Identify a backflow device from the current plan's legend and device schedule, not from one assumed symbol.
Brisbane City Council requires hydraulic plans to define every symbol they use. Plans with testable backflow devices must also schedule the make, type, location, size and serial number.
Is there one standard backflow symbol?
No single remembered shape is safe to apply across every hydraulic drawing. Consultants can use different schematic marks, abbreviations and equipment tags, provided the plan defines them.
The Brisbane hydraulic plan guide requires a legend defining all symbols on the cover sheet or first page. That project-specific legend controls what its marks mean.
A schematic mark is also not a scaled picture of the installed assembly. The actual installation may include isolating valves, test points, a strainer, connecting pipework and a separate identification tag.
Which backflow abbreviations might appear?
| Code | Device or method | What to check |
|---|---|---|
| RPZD | Reduced pressure zone device | Confirm the exact code in the project legend and backflow schedule. |
| DCV | Double check valve | Do not assume it means every product containing two checks. |
| DCDA | Double check detector assembly | Keep it distinct from a standard double check valve. |
| PVB | Pressure type vacuum breaker | Confirm that the drawing uses this exact abbreviation. |
| AG or BT | Air gap or break tank | These are different protection methods and may not appear as an inline valve. |
The Australian Building Codes Board cross-connection handbook distinguishes these device types and abbreviations. It does not make its operating diagrams a universal plan-symbol set.
Brisbane's own backflow table example uses RPZD and DCV. Treat those as verified type codes, then check how the actual project defines and tags them.
How do you verify the mark step by step?
- Check the document: confirm its title, revision and whether it is approved, issued for construction or as-constructed.
- Read the legend: find the exact symbol, abbreviation or equipment tag used on that drawing set.
- Trace the service: follow the connected water line and read nearby flow, service and location notes.
- Find the schedule: match the tag to the testable backflow table and its recorded device type and location.
- Compare the installed record: check the make, model, serial number or council ID without operating the device.
- Resolve conflicts: ask the hydraulic designer, building manager, relevant council or appropriately endorsed plumber when details disagree.
Do not rely on a tender or concept drawing when a later approved or as-constructed revision exists. The revision table and current issue status are part of the identification check.
What information should the device schedule contain?
For a testable device, Brisbane's submitted-plan example records the make, device type, location and reason for installation, size and serial number. As-constructed schedules must be completed with the installed details.
That information separates two similar plan marks at different locations. It also lets the reader compare design intent with the registered and installed device.
Logan City Council's commercial final guidance also uses a backflow table containing make, type, location, size and serial number. Its examples are local documentation guidance, not a statewide symbol library.
How do you match the plan to the physical valve?
Start with the recorded location, then read the manufacturer's label, model and serial or ID number. Do not identify the assembly by brass colour, body shape or apparent number of valves.
Brisbane City Council records testable devices and their locations through its backflow registration and testing process. Form 9 is used for device registration and test reporting.
The record can help confirm identity, but it does not prove the current installation matches an old drawing. Alterations, replacements and revised hydraulic plans must be checked against the latest documents.
Does the symbol tell you which device is required?
No. A plan mark records a design decision; it does not perform the hazard assessment or prove the installation is compliant.
Backflow protection includes several mechanical and non-mechanical methods. Selection depends on the cross-connection hazard, water-service arrangement, operating conditions and applicable approval pathway.
Read our guide to selecting and locating a backflow preventer for that separate decision. The drinking-water backflow guide explains why the protection is needed.
What if the plans are missing or inconsistent?
Do not substitute a device, operate test points or close isolating valves to investigate. A protected service may supply fire, medical, commercial or other critical uses.
Ask the building manager for the current approved and as-constructed drawings, device schedule and latest test record. For Brisbane properties, Council's registration information can help locate a recorded testable device.
An appropriately licensed and backflow-endorsed plumber can compare the installed assembly with the records. Our guide explains who can install or test a Brisbane backflow device.
Keep clear and arrange prompt assessment by an appropriately licensed and backflow-endorsed plumber if a device is damaged, leaking heavily, discharging unexpectedly or appears bypassed. Its appearance still does not establish the fault or safe repair.