How to flush

First – pressurize the system.

Mainline Flushing


  • Submain flush valve
  • Lateral flush valves



  • Mainline flush valve
Submains Flushing


  • Mainline flush valve
  • Lateral flush valves



  • Submain flush valve
Drip laterals Flushing


  • Main flush valve
  • Submain flush valve
  • Most of the lateral flush valves (see below)



  • Open a small portion of laterals at a time (generally
    up to 25% of the block at one time). This is to ensure
    adequate flushing velocity while maintaining the
    required flow and pressure of the entire system.
  • Once they are flushed, close the laterals in
    consecutive order


An easy method to check your water velocity

A bucket can be used at the end of a lateral to measure if the flow rate is adequate.

Pipe size (ID) Water volume in 1 minute
for flushing velocity 0.3 m/s (1.0 ft/sec)
Water volume in 1 minute
for flushing velocity 0.5 m/s (1.5 ft/sec)
13.8 mm (0.540 in) 2.7 liters (0.71 gal) 4.5 liters (1.2 gal)
17.4 mm (0.680 in) 4.3 liters (1.1 gal) 7.1 liters (1.9 gal)
22.1 mm (0.860 in) 6.9 liters (1.8 gal) 11.5 liters (3.0 gal)


If the volume collected in a minute is below the amount as per the table above, the flushing velocity is insufficient. In this case:

  • Try opening fewer laterals at a time.

  • If this still does not work, you can change hydraulic valves from “auto” to “open” in order to bypass the pressure regulating function of the valve. However, caution is advised to not exceed pressures that the system can handle.


When is the flushing complete?

In particular for the laterals, there will be four stages.

1 Dirty water
(contaminants at the line end)

2 Clean water
(don’t stop yet)

3 Dirty water again
(the contaminants along the line)

4 Clean water


Self-flushing line ends

These are small valves that are “normally open”’ (NO), but they close when the system reaches a certain pressure. This creates a short flush at the beginning and end of each irrigation system.

Self-flushing line ends help clean the system, in particular the line ends, but they do not provide a high velocity flush.

Normal flushing is still required.

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