The Short Answer
- 01Who: buildings whose water use could contaminate the city supply, including those with roof tanks, chillers, large or treated boilers, irrigation, or more than one service line, and many businesses such as restaurants, laundries, and medical offices.
- 02Annual test: every device is tested at least once every 12 months by a tester certified by the NYS Department of Health, and the GEN215B report goes to DEP.
- 03New devices: a PE or RA designs the installation for DEP approval, a licensed master plumber installs it under a DOB permit, and the first test report is due within 30 days.
- 04Device type follows the hazard: an RPZ or air gap where contamination could make people sick, a double check valve where it would only affect taste, odor, or color.
- 05Missing a test brings a DEP violation: $500 for an unfiled annual report and $700 for a missing device, up to $1,000 on default.
In This Guide
01
Which Buildings Need a Backflow Preventer
DEP's cross-connection rules require a backflow preventer wherever a building's plumbing could push contaminated water back into the city main. DEP's list includes:
- Roof tanks and other elevated water storage
- In-ground irrigation and pools
- More than one domestic service line, with a device on each
- Large or chemically treated boilers
- Water-cooled equipment and chillers
- Hospitals, medical and dental offices, laundries, car washes, food businesses, and schools
A residential building with a single domestic line may qualify for an exemption, filed with DEP by a PE or RA.
02
RPZ, Double Check, or Air Gap
The device a building needs depends on the degree of hazard, as set out in DEP's cross-connection handbook.
- Hazardous: could cause illness
- ExamplesLaboratories, hospitals, mortuaries, chemical use
- Allowed devicesAir gap or reduced pressure zone (RPZ) assembly
- Aesthetically objectionable: taste, odor, or color
- ExamplesFood-grade dyes, hot water, stagnant fire-line water
- Allowed devicesAir gap, double check valve, or RPZ
- Hazard can't be determined
- ExamplesMixed or unclear uses
- Allowed devicesRPZ
An RPZ has two check valves with a relief valve between them. If either check leaks, the relief valve dumps water through an air gap, which is why an RPZ needs a drain nearby.
03
Installing a New Device
A new device goes through DEP and DOB in this order (DEP FAQ):
- 1
Plan by a PE or RA
The engineer or architect prepares the plan and submits it to DEP on form GEN236. Approved plans are good for two years.
- 2
Install Under a DOB Permit
A licensed master plumber installs the device with a DOB plumbing permit.
- 3
Initial Test Within 30 Days
A certified tester tests the new device, and the report goes to DEP within 30 days of installation.
04
The Annual Test and Report
After that, each device is tested every year, no more than 12 months after the last test. DEP mails a notice when one is due.
- 1
Test by a Certified Tester
The tester must be certified by the NYS Department of Health. Licensed master plumbers can be certified testers too.
- 2
Repair and Retest if It Fails
A licensed master plumber repairs or replaces a failed device, and it's retested, with both results on the report.
- 3
File Form GEN215B
One GEN215B per device, sent to DEP online or by mail to its Cross-Connection Control Unit.
05
Penalties for Missing a Test
Violations are heard at OATH under its water penalty schedule:
- Annual test report not filed
- Penalty$500, or $1,000 on default
- No device installed, or initial test report not filed
- Penalty$700, or $1,000 on default
- Device removed or bypassed without DEP approval
- Penalty$700, or $1,000 on default
DEP does enforce it: in 2025 it issued 5,939 violations for unfiled annual test reports and 1,020 for devices never installed, according to its report to the City Council.
We test, repair, and file for RPZ and double check assemblies across NYC. See our backflow testing service.
06
Common Questions
How often does a backflow preventer need to be tested in NYC?
Every year, no more than 12 months after the previous test, plus after installation and after any repair.
Who can test a backflow preventer in NYC?
A tester certified by the NYS Department of Health. Installation and repairs are done by a licensed master plumber.
What form is used for a NYC backflow test?
Form GEN215B, the Report on Test and Maintenance of Containment Backflow Prevention Assembly, one per device, filed with DEP online or by mail.
What happens if I don't file my backflow test?
DEP issues a violation heard at OATH: $500 for an unfiled annual report, or $1,000 on default. DEP can also shut off water service.
What's the difference between an RPZ and a double check valve?
An RPZ adds a relief valve between its two checks and is required where backflow could make people sick. A double check valve is allowed only where the risk is taste, odor, or color.
Does my building need a backflow preventer?
If it has roof tanks, chillers, a large or treated boiler, irrigation, more than one service line, or a business like a restaurant or medical office, very likely. A PE or RA can confirm it with DEP's risk assessment guide.
Sources
- NYC DEP: Cross Connection Controls
- NYC DEP: Backflow Prevention FAQ
- NYC DEP: Cross-Connection Control Handbook (January 2019)
- NYC DEP: Form GEN215B
- OATH: Water Penalty Schedule (2021 rule)
- NYC DEP: Cross-Connection Report to the City Council (February 25, 2026)
- NYS DOH: Certified Backflow Testers
This guide explains NYC rules in plain terms. It isn't legal advice, and rules and utility procedures change; check the sources above or call us about your building.