A smart water timer which includes a water timer, a receiving unit connected to the water timer, and a moisture sensing unit which is in wireless communication with the receiving unit. The smart water timer can sense when the moisture level in the soil is too moist (based on a user setting) and turn off a water supply to a sprinkler as a result A soil moisture sensing unit is placed in the soil in the area to be watered. The soil moisture sensing unit uses a moisture sensing probe and wirelessly transmits a data signal to the receiver, which is connected to the water timer, indicating whether or not the water timer should be permitted to open a water valve.