How to Replace a String Trimmer Spool in 5 Minutes

Most cordless and corded string trimmers use a pre-wound auto-feed spool. When the line runs out, you don't need to rewind anything — you swap in a new spool. It takes about five minutes and no tools.

Before you start

• Check that the replacement spool is listed for your trimmer's model number, and that it's the right type: single line or dual line.
• Remove the battery or unplug the trimmer. Never work on the head while the tool can start.
• Let the head cool down if you've just been cutting.

Step by step

1. Remove the spool cap. Press the two tabs on the sides of the cap (or twist it counter-clockwise, depending on the model) and lift it off.
2. Take out the old spool. Pull it straight up. Remove any short pieces of old line from the head and the eyelets.
3. Clean the head. Brush out grass and dirt. Check the spring (if your head has one) and the eyelets for wear.
4. Unhook the line ends on the new spool. Pre-wound spools have the line ends clipped into notches. Free them and leave about 4–6 in (10–15 cm) of line.
5. Thread the line through the eyelets. Feed each end out through the eyelet on the head. Dual-line spools have one line per side.
6. Seat the spool. Press it down into the head, turning it slightly until it drops into place.
7. Refit the cap. Line up the tabs and push until both sides click. Tug the cap gently to confirm it's locked.
8. Test. Refit the battery or plug in, and run the trimmer briefly. The cut-off blade on the guard trims the line to the right length automatically.

Troubleshooting

• Line won't feed: the line may be wound loosely or crossed. Remove the spool and check that the line comes off smoothly in the direction of the arrow on the spool.
• Line keeps breaking: old line gets brittle. Store spare spools out of direct sun, and cut along edges with the tip of the line rather than pushing into fences or concrete.
• Cap won't lock: check that the spool is fully seated and the line isn't trapped under the cap.

Keep a spare spool or two on hand — running out halfway through the lawn is the most common reason a job stops.