The fastest way to reload your weed wacker
Most weed wackers use one of two systems: a bump head that advances line when you tap the bottom on the ground, or a manual-advance head where you pull out the old line and wind new line by hand. The bump head is simpler—you just pop off the spool, pull out the spent line, and feed in a new pre-cut length. The manual head takes a few more steps because you have to wind the line yourself, but both jobs take less than five minutes once you know the order.
The line itself comes in different thicknesses, measured in thousandths of an inch. Your weed wacker's manual or the head itself will tell you the right thickness—common sizes are 0.065 inch, 0.080 inch, and 0.095 inch. You can buy spools of line at any hardware store, garden center, or online. Some people buy pre-wound spools that drop straight in; others buy bulk line and wind it themselves to save money.
Key Takeaways
- Bump heads let you straightforward pull out old line and feed in new line without winding; manual heads require you to wind the line around the spool yourself.
- Check your weed wacker's manual or the head itself to find the correct line thickness before you buy replacement line.
- Pre-wound spools cost more but save time; bulk line costs less but requires you to hand-wind the spool.
- Always unplug or turn off the weed wacker and let it cool for a few minutes before you open the head.
How to replace line on a bump-feed head
Unplug the weed wacker or turn it off and let it sit for two or three minutes so the head cools down. Locate the spool inside the head—it's the plastic cylinder that holds the line. Most bump heads have a center bolt or a clip that holds the spool in place. Turn the bolt counterclockwise by hand or with a wrench, or press the clip inward to release it.
Pull the spool straight out and look at how the old line is wound around it. You'll see a notch or slot on the edge of the spool where the line feeds out. Pull out all the old line and throw it away. Cut a length of new line—usually 20 to 25 feet, though your manual may specify a different length. Feed one end of the new line into the notch on the spool and pull it tight so it sits in the groove.
Slide the spool back into the head, line the bolt or clip back up, and tighten it by hand. Don't over-tighten—snug is enough. Pull the line out through the exit holes on the sides of the head until you feel resistance, then trim it flush with the edge of the head using scissors or a utility knife. Plug the weed wacker back in and test it on a patch of grass.
How to replace line on a manual-advance head
Unplug the weed wacker and let it cool. Open the head by unscrewing the center bolt or unclipping the cover—the method depends on your model, so check your manual if you're not sure. You'll see two spools, one on each side, or sometimes a single spool with two chambers. Pull out all the old line and discard it.
Cut two lengths of new line, each about 15 to 20 feet long (check your manual for the exact length). Insert one end of the first length into the slot at the base of one spool and begin winding the line around the spool by hand, moving away from you. Wind it tightly and evenly, keeping tension on the line as you go. When you reach the end of the spool, tuck the line into the notch or slot at the edge to hold it in place. Repeat the same process on the other spool with the second length of line.
Close the head and tighten the center bolt or clip. Pull both lines out through the exit holes until they're even, then trim them to the same length with scissors. The lines should be about 2 to 3 inches longer than the diameter of the head. Plug the weed wacker back in and test it.
Choosing between pre-wound spools and bulk line
Pre-wound spools come fully loaded and ready to drop into your weed wacker. You straightforward remove the old spool, insert the new one, and trim the lines. This method costs more per use but saves time and eliminates the chance of winding the line wrong. Pre-wound spools work with both bump heads and manual heads, though you need to buy the right spool for your specific head model.
Bulk line comes on a large spool and you wind it yourself onto your weed wacker's spool. It costs less per foot than pre-wound spools, so if you use your weed wacker often, the savings add up. The trade-off is that winding takes practice—if you wind too loosely, the line won't feed properly; if you wind too tightly, it can jam. Many people find the savings worth the extra effort once they've done it a few times.
Check your weed wacker's manual to see which option your head supports. Some heads are designed for pre-wound spools only, while others work with either system. If you're new to weed wacker maintenance, a pre-wound spool is the safer choice.
What to do if the line keeps breaking or jamming
If your line breaks frequently during use, the thickness may be wrong for your weed wacker's power level. A line that's too thin will snap under load; a line that's too thick won't feed properly and can jam the head. Check your manual for the correct thickness and try a different size. Also inspect the exit holes on the head—if they're cracked or rough, they can fray and weaken the line. A cracked head usually needs to be replaced.
If the line jams when you try to feed it, the spool may be wound too tightly or the line may be tangled inside the head. Open the head, remove the spool, and unwind a few feet of line to loosen the tension. Rewind it more loosely and try again. If the line still jams, the head itself may be damaged or worn out, and you'll need to replace it.
If the line won't advance at all on a bump head, make sure you're tapping the bottom of the head firmly on the ground—a light tap won't trigger the advance mechanism. If you're tapping hard and nothing happens, the advance mechanism inside the head may be broken, which means the head needs replacement.
How to know when to replace the head itself
The head lasts much longer than the line, but it does wear out. Signs of a failing head include cracks in the plastic, a wobbly spool that won't stay centered, or line that won't feed no matter how you wind it. If the exit holes are enlarged or rough, the line will fray and break constantly. If the advance mechanism on a bump head stops working even after you've cleaned out any grass or debris, the internal spring or pawl has likely broken.
Replacement heads cost between $15 and $40 depending on the brand and model. They're usually held on by a single bolt or clip, so swapping one out takes about two minutes. Check your weed wacker's model number (usually stamped on the motor housing) and search for a compatible head online or at a hardware store. Bring your old head with you if you're buying in person—the staff can match it to the right replacement.
Frequently Asked Questions
Can I use a different thickness of line than what the manual says?
You can try a slightly different thickness, but staying within the range your manual specifies gives the best results. A line that's too thin will break easily; one that's too thick won't feed properly or may damage the motor. If you're between sizes, start with the thinner option and move up only if the line breaks constantly.
How often should I replace the line?
It depends on how often you use the weed wacker and the size of your yard. Most people replace the line every few weeks during mowing season, or whenever it breaks or wears down to less than an inch on each side. Keep spare line on hand so you're never stuck mid-job.
What's the difference between round and twisted line?
Round line is the standard type and works with almost all weed wackers. Twisted or spiral line is thicker and more durable, so it lasts longer and handles tougher weeds, but it costs more and may not fit all heads. Check your manual to see if your head supports twisted line before you buy it.
Do I need to replace the spool itself, or just the line?
Usually just the line. The spool is reusable and lasts for years. You only replace the spool if it cracks, warps, or the notches wear down so the line won't stay in place. Most people replace the entire head before the spool fails.
Can I wind the line in either direction on a manual head?
No—wind it in the direction your manual specifies, usually away from you. Winding it backward will cause the line to tangle and jam when you try to feed it out. If you're not sure which direction is correct, check your manual or look for an arrow printed on the spool itself.