Utility data / field results
A public water system's state filing recorded 844 double check assemblies installed, 716 tested, and 73 failed, with every failed assembly repaired, retested, and returned to passing. The lesson for property owners is that annual testing catches quiet failures while they are still fixable.
Primary keyword: annual backflow testing importance
Key Takeaways
Public water systems file annual cross-connection reports with their state, and those filings are one of the few places you can see backflow prevention working at scale. Perrydale Domestic Water Association's filing with Oregon is a clear example.
As reported in that filing, the system had 844 double check assemblies installed. Of those, 716 were tested during the reporting period, 721 are recorded as passing, and 73 are recorded as failing. The filing also states that all of the failed assemblies were repaired, retested, and passed.
A double check assembly is a common backflow preventer for lower-hazard connections, such as many irrigation and fire lines. It uses two independent check valves so that if one fails, the other still blocks reverse flow. The point of testing it every year is simple: a check valve can wear, foul, or stick without anyone noticing, because nothing looks wrong until the day water tries to flow backward.
The filing does not say whether these assemblies showed visible symptoms before testing. What it does establish is that certified field testing identified 73 failed results and that the repair-and-retest process returned those assemblies to passing condition.
It is tempting to divide 73 failures by the number tested and publish a percentage. That would be a mistake, and the filing itself tells you why.
The report states that every failed assembly was repaired, retested, and passed. That means the pass count includes assemblies that were retested after repair, not just devices that passed on a first look. It shows up in the arithmetic: the recorded passes (721) plus the recorded failures (73) add up to more than the number of assemblies tested (716). A clean, first-test-only tally could not do that.
So the honest way to read Perrydale's numbers is to report them exactly as recorded and resist turning them into a rate. We do not know from the filing how many devices failed on the very first test versus how many results reflect the repair-and-retest cycle, and the pass figure is not a first-test figure. Presenting a percentage would imply a precision the data does not contain.
What the values do support is the thing that matters for a property owner: a large group of protective devices was checked, dozens were caught not doing their job, and every one of those was driven back to a passing condition. That is annual testing functioning as designed.
Backflow preventers are quiet parts of a plumbing system. Under normal pressure, a worn check valve and a perfect one behave identically. The difference only appears when supply pressure drops, during a main break, a hydrant flush, or a sudden spike in demand, and water tries to reverse direction. At that moment, a failed assembly is an open path between a non-potable source and the drinking supply.
Annual testing exists precisely because you cannot see this coming from the outside. A certified tester isolates the assembly, applies gauges to its test cocks, and confirms each check valve holds against reverse flow. Either it holds or it does not. Perrydale's 73 failures are 73 devices that would have looked fine to any building occupant right up until they were needed.
The second half of the lesson is the repair loop. A failed test is not the end of the story; it is the start of corrective work. In the Perrydale filing, every failed assembly was repaired and retested until it passed. For a commercial building or HOA, that same sequence, test, repair, retest, document, is what converts a yearly obligation into real protection. Skipping the retest, or letting a failed device sit, leaves the gap open even though the paperwork trail has started.
Perrydale is a public water system, but the operating habit translates directly to a commercial property, HOA, or managed portfolio in Southern California. Use this checklist to keep your own assemblies from becoming a silent version of those 73.
Common questions from commercial and HOA property owners about failed assemblies and annual testing.
Not necessarily. Many failures are repairable. In the Perrydale filing, every failed double check assembly was repaired, retested, and passed. A certified tester determines whether cleaning or a repair kit restores the assembly or whether it has reached the point of replacement. Either way, the device must be retested and confirmed passing before the compliance loop is closed.
Because the filing records that failed assemblies were repaired and retested, the recorded pass count includes those retested devices, not first-test results only. That is why the reported passes plus failures add up to more than the number tested. The numbers are accurate as recorded, but they are not structured as a first-test tally, so a simple percentage would misrepresent them.
California's April 2026 Cross-Connection Control Policy Handbook requires backflow prevention assemblies to be field tested at least annually. A public water system, the State Water Board, or a local health agency may require more frequent testing for higher-risk premises or assemblies at increased risk of failure.
Double check assemblies are typically used on lower-hazard cross-connections, such as many irrigation systems and fire suppression lines that do not contain additives. Higher-hazard connections, where a health risk is present, generally require a reduced pressure principle assembly instead. Matching the assembly to the hazard is part of a proper cross-connection survey.
