The basic steps to load new line into your trimmer head
Most weed trimmers use one of two line-loading systems: the bump-feed head, where you tap the trimmer head on the ground to release more line, and the fixed-spool head, where you manually wind line onto a spool inside the head. The process differs between them, but both take about five minutes once you have the right line diameter for your model.
Before you start, check your trimmer's manual or the label on the head itself to find the correct line diameter — usually 0.065, 0.080, or 0.095 inches. Using the wrong size can jam the head or cause the line to break constantly. Buy a spool of replacement line at any hardware store or online; a universal spool costs between $5 and $15 and lasts through multiple refills.
Key Takeaways
- Check your trimmer head or manual for the correct line diameter before buying replacement line, as using the wrong size causes jams and breakage.
- Bump-feed heads require you to wind line into the spool chamber, tap the head on the ground to advance it, and trim the excess with scissors.
- Fixed-spool heads need you to remove the spool, wind line onto the posts inside, and reassemble the head in the correct order.
- If your trimmer head is cracked, leaking fuel, or the line will not advance, replace the entire head rather than trying to refill it.
How to refill a bump-feed trimmer head
Bump-feed heads are the most common type on consumer trimmers. Start by removing the head from the trimmer shaft — most heads twist counterclockwise by hand, though some require a wrench. Once the head is off, look for the access hole or cover on the bottom or side. Some heads have a removable cap; others have a slot you can pry open with a flathead screwdriver.
Cut a length of line about 20 feet long. Feed one end into the access hole and wind it tightly around the spool inside, following the direction of the arrow printed on the head. Wind until you have about 2 feet of line left, then feed the remaining length back out through the exit holes on the side of the head. Trim any excess with scissors so the line extends about 2 inches beyond the head. Screw the head back onto the trimmer shaft, and you are done — the next time you tap the head on the ground, it will advance fresh line.
How to refill a fixed-spool trimmer head
Fixed-spool heads are less common but still appear on many electric and battery trimmers. Remove the head from the trimmer and locate the two screws or clips holding the spool cover in place. Remove the cover and lift out the spool — it usually sits on a central post with a spring underneath.
Cut two lengths of line, each about 15 feet long. Look for two posts or hooks inside the spool chamber. Insert one end of the first line into the slot on one post, then wind the line tightly around the spool in the direction of the arrow. When you reach the end of the post, move to the second post and repeat with the second length of line. Leave about 6 inches of line extending from each post, then reassemble the spool, spring, and cover in reverse order. Thread the two line ends through the exit holes in the head cover before screwing it back onto the trimmer.
Trimming the line to the correct length
Once the head is back on the trimmer, the line should extend about 2 inches beyond the edge of the head for bump-feed models and 3 to 4 inches for fixed-spool models. If it is longer, trim it with scissors or a utility knife while the trimmer is off and unplugged. Line that is too long will slow the trimmer and cause uneven cutting; line that is too short will not reach the grass.
After your first use, check the line again. It will wear down quickly during the first few minutes of trimming, and you may need to trim it back to the correct length once more. After that, the bump-feed mechanism or your manual advancement will keep the line at the right length.
When to replace the entire head instead of refilling
If the head is cracked, leaking fuel, or the line will not advance no matter how many times you tap it or wind it, the head itself has failed and needs to be replaced. A new trimmer head costs $15 to $40 depending on the model and brand. Check your trimmer's manual or the label on the current head to find the correct replacement — heads are not universal and must match your trimmer shaft diameter and thread type.
If the spool inside a fixed-spool head is stripped or broken, you can sometimes buy a replacement spool alone for $8 to $12, which is cheaper than a full head. Check whether your model supports this before ordering.
Choosing the right line diameter and material
Line comes in different diameters and materials. Standard nylon line is the most common and works for most residential trimming. Thicker line (0.095 inches) cuts tougher weeds and brush but uses more fuel and wears faster. Thinner line (0.065 inches) is lighter and lasts longer but breaks more easily on thick weeds.
Some trimmers accept twisted or square-profile line, which cuts more efficiently than round line but costs more. Check your manual to see whether your head is designed for round line only or can handle other profiles. Using the wrong profile can jam the head or cause the line to break constantly.
Troubleshooting line problems after refilling
If the line breaks when ready after refilling, you may have wound it too tightly, used the wrong diameter, or loaded it in the wrong direction. Remove the head, unwind the line, and try again, winding more loosely and checking the arrow on the head to confirm the direction. If the line still breaks, the head may be damaged inside — look for cracks or rough spots where the line exits.
If the line will not advance on a bump-feed head, the spool may be jammed with old line fragments. Remove the head, empty it completely, and refill with fresh line. If the line still will not advance after tapping, the internal mechanism is worn and the head needs to be replaced.
Frequently Asked Questions
Can I use any line diameter in my trimmer?
No. Using the wrong diameter can jam the head, cause the line to break constantly, or damage the trimmer. Check your manual or the label on the head for the correct size — usually 0.065, 0.080, or 0.095 inches — and buy line that matches.
How often do I need to refill the trimmer head?
It depends on how much you trim and how thick the weeds are. Most homeowners refill every two to four weeks during the growing season. You will know it is time when the line wears down to less than 1 inch beyond the head or breaks during use.
What should I do if the line keeps breaking?
Check that you are using the correct diameter and that you wound it in the right direction. If the line still breaks, the head may have cracks or rough spots inside where the line exits. Inspect the head for damage, and replace it if you find any.
Is it cheaper to refill the head or buy a new one?
Refilling is much cheaper — a spool of line costs $5 to $15 and refills the head many times. A new head costs $15 to $40. Refill the head as long as it is not cracked or damaged.
Do I need to drain the fuel before replacing the line?
For gas trimmers, it is safer to let the engine cool and drain the fuel tank before removing the head, though not always necessary. For electric and battery trimmers, straightforward unplug or remove the battery before you start.