How to Connect a Moisture Sensor to a Water Timer

What You'll Need
Moisture sensor
Irrigation controller unit with timer
Thin gauge outdoor electrical wire
Wire nuts
Wire cutters
Wire strippers
PVC pipe and couplers
PVC glue and primer

If you want to make sure your garden gets the water it needs but isn't exposed to over-watering, you can connect a moisture sensor to the control unit timer on your irrigation system to allow watering when the soil is dry and to prevent the device from turning on water when the soil is already wet. Connecting a moisture sensor to the timer control unit is easier than you think, and this simple how to guide will show you everything you need to know.

Step 1 - Choose Location and Dig Trench

First, choose a location for the moisture sensor to be installed. Then, use a shovel to dig a trench that is about 4 to 6 inches deep from the location where the sensor will be installed to the timer control unit.

Step 2 - Cut and Lay Pipe 

Lay out the thin gauge PVC pipe in the trench. If you have to cut a piece, use a hacksaw and then sand the edges of the pipe with sandpaper. Clean the pipe ends and couplers with PVC primer and then secure the pipe ends together with PVC glue.

Step 3 - Run Wiring

Have someone help you fish the electrical wire for the connection through the completed PVC pipe assembly. Make sure that you have a few inches of extra wire on each end of the pipe so that you have plenty to work with when connecting the moisture sensor and timer control unit.

Step 4 - Connect and Install Moisture Sensor

Connect the black and white thin gauge electrical wires to the appropriate terminal leads on the moisture sensor. Then, use the included stake to plant the moisture sensor at the appropriate level in the soil. Refer to the instructions that came with the sensor on how deep to bury it.

Step 5 - Connect Wiring at Controller Unit

Connect the electrical wire to the terminal leads on the controller unit. In most cases, you simply need to screw the wiring to the built in terminals for a moisture or rain sensor.

Step 6 - Set Up Rain Sensor on Controller

Refer to the operating instructions that came with your timer controller unit for setting up the sensitivity level for the rain or moisture sensor. Then, adjust the sensor accordingly.

Step 7 - Bury Pipe and Replace Grass

Once all of your connections have been made and secured with wire nuts, make sure that the moisture sensor and controller unit are in their final installation positions and begin burying the PVC pipe. When burying the pipe, try to pack the soil as tight as possible. Once you have the pipe covered, replace the grass that you removed earlier with a shovel.

Step 8 - Test the Installation

In order to test the moisture sensor, take a cup of water and pour it in the area where the sensor is located. Then, turn on the controller unit that controls your irrigation system. If the moisture sensor is working properly, water should not be directed to the area where the sensor is installed.