Roof leaders and sump pumps tied into the sanitary sewer are not allowed
Updated October 30, 2026 · 3-minute read · Old House Sewer Lines
An illegal sump pump connection to the sewer is any pipe that sends rain or groundwater from a sump, roof leader or yard drain into a sanitary line. New York's plumbing code forbids it, and some Westchester towns check for it at sale.
The rule is § 1101.3 of the state plumbing code (PCNYS), in both the 2020 edition and the 2025 edition in force since December 31, 2025: storm water may not drain into sewers built for sewage alone (NYS DOS, 2025 Plumbing Code). Section 1101.2 says roof and paved-area runoff must go to an approved place of disposal. For one- and two-family homes, where approved, it may run out onto a lawn or street as long as it flows away from the building.
Where it is checked
Two places confirmed for this site, Rye and Mamaroneck village, require a discharge compliance certificate before a house is sold. To get one, a plumber licensed in Westchester County certifies that no culverts, drains, hoses, leaders, lines, pipes or pumps discharge into the sanitary sewer. Rye's building department says the point is to catch cracks and breaks and also sump-pump discharges, roof leaders and yard drains hooked into the lateral (Rye Building Department notice).
The Village of Mamaroneck tightened its version in 2024. Its plumber's certification must now identify every sump pump in the house and where each one discharges (Village of Mamaroneck Code § 282-13). A non-compliant lateral must be fixed within 60 days of notice, or the village may do the work and lien the cost. The penalty is up to $500 or 15 days, with each day a separate offense. Rye's law carries the same 60-day rule and penalty. Town-specific steps are in the Village of Mamaroneck certificate and Rye's lateral law.
Other towns may have their own sump and leader rules. Scarsdale's and Larchmont's ordinance text could not be confirmed, so ask the building department before assuming either way.
Why towns care
Every gallon of rain in a sanitary pipe takes up room meant for sewage. Westchester County's Sewer Act limits how much storm water and groundwater a town may send to county trunk sewers, which is explained in inflow and infiltration. The county's model agreement with Long Island Sound towns asked each to adopt a point-of-sale law banning storm water and sump pump connections (Westchester County DEF).
Mount Vernon's sewer management plan lists "Identify illegal sump pump connections" as a goal (Mount Vernon CMOM plan). The city also faces the reverse problem. Under a federal consent decree lodged September 19, 2023, it must fix its separate storm sewer system, which the city admitted has discharged untreated sewage into the Bronx and Hutchinson Rivers. Each illicit source it identifies must be removed within 30 days, or an action plan must go to EPA and the state (consent decree). More on the city is in Mount Vernon sewer laterals.
What to look for at home
Things worth checking include a sump pump hose run into a laundry sink or floor drain, a roof leader that disappears into the ground near the foundation, and a yard drain piped toward the house. A buried leader does not always end at the sewer; a licensed plumber can trace where it goes. Moving a discharge is plumbing work, and the town may require a permit.
Pump sizing and wiring are outside this site's scope.
Key facts
- Plumbing Code of New York State § 1101.3 keeps storm water out of sewage-only sewers, in the 2020 and 2025 editions (NYS DOS).
- Under § 1101.2, one- and two-family homes may, where approved, discharge runoff onto lawns or streets if it flows away from the building.
- Rye and Village of Mamaroneck sale certificates require a county-licensed plumber to certify no leaders, pumps or drains feed the sanitary sewer (Rye notice).
- Since 2024 the Village of Mamaroneck plumber must list every sump pump and its discharge point (Village Code).
- Mount Vernon's sewer plan sets a goal to find illegal sump pump connections (CMOM plan).