Reading flow rate measurements

Once your irrigation schedule has been determined, read the flow meter to confirm that the system is applying the amount of water it was designed to apply.

Because of the large number of variables at play in an irrigation system, the measured application rate cannot be expected to be exactly the same as the predicted rate. What you are looking for are large differences – either sudden or gradual.

A large difference indicates either a problem in your calculations or a physical system problem such as a broken or clogged line. Measure and record flow meter readings for the new system, and on a regular basis so that you can observe any flow rate variations that may occur.

Flow rate variances, and their potential problems are listed below.


Flow rate variance diagnoses


Possible Problem

Gradual decrease in flow rate

  • Emitter clogging
  • Could indicate pump wear or filter clogging – check pressures

Sudden decrease in flow rate

  • Stuck or clogged control valve
  • Other flow restriction – check pressures
  • Water supply failure – check pressures

Gradual increase in flow rate

  • Incremental damage to laterals from insects or other pests

Sudden increase in flow rate

  • Damaged or broken lateral
  • Damaged or broken submain
  • Damaged or broken mainline
  • Pressure regulator failure

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