Backflow Prevention and RPZ Testing in NYC and Long Island

Backflow is water flowing the wrong way, from a building back into the public water supply. Backflow preventers stop that from happening, and in New York City and on Long Island many properties are required to install and test them.

What is backflow?

Normally, water flows from the street main into the building. Under certain conditions, such as a sudden pressure drop from a water main break or firefighting, pressure in the building can exceed pressure in the main. Water can then be pushed or siphoned backward. If that water has been in contact with chemicals, boilers, irrigation systems, or process equipment, it can contaminate the supply.

A cross-connection is any point where the drinking water system connects to something that could contaminate it. Backflow preventers protect against cross-connections.

Common types of backflow preventers

• Reduced Pressure Zone (RPZ) assembly. Provides a high level of protection for high-hazard situations. It has two check valves and a relief valve that discharges water if pressure conditions are wrong, so it needs a drain and must be installed where discharge will not cause damage.
• Double Check Valve Assembly (DCVA). Two check valves in series, used for lower-hazard situations such as many fire sprinkler systems.
• Pressure Vacuum Breaker (PVB). Common on lawn irrigation systems.

The required type depends on the hazard level, which the water supplier and code determine.

NYC requirements

DEP requires backflow prevention on water service connections for many types of properties, including buildings with fire sprinkler or standpipe systems and properties with hazardous uses. According to DEP:

• Property owners must hire a Licensed Master Plumber to install a backflow prevention device, and plans may need DEP approval first.
• After installation, the device must be tested by a New York State certified backflow tester, and the test report (Form GEN-215B) must be submitted to DEP within 30 days of installation.
• The device must then be tested every 12 months, with the report signed by a Licensed Master Plumber.
• DEP sends a notification when the annual test is due. Failure to test can result in fines or water service disconnection.

Internal devices protecting fixtures and equipment inside the building fall under DOB plumbing code requirements.

Long Island requirements

On Long Island, cross-connection control is enforced by water suppliers under the New York State Sanitary Code. Your water district or authority will tell you whether your property needs a device, what type, and how to submit annual test results. Irrigation systems, commercial properties, and buildings with fire sprinkler systems commonly need devices.

What happens during a test

A certified tester connects a test kit to the device's test cocks and checks that each check valve holds and, for an RPZ, that the relief valve opens at the right point. The test usually requires briefly shutting off water. If the device passes, the tester completes the report. If it fails, it must be repaired or replaced and retested.

Common problems

• Discharge from an RPZ relief valve can mean a fouled check valve or pressure fluctuations.
• Freezing. Devices installed outdoors or in unheated spaces need protection.
• Debris from water main work can lodge in check valves.
• Access. Devices installed too high, too low, or in tight spaces are hard to test and repair.

Planning a new installation

When adding a backflow preventer, plan for:

• Enough space for testing and maintenance.
• A drain sized for RPZ discharge.
• Freeze protection.
• Pressure loss. Backflow preventers reduce pressure, which can matter in taller buildings or where pressure is already low.
• An expansion tank on the hot water system if the device creates a closed system.

Keep records

Keep copies of approvals, test reports, and repair records. Put the annual test date on your calendar so you are not waiting for a reminder letter.

From commercial buildings in Manhattan and Brooklyn to irrigation systems in Nassau and Suffolk, backflow prevention is a routine but important part of protecting drinking water.

This article is general information for property owners, not legal or engineering advice. Rules and procedures change; confirm current requirements with the agency or utility involved.