How to Bury Underground Cable
We break down four options for underground wiring. Here's what you need to know.
IntroductionRunning electric power to a garage or garden pond? Learn about code requirements and different options for depth of trench, conduit material and type of electrical wire.
- 4-in-1 screwdriver
- Adjustable wrench
- Corded drill
- Electric wire with W (waterproof) designation
- Metal or plastic conduit and fittings
- Service entrance ell
Video: Replacing a 3-Way Switch
Installing an Underground Power Line
If you’re considering running a power line underground through your yard, you have four options. Your choice depends on how much power you want. It also depends on your soil type. If it’s sandy and easy to dig, save money by digging deep (you won’t need to use metal conduit). If it’s rocky or clay, keep your digging to a minimum.
Whichever method you choose, be sure to include a service entrance ell, which has a removable cover to give you access to the inside wires above ground level. And get a permit and talk to your inspector about local codes before starting.
Project step-by-step (5)
Electrical Cable Depth Options
- Decide how much digging you're prepared to do, which determines the type of wire you need to use.
- Underground cable for running electrical power to a remote location can be installed at different depths, depending on the type of conduit and type of wire used.
- For a 6-in.-deep trench, use galvanized rigid metal electrical conduit with individual conductors inside.
- For a 12-in.-deep trench, you can direct-bury GFCI-protected underground feeder cable with a short length of PVC conduit at the house.
- At 18 inches, you can use THWN-2 conductors inside a continuous length of PVC conduit, which protects the wire all the way through the trench to the house.
- At 24 inches you can bury underground feeder cable, using PVC conduit to 18 inches below ground only where the wire comes up.
Bury in the Ground: Dig Six Inches
- At 6 in.-deep, use galvanized metal rigid electrical conduit (1/2-in. dia. is large enough for the water feature) and run individual conductors inside.
- Pro tip: The conductors need to be waterproof, so look for a “W” on the label, as in THWN-2.
- This method lets you run any size circuit.
- The downside is the cost — 1/2-in. metal conduit is more than a dollar a foot.
- Pro tip: If you have soil that's tough to dig, or you only need to run the cable a short distance, go this route to minimize digging.
Bury in the Ground: Dig 12 inches
- At 12-in.-deep, use direct-bury UF-B (underground feeder) cable, provided it meets three criteria:
- It has GFCI protection before it enters the ground;
- Is limited to 120 volts (enough for your fountain);
- Is protected by no more than a 20-amp fuse or breaker.
- Pro tip: We recommend this for your situation — it's only one foot deep and you don't have to put the cable inside expensive conduit.
- This is the best choice if you only need to power your water feature.
Bury in the Ground: Dig 18 inches
- At 18 in.-deep, run THWN-2 conductors inside PVC conduit.
- Pro tip: This method lets you run any size circuit, so it's a good idea if you want to run electricity to other items besides your water feature.
Bury in the Ground: Dig 24 inches
- At 24-in.-deep, run direct-bury UF-B wire cable.
- There's one restriction: It needs a conduit where the cable is exposed on the outside of the house and to 18 inches below the ground.
- Burying the cable 24 inches requires more digging, so this method only makes sense if you have easy-to-dig soil or are renting a trench digger.