 which can actually, honestly, overwater your grass. Now, a good rule of thumb is to make sure your lawn gets one inch of water a week. Now, smart timers can help. You can pick one up and adjust the water based on rainfall. So whether you use an in-ground sprinkler system or one that uses hoses, you can use timers to control the amount of water that that lawn is receiving, save money, and still have a green lawn.