neither cesspools nor conventional septic systems remove much nitrogen, and that’s the whole reason I/A systems exist and the grants only pay for them.
Which should you choose when yours fails?
- In a sewer district, or a proposed one? You’re not eligible for the septic grant, and you may be connecting to sewer instead. Check first. More: is your house in a sewer district?
- Grant-eligible and able to wait for the grant to be issued? Price an I/A system first. With up to $45,000 from Suffolk County and New York State, it’s often cheaper out of pocket than a conventional system. Try the grant estimator.
- Not eligible, or can’t wait? A conventional septic system is the legal minimum: about $10,000–$25,000. See cesspool to septic conversion.
A new cesspool isn’t on the list. That option ended for good in Suffolk in 2019. Details: cesspool laws on Long Island.
Need it done? See cesspool to septic conversion on Long Island. Town grants & sewer districts: Brookhaven, Oyster Bay.
Sources
- Suffolk County: wastewater practice changes effective July 1, 2019
- Suffolk County Sanitary Code Article 19 (I/A OWTS)
- Save the Great South Bay: cesspools, septics and the Great South Bay (69% of nitrogen)
- Suffolk County Executive (Aug 2026): nearly 70% of Suffolk homes use cesspools and septic systems
- Nassau County SEPTIC program (accepted I/A technologies)