Set up two to three sprinklers over your yard. Make sure that your yard's entire surface gets watered when the sprinklers are turned on. Try not to overlap the sprinkler's spray patterns; this can cause muddy areas.
Turn on the sprinklers two to three times per day for 20 to 30 minutes each time. Do not allow the hydroseed mixture to dry out. The hydroseed requires more water on warmer and windy days than on cooler and calmer days. Continue this watering regimen for the first two weeks.
Starting the third week, water the hydroseed once per day for 20 to 30 minutes each day. The best watering time is in the morning. Continue this watering regimen until you mow the grass for the first time. The grass is safe to mow once most areas are at least 3 inches tall.