It is important to know when to water rather than just watering because you think a lawn needs watering. There are a few basic tests you can do to know if your lawn needs irrigation. Look for leaf rolling and curling and the slightly blue/purple tinge which comes when grass is being starved of moisture. Also, try the foot print test. Stepping on a healthy lawn should see it spring back into position quickly but if your lawn is slow to react then it’s time to add more water.