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Using conduit

For outdoor wiring—hooking up a hot tub, adding outlets to a deck, powering a shed—installing conduit makes a lot of sense, and many times it’s required. Conduit even has its uses inside, wherever wires would otherwise be exposed and could be damaged. And if you have a circuit you may want to extend someday, conduit will enable you to pull additional wires.

We’re going to show you how to install plastic (PVC) rigid conduit rather than metal conduit. Plastic conduit is less expensive, lighter and much easier to work with. Here are some great pro tips from commercial electricians to help you make wiring runs with conduit.

Schedule 40 vs. 80

Buy THHN wire

Larger conduit and bigger boxes

Install 3/4-in. conduit instead of 1/2-in. if (1) you need to pull more than three wires through one section of conduit; (2) there’s any chance you’ll add wires in the future; or (3) if you have a long and winding run. The 3/4-in. conduit doesn’t cost that much more, and it’s a heck of a lot easier to pull wire through. Whatever size conduit you use, don’t fill it more than 40 percent with wires.

Single-gang electrical boxes will work, but if you have two or more conduit sections connecting to one box, buy double-gang. The male connectors on the ends of the conduit take up quite a bit of room inside the box, leaving little room for devices. GFCI receptacles and other large devices, like dimmers, fit better in deeper boxes (2-1/8 in.).

Deburr with a utility knife

Conduit in a trench

If you’re running rigid PVC conduit, most trenches need to be 18 in. deep, but ask your electrical inspector how deep to dig the trench for your specific project. You can run Schedule 40 in a trench, but use Schedule 80 wherever the conduit comes up out of the ground (see “Schedule 40 vs. 80” above). Assemble all the conduit first and plop the whole thing into the trench when you’re done. Much easier and cleaner than working in a trench!

Conduit doesn't need primer

Some PVC pipes require primer, but you don’t need to use primer when gluing conduit and fittings. Home centers usually sell the appropriate cement near the the conduit and fittings.

Mount the box, then the conduit, then the box

It’s tempting to start by attaching all the boxes to the walls and ceiling first and then run the conduit, but don’t do it. It’s easier to secure one box and then run the conduit from that box to the next one. Fasten the second box to the wall or ceiling after you fasten it to the conduit. Then you won’t have to fight the conduit trying to bend it into position. This is especially important if you have two boxes in close proximity because it’s difficult to bend short sections of conduit.

Metal hangers work best

Cut it with a circular saw

Install metal locknuts

Keep elbow totals no more than 360 degrees

Drill a hole to let water out

Hook on Old Wires to Pull New Ones

If you’re adding wires to existing conduit and have to pull them a long distance, hook the new wires to an existing one—including a replacement wire for the one you’re using—and pull them through that way. You’ll have to buy extra wire, but you’ll save a lot of time and frustration.

Pulling wires

Bushings protect wires

Use weatherproof boxes outdoors

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Cordless drill
    • Circular saw
    • 4-in-1 screwdriver
    • Needle-nose pliers
    • Lineman's pliers
    • Electrical tape
    • Utility knife
    • Wire stripper/cutter

You'll also need a metal cutting blade for the circular saw and work gloves.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • PVC conduit and fittings
    • THHN wire
    • Electrical boxes
    • PVC cement for conduit
    • Metal locknuts
    • Metal hangers
    • Plastic bushings

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Installing PVC Conduit

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