What is backflow prevention and does my home need it?

NationwideReviewed October 2026

Backflow is water flowing the wrong way, pulling dirty water from a hose, irrigation system, tank or other source back into clean drinking water lines when pressure drops. Devices that stop it range from a simple hose-bibb vacuum breaker on an outdoor faucet to double check valves and reduced pressure (RPZ) assemblies for higher hazards, and an air gap is the most reliable method. The EPA lists irrigation systems, auxiliary wells and rainwater supplies tied into potable lines as common household risks. In Texas, a home with an irrigation system or a second water source connected to city water will usually need an approved assembly, tested by a licensed tester.

Check your local rule. This varies by state, county or city. Your permitting office has the final word; the official lookup pages below show you who that is.

Sources

Find the rule for your area

Official pages from the agencies and code bodies that set these rules.

Want help planning your site?

We can walk you through what your land needs before your home ships.

Call 800-259-1745

General information, written in our own words from the sources listed with each answer. It is not legal, engineering, tax or financial advice. Rules change and differ by state, county and city, so confirm with the office that issues your permit before you build. Last reviewed October 2026.