Backflow Preventer
A backflow preventer stops irrigation water from flowing back into the potable water supply. It is a regulatory requirement in most jurisdictions and must be the first component after the water source on the supply pipe.
Backflow PreventerThe Backflow object places a dedicated backflow preventer symbol on your irrigation supply line, immediately downstream of the water source. In the Inspector you record the Type (Air Gap, Vacuum Breaker, Double Check, Reduced Pressure, or Custom) and the Size (mm), so the plan communicates exactly which device the installer must fit. Use it wherever local codes require backflow protection at the irrigation supply entry.
Set the device type in the Inspector
With the backflow preventer selected, open the Inspector and set the device type: 'double-check' (DC — two independent check valves, suitable for low-hazard residential use in many jurisdictions), 'pressure-vacuum-breaker' (PVB — atmospheric break, suitable for above-ground installation), or 'reduced-pressure-zone' (RPZ — highest protection level, often required for systems that use fertilizer injection). Check local plumbing code for the required device type.
Connect with supply pipes
Use the Draw Pipe tool to draw a supply pipe from the water source to the backflow preventer inlet, and from the outlet forward to the pressure regulator or filter. The backflow preventer symbol shows inlet and outlet directions — ensure the pipe flows in the correct direction through the device.
Annotate with test access note
Use the Annotate tool to add a note near the backflow preventer indicating that the device requires annual testing (required by most local codes for RPZ and DC assemblies). Note any access requirements — for example, 'Provide 300 mm clearance on all sides for testing kit connection.' This helps the client understand ongoing compliance obligations.
Set the device type
Select the placed device to open its Inspector. In the Backflow Preventer section, set the Type to Air Gap, Vacuum Breaker, Double Check, Reduced Pressure, or Custom to match the device required by local code.
Set the size
Enter the device Size (mm) in the same section so the specification on the plan matches the supply line bore and the device the installer must source.
Connect the supply pipe through the device
Place a Pipe from the Distribution section and route the supply line from the water source, past the backflow preventer, and onward to the zone valves so the assembly sequence reads clearly on the plan.
Place the backflow preventer, filter, and pressure regulator in order along the supply run — backflow first — so the head assembly sequence is unambiguous to the installer.
The Water tab is a schematic planning tool and does not simulate real-world pressure or flow. The device type and size you record are design specifications for the installer — they do not drive hydraulic calculations.
Backflow prevention requirements vary by jurisdiction and device type (reduced-pressure, double-check, vacuum breaker, air gap). Always confirm which device type is required by local plumbing code before specifying it.
Frequently Asked Questions
Is there a dedicated backflow preventer object?
Yes. The Backflow object lives in the Water tab under Sources & Supply. Place it on the supply line just downstream of the water source and set its type and size in the Inspector.
Where should I place the backflow preventer?
Immediately downstream of the water source and upstream of any zone valves, so the device protects the entire irrigation system from the supply side.
What type options are available?
Air Gap, Vacuum Breaker, Double Check, Reduced Pressure, and Custom. Choose the type required by your local plumbing code.
How do I show the head-assembly sequence (backflow, filter, regulator)?
Place each dedicated object in order along the supply pipe run: Backflow closest to the source, then Filter, then Regulator. Routing the pipe through each one makes the sequence visually clear.
Will the backflow preventer appear on the exported PDF plan?
Yes. Placed water objects appear in plan exports and printouts, so the backflow requirement is visible to the installer and any authority reviewing the documentation.