How do I read a backflow test report and its numbers?

The Phoenix report is one page. It identifies the assembly and the site, records the readings in psid, lists any repairs, and ends with the tester's pass or fail, signature and numbers. Psid means pounds per square inch, differential. It is the pressure difference across a valve inside the assembly, read on the tester's gauge. So a reading is not the water pressure in your pipes. It is how much pressure difference a valve can hold.

The city's report form (TRT 00337) has these parts:

• Site and assembly details. Water purveyor, meter number, permit number, and the assembly's manufacturer, size, model and serial number.
• Type of assembly. The tester marks SVB, PVB, DC, RP or Other.
• Line pressure and back pressure. The instructions say to give the line pressure at the time of the test. The form also asks whether back pressure is present.
• Initial test. The readings, in psid, for the parts that apply to your assembly type.
• Repairs. What was cleaned or replaced, such as a rubber kit, disc, spring or guide. The instructions say part numbers must be listed.
• Final test. The readings again, after any repair.
• Sign-off. Pass or fail, the tester's certification number, and the test kit serial number. If the assembly failed first, the form also has the dates it failed, was repaired and passed.

The form has a certification line above the tester's details: THIS REPORT IS CERTIFIED TO BE TRUE. For a box-by-box walk through the top of the form, see how to hire a backflow tester and what is on the report. This page picks up at the readings.

Each assembly type has its own set of readings, and you only need to read the ones for your type. The instructions say this directly: different test procedures require different information. To read yours, first find the type box, then look only at the readings for that type.

One caution about pass limits. The Phoenix form has blanks for readings, but it does not print the limits. Phoenix's code points testers to Section 9 of the USC Foundation's Manual of Cross-Connection Control for the procedure. The manual is copyrighted, so we did not use it. Instead, the limits below come from the Los Angeles County Department of Public Health testing manual, which references the USC Foundation's Tenth Edition manual and publishes its requirements openly. Phoenix's code names the Ninth Edition, so a tester may cite a different edition than the one below. Treat these as the usual pattern and let your tester and city confirm.

### How do I read a reduced pressure (RP) assembly?

An RP assembly has two check valves with a relief valve between them. Its report has three main entries:

• Check valve 1. Marked closed tight yes or no, with a psid reading.
• Differential pressure relief valve. An opened-at reading in psid, or a mark that it did not open.
• Check valve 2. Marked closed tight yes or no.

The Los Angeles County manual says the relief valve must operate to keep the zone between the check valves at least 2.0 psi below the supply pressure. So an opened-at reading of 2.0 psid or higher is the usual benchmark for the relief valve. It says check valve 2 must be tight against reverse flow under all pressure differentials. For check valve 1, it says the static pressure drop should be at least 3 psi greater than the relief valve opening. It then adds that the 3 psi buffer is a manufacturer's specification, and that a result under 3 psi would not automatically fail a device as long as the check valve is holding tight.

Here is a made-up example. Say a report shows check valve 1 closed tight at 7.0 psid, the relief valve opened at 3.0 psid, and check valve 2 closed tight. Both checks hold and the relief valve opens above 2.0. That reads like a pass.

A relief valve that will not open, or one that keeps discharging, tells a different story. If yours drips or spits, why an RPZ valve spits water explains the usual causes.

### How do I read a double check (DC) assembly?

A DC assembly has two check valves and no relief valve. Its report has two entries, one for each check valve, with closed tight yes or no and a psid reading for each.

The Los Angeles County manual requires each check valve to hold water pressure at 1.0 psid or greater in the direction of flow. If a valve holds less than 1.0 psid, or the form says it leaked, that check valve fails. For how a DC differs from an RP, see RPZ vs double check backflow assemblies.

### How do I read a pressure vacuum breaker (PVB) or spill-resistant vacuum breaker (SVB)?

These are the assemblies you often see on irrigation lines. The Phoenix form uses the same two entries for both:

• Air inlet opened at. A psid reading for the point where the air inlet valve opens.
• Check valve held at. A psid reading for what the check valve holds, plus a leaked yes or no.

The Los Angeles County manual says the air inlet must open when the water pressure in the body is at least 1 psi above atmospheric pressure, and must be fully open once the body has drained. It also requires the check valve to hold 1.0 psid or greater in the direction of flow. We did not find a separate published limit for the SVB in the sources we reviewed, so ask your tester which procedure they used for one.

### What if a number looks different from what I expected?

A single odd number is a reason to ask a question, not to assume a failure. The Los Angeles County manual notes that leaking shutoff valves can prevent a test from being made, and that they must be repaired. It also says a tester has to tell apart several causes when a relief valve discharges during a test. This is why the report is signed by the person who was there. If a number seems off, ask the tester what they saw and how they ruled out a shutoff valve leak.

A pass means the assembly worked as designed on the day of the test, and it can stay in service. Arizona's backflow rule, R18-4-215, says an assembly shall not be placed in service unless it has been tested and is functioning as designed. It also says an assembly found defective shall be repaired or replaced. Testing is due at least annually, and again after installation, relocation or repair.

In Phoenix, the customer submits the results. The city's code, as quoted in its guidance document, says that if a test shows the assembly to be defective or in unsatisfactory operating condition, the customer shall make repairs or replacement to the satisfaction of the Planning and Development Director. Read on the form, that means a fail is not the end of the story. A repaired assembly gets a final test, and the final test readings are what count. What to do after a failed test covers each step and each city's deadline.

A pass also does not mean the report is acceptable. Phoenix's instructions say inaccurate or incomplete reports will not be accepted, and that the owner will be told the backflow certification for the assembly is not acceptable.

Read the report top to bottom before it goes to the city, and look for blank boxes, numbers that do not match the marks beside them, and missing signatures. Use this list:

1. 1Type box. It matches the assembly on your site.
2. 2Serial number. It matches the tag on the assembly.
3. 3Reading boxes. Every box for your assembly type has a number or a mark, not a blank.
4. 4Closed tight and leaked marks. They agree with the psid numbers next to them. A check valve marked closed tight with a very low reading deserves a question.
5. 5Repair section. If parts were replaced, part numbers are in the comments.
6. 6Final test. A failed first test has final readings and a pass date.
7. 7Sign-off. The report shows a pass or fail mark, a signature, the certification number and the test kit serial number.

The certification number is the one to look up. What tester certification involves explains what it means, and where to send backflow test reports in Phoenix covers filing. If you do not know where your assembly sits, start with where is my backflow preventer.

A certified tester reads the gauge and signs the report. A licensed plumber steps in for what the report turns up, such as a leaking pipe near the assembly, a failed shutoff valve, or a drain that has to carry relief valve discharge. Whether an RPZ valve needs an air gap and drain is a common question after a report.

HQ Plumbing & Air is licensed and insured, and we give free estimates with upfront pricing. We offer 24/7 emergency service when a line fails or water is spraying. For the commercial side of that, see commercial plumbing.