Backflow test invoices: the serial number and the test report

The water utility sends its yearly reminder: the backflow assemblies at your properties are due for testing. A plumber or sprinkler company does the rounds and sends invoices, one test per assembly, some with a repair line added: “replaced check valve rubber, retested, passed”. Attached is a photo of a test kit, hoses clipped onto the brass test cocks of a valve beside a building. The work may be exactly as billed. But a photo of a test kit shows that someone was standing at an assembly. It doesn’t show which assembly, what the gauge read, or whether anything was repaired. For this job there is a better document than the photo, and in Utah the state publishes the form for it. This piece covers what the photo can show, what the test report records, and the checks. It is not legal advice.

Why the test is billed every year

A backflow assembly keeps water from a building or a sprinkler system from flowing back into the public water supply. Utah’s drinking water rules put the job of policing them on the water system: under R309-105-12, assemblies “shall be inspected and tested at least once a year, by an individual certified for such work”, and “the water system management may require that the customer having the backflow prevention assembly be responsible” for getting it done. That customer is often a property owner. The water system must keep “a service record for each such assembly” and records of the inspections.

That last part is what makes this job checkable. The tester doesn’t only report to you. Under R309-305-8, a certified tester must “report backflow prevention assembly test results to the appropriate public water system within 30 days”. Your water utility may set its own, shorter deadline. So a second copy of the test exists, held by someone with no stake in your invoice.

What the photo can show

• That someone was at an assembly. A test kit with its hoses on the test cocks shows a tester connected to a valve.
• Sometimes which one. If the photo shows the tag or the casting with the serial number, or the building behind it, it ties the visit to an assembly. A close-up of a gauge doesn’t.
• Sometimes when. If the file still carries the camera’s own clock, the date should fall on the visit.

What it can’t

• The result. A test is a series of readings: each check valve, the relief valve, then a final test after any repair. One picture of a needle is one moment of one step.
• That a repair happened. A rebuilt check valve looks like any other from the outside.
• That it came from this property. Backflow assemblies of the same make look alike at every address, and so do test kits.

What the test report records

The Utah Division of Drinking Water publishes a Backflow Assembly Test Report form on its tester page. Utilities and testers may use their own versions, but the state form shows what a complete report holds:

• The assembly: its owner, address and location, the serial number, size, model number and manufacturer, and its type. There is a box for a replaced assembly with a line for the “old serial #”.
• The initial test: the readings for each check valve and the relief valve, before anything is touched.
• Repairs: what was cleaned or replaced, for each part. R309-305-8 requires the tester to “include, on the test report form, any materials or replacement parts used to repair or to perform maintenance”.
• The final test, and whether the initial and final tests each passed or failed.
• Who did it: the technician’s printed name, certification number and phone, with a signature and date for the initial test, the repair and the final test.

The form’s own footer lists its distribution: “Assembly Owner, Tester, and Water Utility”. If you are the owner, you are meant to get a copy.

Line the invoice up against that report. A repair charge should match an entry in the repairs section, with parts listed, and normally an initial test that failed. An invoice that bills a repair on an assembly whose initial test passed, with nothing written under repairs, is worth a phone call. So is a replacement assembly billed without a new serial number and the old one recorded.

Checks before you pay

1. Ask for the completed test report with every test invoice, one per assembly. A photo of a gauge is not a substitute for it.
2. Keep a list of your assemblies by serial number. Each year’s report should show the same serial at the same location, unless a replacement is recorded with the old serial. A serial you have never seen before, at a property where nothing was replaced, is worth asking about.
3. Look up the tester. The Division of Drinking Water lists certified backflow technicians on its public lookup, which the state describes as a way to “check the information and expiration status of a Backflow Technician”. Match the certification number on the report.
4. If something doesn’t add up, ask the water utility whether it received a report for that assembly and that date. It is required to keep records of the tests.
5. Ask for the original photo files, not pictures pasted into an invoice PDF, which have usually lost their camera record. Why, and how to ask for the originals.
6. Drop this year’s photos in with last year’s. The checker marks any two files in the same batch that are the same file, even under different names. A test kit photo reused across properties or years shows up that way. A new photo of a test kit on some other assembly won’t, which is why the serial number and the report matter more than the picture.

Whether someone used AI on the photos

A picture of a test kit on a brass valve is easy to generate now, and some generators write a mark into the file saying so. The checker reads those marks in photos, and the notes some phone editors leave when generative AI was used to alter a photo. A file with no such mark is not proven real. Most fakes and most genuine photos look the same to a file reader once they have been through a chat app or a screenshot. And for this kind of job, even a perfectly genuine photo doesn’t say how the assembly tested.

The limits, stated plainly

• A photo of a test kit shows someone at an assembly. It doesn’t show which one, the readings, or any repair.
• A test report is the tester’s own record. Its value is that it is detailed, signed, tied to a serial number and certification number, and also sent to the water utility, not that anyone else watched the test.
• The rules quoted are Utah Administrative Code R309-105-12 and R309-305-8, read through Cornell LII’s copy, plus the Division of Drinking Water’s tester page and its test report form, all read in October 2026. Other states and individual water utilities set their own rules, deadlines and forms, and we have not covered them, or which assemblies a given utility requires.
• A photo with no camera record is not a fake. Text messages, chat apps and many portals remove the record from genuine photos every day.
• Our checker gives no confidence score and does not judge a picture by looking at it. It reads what is in the file, in your browser, and uploads nothing. A file with no AI marker is not proven real.
• This is not legal advice.

Related: what a contractor’s “after” picture actually proves, and water heater invoices and the data plate.

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