When New York's code requires a backwater valve
Updated October 30, 2026 · 2-minute read · Old House Sewer Lines
New York's backwater valve code requirement turns on elevation. Under §714.1 of the state plumbing code, fixtures on a floor below the manhole cover of the next upstream public-sewer manhole need a backwater valve, fitted on the building drain or on the horizontal branch that carries their waste.
The rule appears in both the 2020 Plumbing Code of New York State and the 2025 edition, which took effect December 31, 2025 (NYS DOS). It applies across southern Westchester, which follows the state code rather than New York City's.
Reading §714.1
The logic is simple. If the public sewer fills to the top of the nearest upstream manhole, sewage will seek any lower opening, and a basement floor drain, toilet or laundry sink below that rim is such an opening. The code's answer is to protect those low fixtures only.
The same section adds a limit. Fixtures above the manhole-cover elevation "shall not discharge through" the valve, except in existing buildings (PCNYS chapter 7). In new work, upstairs plumbing should bypass it, so the valve guards only the fixtures at risk and the rest of the house keeps draining when it shuts. In an older house, the exception lets a plumber put the valve on a line that also carries upper-floor fixtures.
| Section | What it says |
|---|---|
| §714.1 | Fixtures below the next upstream manhole cover need a backwater valve |
| §714.1 | Fixtures above that level may not drain through it, except in existing buildings |
| §714.2 | Valve must meet ASME A112.14.1, CSA B181.1 or CSA B181.2 |
| §714.3 | Working parts must be accessible |
Standard and access
Section 714.2 lists three product standards, ASME A112.14.1 or the Canadian CSA B181.1 and B181.2. Section 714.3 requires that the valve be installed so its working parts can be reached. That access rule is one reason valves usually sit in a covered pit or a floor box. Owner upkeep is covered in backwater valve upkeep.
Finding the elevation
Homeowners rarely know the rim height of the manhole up the street. A licensed plumber can establish it, and the city, town or village public works or engineering office may hold sewer maps. Never lift a manhole cover or look down into a sewer structure to check; NIOSH treats every manhole as a confined space that may hold a hazardous atmosphere. See why no one should enter a manhole.
Installing a valve is plumbing work that needs a permit, and in Westchester that means a county-licensed plumber. FEMA notes that the finished valve is part of the owner's lateral, not the town's (FEMA). How the different valve designs behave is set out in how a backwater valve works.
Local programs
A state pilot has paid for valves in one city. The Governor's office reported in April 2025 that Mount Vernon's Healthy Homes pilot, a $3 million state effort, had fitted backflow prevention devices, among other repairs, in 24 lower-income homes in areas at high risk of backflow (NY Governor). No open application process was described. Other local rules are gathered on the backups topic page and in the 2025 code changes.
The manhole-cover test
- Above the rimFixtures above the next upstream manhole cover: no valve required for them
- Below the rimFixtures below the next upstream manhole cover need a backwater valve
Video from Wilson County Government, an outside channel: A county chief inspector uses a diagram to show a valve is needed when the floor sits below the next upstream manhole. Nothing loads from YouTube until you press play.
Key facts
- Under §714.1, any fixture lower than the rim of the nearest upstream public manhole needs valve protection (ICC).
- Fixtures above that level may not discharge through the valve, except in existing buildings.
- Valves must meet ASME A112.14.1, CSA B181.1 or CSA B181.2 (§714.2), with accessible working parts (§714.3).
- The 2025 state plumbing code took effect on December 31, 2025, replacing the 2020 edition (NYS DOS).
- Mount Vernon's Healthy Homes pilot put backflow prevention devices in 24 homes (NY Governor).