A backwater valve is a one-way safety device that stops sewage from flowing back from the public sewer into your building drains. It’s a common safeguard for basements, low-lying homes, and flood-prone properties, and it’s required by plumbing code in many situations.
NDS is a trusted leader in water management. Across residential and commercial jobs, NDS valves are known for durability, reliable backflow protection, and easy installation. Models include PVC and an ABS backwater valve option, with straightforward pipe connections that fit standard PVC pipe sizes; that means less time on site and fewer system issues.
Installed on the main building drain, the valve stays open for normal outflow and automatically closes when it senses reverse flow, keeping wastewater out of homes and commercial buildings during heavy rain or sewer surges. When sewer surges raise water pressure in the line, the flapper closes to block backflow and keep wastewater out. Many U.S. jurisdictions require backwater protection for fixtures below the next upstream manhole cover.
NDS models use durable PVC or ABS with a quick-action flapper for unrestricted uni-directional flow and a gasketed access cap that helps maintain a watertight seal. Sizes range from 2–6 inches, and components are corrosion-resistant for long service life and easier inspection/cleaning. The design maintains a tight seal even when connected to a pressurized system, while remaining open for normal flow.
Typical installs include residential basements, low-elevation commercial sites, healthcare and hospitality facilities with sensitive plumbing, and municipal projects that need added protection. Inspect and clean at least annually—many municipalities recommend semiannual checks—and follow local permit requirements.
Match valve size to your pipe (commonly 3", 4", or 6"), pick material (PVC or ABS) to suit the system, and confirm accessibility for maintenance. Inspect upstream piping for pipe corrosion or worn seats; damaged lines can prevent a full seal and shorten service life.
Backwater valves protect against sewer backup; “check valves” are general one-way valves and are not a substitute where code requires backwater protection. Always confirm compatibility with local codes and existing DWV piping.
Get fast shipping, expert support, and competitive pricing on in-stock NDS models. Shop NDS backwater valves at Maxx Drains’ collection page and outfit your project with proven, code-friendly protection.
Also see related products on our NDS drainage collection: Explore NDS drainage solutions.
