Backflow is a dangerous condition where contaminated water from your irrigation system flows back into the potable water supply. It can occur through back-siphonage (a drop in supply pressure) or back-pressure (irrigation system pressure exceeds supply pressure). In most jurisdictions, installing a backflow preventer is a legal requirement.

Types of backflow preventers

1. Atmospheric Vacuum Breaker (AVB)

The simplest type. Uses an air gap to break the vacuum when pressure drops. Key limitations:

  • Must be installed 150 mm (6") above the highest sprinkler head
  • No downstream shutoff valves allowed
  • Protects against back-siphonage only — not back-pressure

Price: €15–30 ($16–33). Suitable for small residential systems without chemical injection.

2. Pressure Vacuum Breaker (PVB)

Similar to AVB but includes a spring-loaded check valve that also handles back-pressure.

  • Must be installed 300 mm (12") above the highest sprinkler head
  • Requires annual testing
  • The most common choice for residential irrigation in the US

Price: €40–80 ($44–88). Best price-to-protection ratio for residential systems.

3. Double Check Valve (DCV)

Two inline check valves with test ports between them.

  • Can be installed below grade — no height requirement above sprinkler heads
  • Suitable for commercial applications without chemical injection
  • Requires annual testing by a certified technician

Price: €60–120 ($66–132). Ideal when above-ground installation is not possible.

4. Reduced Pressure Zone (RPZ)

The highest level of protection. Features a reduced pressure zone between two check valves and a relief valve.

  • Mandatory for chemigation/fertigation (fertilizer injection through irrigation)
  • Automatically discharges water when backflow pressure differential is detected
  • Requires drainage below the device (discharges 15–30 L/min when activated)
  • Annual testing is mandatory

Price: €150–400 ($165–440). Required for chemical treatment and high contamination risk.

How to choose the right type

  • Residential lawn, no chemicals → PVB (best price-to-protection ratio)
  • Fertigation or chemical injection → RPZ (mandatory)
  • Below-grade installation needed → DCV
  • Simple small system → AVB (lowest cost)

Installation requirements

  1. Height: AVB — 150 mm (6"), PVB — 300 mm (12") above the highest sprinkler head
  2. Drainage: RPZ requires drainage provisions (discharges water when activated)
  3. Testing: RPZ and DCV — annual inspection by a certified backflow tester
  4. Frost protection: insulate or drain for winter (especially RPZ with water in the body)

Local codes and standards

  • US: UPC/IPC require backflow prevention on all irrigation connections
  • EU: EN 1717 classifies risk levels and corresponding preventer types
  • Australia: AS/NZS 3500 — mandatory backflow prevention

SmartPluvia and backflow prevention

The valve catalog in SmartPluvia includes backflow preventers. The BOM generator automatically adds the appropriate type based on your system configuration. Open the planner, add your valves — and the system selects the right preventer for you.