You only get once chance to get it right when planting grass seed. Watering the seed is essential. Simply put--without water, the seed will fail to germinate and will die. However, too much water will also prevent the seed from sprouting. The key is to keep grass seed moist at all times. There isn't a magic number of inches of water required weekly. You need to take the environment and climate into account to determine exactly when to water grass seed and for how long.
Pay close attention to the moisture content of grass seed during what's called the pre-sprout. This is right after the seed is dispersed, before it germinates. Moisture is essential during this phase. It can take seed between five and 30 days to sprout. If the weather is cool, it can take even longer.
Insert your finger 2 inches into the ground. Determine whether the soil feels moist. It should not be soggy or dry.
Test the moisture in several places on your lawn, because seeds do not germinate at the same time. They may be buried at varying depths or have a different quality. This will cause some to sprout earlier than others. The soil needs to be consistently moist to make sure all the seeds have a chance to sprout.
Alter the watering requirements based on the location of the seed. Areas that are under shrubs, trees, overhangs or in the shade will not dry out as fast as grass seeds planted in the sun.
Set up a sprinkler in the middle of your lawn. If the spray goes far enough, you can keep it in that spot. If the spray is shorter, you may need to move it around to evenly water the entire yard.
Spray the lawn two to three times daily to keep the grass seed moist. A light spraying will ensure consistent results. Make sure the sprinkler doesn't cause any pooling from leaks or a loose hose.