How to Install Underground Sprinkler Wiring

Introduction

Installing underground sprinkler wiring allows you to automate and control your lawn irrigation system. Having an underground sprinkler system with automated controls can save time and water compared to manual watering with a hose or sprinkler. In this comprehensive guide, I will walk you through the entire process of installing underground sprinkler wiring step-by-step.

Things You Will Need

Before starting the installation, make sure you have all the necessary materials and tools:

Wire - Use 14-gauge or 12-gauge direct burial sprinkler wire. You need a wire for each zone in your system.
Wire connectors - To join the wires together. Waterproof connectors are recommended for underground use.
Conduit - Use PVC conduit to protect wires running under driveways, sidewalks, etc.
Trencher or shovel - To dig the trench for the wiring. Rent a trencher for large areas.
PVC primers and cement - For gluing conduit connections.
Electrical tape - To waterproof connections.
Wire puller - Makes it easier to pull wires through conduit.
Mulch, sand, or soil - To backfill the trench after laying the wires.

Planning the Wiring Layout

Careful planning is crucial before you start digging. Here are some steps to plan out your wiring:

Mark where each sprinkler head will go with flags or spray paint. Group heads into zones based on area.
Decide where to place the controller. Garage, shed, or side of house are common locations.
Lay out the wiring path from each head to the controller. Wires typically run alongside buildings or fences.
Mark where you will need conduit - under driveways, sidewalks, etc.
Contact utility companies to mark any underground lines. Avoid digging near marked lines.

Planning a logical layout will make installing much easier.

Digging the Trench

Now it's time to start digging. Here are some tips for digging the wire trench:

Dig trenches 6-12 inches deep. Deeper than 12 inches provides extra protection.
Trench width should be 2-6 inches wide. Make wider trenches where multiple wires run together.
Follow your planned layout using spray paint or flour to mark trench lines.
Use a trencher for large open areas. For small areas, a shovel usually works fine.
Place PVC conduit in trenches that go under hardscapes before backfilling.
Call 811 to mark utility lines before you dig! Avoid digging near marked lines.

Take care when digging trenches - make sure to call 811 before you dig to avoid hitting any utility lines!

Running Wires Through the Trench

Here is the process for running your sprinkler wires through the open trench:

Start at the controller location. Leave 2-3 feet of extra wire before trench.
Lay wires end-to-end through the trench. Do not splice underground.
Use a wire puller to pull wires through any conduit.
Make gradual sweeps when changing wire direction. No sharp turns.
Leave an extra 2-3 feet of wire at the end before digging the head.
Label wires indicating the zone at the controller end. Use tape or tags.
Waterproof all connections using electrical tape.

Running the wire cleanly through the trench will prevent damage and signal issues.

Connecting Wires to Sprinkler Heads

Connecting the wires to the sprinkler heads involves just a few simple steps:

At each head, leave a 6 inch wire tail above ground after trenching.
Strip away insulation from the ends of the wires.
Connect zone wires to the appropriate terminals on the sprinkler head.
Waterproof connections using electrical splice caps.
Tuck extra wire back into the trench carefully to avoid damage.
Test wiring before backfilling trench. Confirm each head has power.

With the wires connected at each head, you can test the system before burying the wires.

Backfilling and Finishing Touches

The final steps are backfilling the trenches and completing the system:

Partially backfill trenches to cover wires, then test system again before finishing.
Complete backfilling with original dirt or use sand/gravel for better drainage.
Compact soil lightly with a tamper tool. Do not crush wires!
At controller, label wires and connect to proper zone terminals.
Program the irrigation controller with zone run times.
Turn on water supply and pressurize system. Check for leaks.
Run each zone to confirm proper operation and make any adjustments.

With that, your underground sprinkler wiring project is now complete! The system is ready to keep your lawn healthy and green all year. Let me know if you have any other questions!