Reticulation

The first cause is a retic system that is not giving adequate coverage. Likely reasons are blocked / broken/ misaligned sprinklers, change in pressure or sprinklers that have been replaced and don't match the system. You check retic systems by finding out how many millimetres of water are being applied during each watering time. The pressure is measured by putting aerosol caps around your system and measuring the amount of water in each.

If watering twice a week you need a minimum of 15mm in normal conditions and 20mm during a heat wave. These figures will let you know how long to run each station to get the required amount of water (stations may vary depending on pressure and sprinkler type). Different types of sprinklers put out vastly different amounts of water.

Contrary to public perceptions, there is no time limit to how long each station runs for, as long as you water within your allocated watering day and time. Consideration must be given to drift from prevailing winds. Once you have audited your retic system and it is working satisfactorily you can look at the non wetting properties of your soil (hydrophobia).