Tech Self Help Articles » Nozzle Circuit » Low Nozzle Flow Rate Warning

Low Nozzle Flow Rate Warning

iMist has identified that the last AFR (average flow rate) of the nozzle circuit is less than 30 ml/min.

If a nozzle circuit is installed correctly, and the nozzles are not fouled, the average flow rate should be in the 40 – 50 ml/minute range.  Below about 30 ml/min, the mist is not projected well.  It doesn’t drift around the property, and the systems lose effectiveness.  Check out these photos comparing the mist pattern and density at different flow rate.

Potential Cause:
  • The nozzles are clogged.
  • The pump is worn and failing:
    • Rotor blades are scored and the pump isn’t producing enough pressure to achieve normal flow.
    • In drum units, when the volume in the drum is low, rather than misting, the pump is using some of the mist cycle to prime itself.
  • The internal bypass on the pump is set too low
  • The nozzle count in the controller is higher than the number of nozzles actually installed.

Look at the level/flow rate chart on the Operations tab on

If the flow rate line shows a gradual decline, the probable cause is clogged nozzles.  You can restore the flow rate by replacing the nozzle tips with new or cleaned/rebuilt nozzle tips.  See Cleaning and Rebuilding Slimline Nozzle Tips.

Install a nozzle circuit filter to prevent it from happening again.  See our Nozzle Circuit Filter Video.


If the flow rate shows a more precipitous decline, the probable cause is a worn/failing pump and you’ll need to replace the pump.