If you've never pulled wire through conduit, it may seem a bit troubling. How in the world can you get wire to push through conduit, especially when the conduit run may be hundreds of feet long? Unless the conduit is very short and/or perfectly straight, pushing it through is highly unlikely. And, of course, it won't just crawl through the pipe itself. Dry and bare wiring being pulled through conduit, especially PVC conduit, creates friction, making it even more difficult to pull the wire.
There are a few basic tools and supplies that can help make pulling wire through conduit a snap.
Using a Mouse
No, I'm not talking about a specially trained mouse that climbs through the conduit while clenching the wires in its teeth (although that would be pretty cool). A conduit mouse, also called a conduit piston, is a small cylinder of foam that is slightly smaller that the interior diameter of the conduit. It has a wire running through it with a loop on each end. You tie strong string, called a pull string, to one of the loops, then suck the cylinder through the conduit using a shop vac. When the mouse, with the string attached, reaches the other end, you secure the wires to the string then pull them back through the conduit using the string. You can buy a conduit mouse individually or get a set of them with different diameters. As a budget substitute, you can also use a plastic grocery bag or a balled up piece of foam, although these tend to work best with large conduit, such as 2" or larger PVC.
Using a Fish Tape
The most commonly used tool for pulling wire through conduit is a fish tape. A fish tape is an electrician's tool with a long, flat metal wire wound inside a wheel-shaped spool. The end of the tape has a hook on it. You feed this end into one end of the conduit and push the tape through the conduit, unwinding from the spool as you go.
When the tape reaches the other end of the conduit, you secure the wires to the hook on the tape then pull the tape back through the conduit with the wires in tow. Fish tapes are widely available in a range of lengths starting at 25'. There are also nylon tapes that don't include a spool; these may be the most economical option for when you need a fish tape only for small jobs.
Lubricating the Wires
Pulling wires can be difficult enough through straight runs of conduit, but throwing a few bends and turns in the run increases friction, making pulling much more difficult. That's when you use a lubricant. Wire-pulling compound is a non-conductive lubricant in either a gel or slimy, soapy form that makes both the conduit and wires slick by coating the wiring, allowing it to slide through the conduit with relative ease. Apply compound directly to the wires before pulling them into the conduit. Use the lubricant more heavily at the beginning of the pull and less so towards the end of the pull, as the interior of the conduit will become coated along its length as you pull. Follow the manufacturer's instructions for proper application.