Backflow Rules
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Guide

How backflow testing works

Why your water utility asks for a test, what gets tested, and what happens between the notice and the filed report. The numbers come from the 29 utilities on this site; the device facts come from the U.S. EPA.

What backflow is

Water is supposed to flow one way: from the utility's mains into your property. Backflow is water flowing the other way, from a property back into the public pipes. It can happen when pressure in the main drops, for example during a main break or heavy firefighting, and pulls water back out of a building (backsiphonage), or when a pump or boiler on the property pushes water back in (backpressure).

The risky connections are ordinary ones: lawn sprinkler systems, fire sprinkler lines, boilers, wells and business equipment tied into the drinking water supply. A 2010 Water Research Foundation study cited by the EPA found that about 5% of homes had a backflow event of a gallon or more each year.

Sources: EPA Cross-Connection Control Manual (2003), EPA fact sheet on cross-connection control (2021)

The assemblies that get tested

A backflow assembly is a set of spring-loaded valves with small test ports, so a tester can check each valve without removing it.

Reduced pressure assembly (RP, RPZ)
Two check valves with a relief valve between them that dumps water outside if the first check leaks. Used for high hazards, such as chemicals or a second water source. Water spilling from it means the relief valve has opened.
Double check valve assembly (DC, DCVA)
Two check valves in one body, with test ports and two shut-off valves. Used for lower hazards and on many fire sprinkler lines. The test shows whether either check is stuck or fouled by debris.
Pressure vacuum breaker (PVB)
The common lawn sprinkler device: a spring-loaded valve that lets air in when supply pressure drops. It stops backsiphonage but not backpressure, so it must sit higher than the sprinkler piping it protects.
Spill-resistant vacuum breaker (SVB)
A newer version of the pressure vacuum breaker, built not to spill water when it opens.
Detector assemblies (RPDA, DCDA)
Fire-line versions of the RP and DC with a small bypass meter that shows water use on a line that should sit idle.

An atmospheric vacuum breaker (the simple kind on many old sprinkler valves) has no test ports and is not tested; some utilities no longer accept it.

Source: EPA Cross-Connection Control Manual, chapter 4

The yearly cycle, step by step

  1. 1. The notice. Your utility sends a reminder when the test comes due, and more letters if no report arrives. Of the 29 utilities here, 23 require a yearly test of lawn sprinkler assemblies (Aurora, Colorado Springs, Denver, Boise, Meridian, Nampa, Twin Falls, Beaverton, Bend, Eugene, Gresham, Hillsboro, Portland, Salem, Killeen, San Antonio, Bellevue, Kent, Renton, Seattle, Spokane, Tacoma and Vancouver). 23 also require tests on fire sprinkler lines.
  2. 2. Hire a tester. The tester must hold a certification the utility accepts. 19 of the 29 keep their own list of approved testers (Colorado Springs, Meridian, Nampa, Twin Falls, Eugene, Gresham, Arlington, Austin, Dallas, Fort Worth, Houston, Killeen, San Antonio, Bellevue, Kent, Renton, Spokane, Tacoma and Vancouver). 8 send you to a state lookup instead (Boise, Idaho Falls, Beaverton, Bend, Hillsboro, Portland, Salem and Seattle). Testers set their own prices, so ask for a quote; we don't list prices because they vary by company and assembly.
  3. 3. The test. The tester connects a calibrated gauge to the test ports and checks that each valve holds and the relief valve opens when it should.
  4. 4. The report. At 22 of the 29 utilities the tester files the report for you. Online systems in use: SpryBackflow, SwiftComply, Backflow Prevention Portal, VEPO CrossConnex, EcosConnect, Envirotrax, WEIRS, Vepo (Envirotrax), BSI Online, Backflow Assembly Testing Portal, iBackflow, SAMS Tester Portal and SAMS. Filing fees run $15 to $37.93 where a utility lists one.
  5. 5. If it fails, or nobody tests. A failed assembly is repaired or replaced and tested again by a set deadline (Aurora, Colorado Springs, Denver, Boise, Idaho Falls, Meridian, Nampa, Twin Falls, Beaverton, Bend, Eugene, Gresham, Hillsboro, Salem, Arlington, Austin, Dallas, Fort Worth, Houston, San Antonio, Bellevue, Kent, Renton, Spokane, Tacoma and Vancouver publish theirs). Missing the deadline brings more notices, and 26 of the 29 utilities here say they can shut off water service in the end.

Find your utility's rules

Deadlines, fees and tester rules differ from one utility to the next, even between neighbors. Your notice names your utility.

Look up your utility