String trimmer line usually breaks because the line is the wrong size, installed incorrectly, routed through a damaged eyelet, or being used against hard surfaces. Check the line, spool, head, and trimming technique in that order before replacing the trimmer.
What do you need help with?
Open an answer, or tell us what we should cover next.
Answered in this guide
Fix string trimmer line that keeps breaking
Check the line size and condition, spool winding, eyelets, trimmer head, head operation, reload method, and trimming technique. Most repeated breaks come from unsuitable or brittle line, poor installation, damaged contact points, dragging, or impacts with hard objects.
Use the diameter specified for the trimmer and cutting head. Line that is too large can bind or feed poorly, while an unsuitable size can break during use or place extra strain on the head.
Find spool and head problems that break trimmer line
Inspect the winding pattern, spool, eyelets, and head for crossed line, binding, sharp exit points, wrapping, packed debris, dragging, or other damage. A problem at one repeatable exit point often identifies the source of the breakage.
Change trimming technique to make line last longer
Use the outer part of the cutting arc and move gradually through tall or dense growth. Avoid forcing the line into concrete, fences, rocks, and other hard objects, which can cause correctly installed line to break quickly.
Requests help us prioritize the next guide. No email required.
One anonymous request per topic.
String trimmer line keeps breaking when it is the wrong diameter, brittle from age or heat, wound incorrectly, or repeatedly striking concrete, fences, rocks, and other hard surfaces. Start by checking the line size and condition, then inspect the spool, eyelets, and head. If those parts are sound, adjust your trimming technique and loading method before suspecting the motor.
1. Check that the line is the correct size
String trimmers are designed for a specific line diameter range. Line that is too thick can overload the head or motor, while line that is too thin may snap quickly in heavier grass and weeds.
Check the trimmer's owner's manual, label, or manufacturer's instructions for the approved diameter. Do not choose line only by appearance. The correct size depends on the trimmer's power, head design, and intended use.
Also check the line shape. Round, square, twisted, and serrated lines can behave differently, and some heads are intended for particular line types. If the line was recently changed, reinstall the recommended type and size before troubleshooting anything else.
2. Replace old, brittle, or heat-damaged line
Trimmer line becomes less flexible as it ages. Line stored in direct sunlight, a hot shed, or a vehicle can become brittle and break with light contact.
Look for line that is:
Dry, cracked, chalky, or visibly brittle
Flattened or kinked from being tightly stored
Discolored from heat or sunlight
Difficult to bend without snapping
Remove the old line and load fresh line from a sealed package. Store unused line in a cool, shaded place. Some manufacturers recommend soaking certain nylon lines in water to restore flexibility, but follow the line maker's instructions rather than assuming all line should be soaked.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
3. Inspect the spool and winding pattern
Poor winding can cause the line to cross over itself, bind in the spool, or feed unevenly. The sudden release of a stuck section can then snap the line at the eyelet or inside the head.
With the trimmer switched off and disconnected from its power source:
Remove the spool or bump-feed cap according to the manual.
Clean out grass, dirt, and melted plastic.
Check for cracks, warped plastic, or a damaged center hub.
Wind the line in the direction marked on the spool.
Keep each wrap neat and next to the previous wrap.
Do not overfill the spool.
Leave the specified amount of free line at each end.
If the spool is cracked, badly worn, or no longer holds the line securely, replace it with a compatible spool rather than trying to repair it.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
4. Check the eyelets and trimmer head
The eyelets are the openings where the line exits the head. A sharp edge, burr, missing guide, or worn eyelet can cut the line every time it rotates.
Turn off the trimmer and inspect both exit points. Run a fingertip carefully around the plastic or metal opening, watching for sharp damage. Do not force your finger into a narrow opening; use a cloth or cotton swab if needed.
Replace the eyelet, guide, cap, or complete head if the manufacturer supplies it as a service part. A damaged head can continue breaking new line, so changing line alone may not solve the problem.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
5. Avoid wrapping the line around the head
Line can break at the head if it is routed incorrectly or trapped under the spool. Compare the installation with the diagram in the owner's manual. The line should exit through the intended guides and move freely when the spool is turned by hand.
For bump-feed heads, make sure the cap, spring, spool, and retaining parts are assembled in the correct order. A missing or incorrectly positioned spring can prevent proper feeding and create excess tension on the line.
Never modify the head to accept more line than specified. Overfilling can cause binding, overheating, and repeated breakage.
6. Change your trimming technique
Even correctly installed line will break quickly when it repeatedly hits hard objects. Use the outer portion of the line's cutting arc and move gradually through tall or dense growth instead of forcing the head into it.
Common causes of impact breakage include:
Striking concrete, asphalt, brick, or stone
Hitting chain-link fencing or metal edging
Cutting directly against tree trunks or masonry
Allowing the line to contact curbs and walls
Moving too quickly through thick, woody weeds
Using a light-duty trimmer for brush it was not designed to cut
Keep the head parallel to the ground for ordinary grass unless the manual specifies another position. Near obstacles, slow down and leave a small margin that can be finished with a more suitable tool. For heavy brush, use only a blade or brush-cutting attachment approved for that trimmer and installed according to the manufacturer's instructions.
7. Check for a head that is spinning too fast or dragging
If the line breaks during normal grass trimming, inspect how the head operates. A head that drags against the ground, is packed with wet grass, or has a damaged bearing or cover can put unusual stress on the line.
Switch off the trimmer, disconnect the battery or unplug it, and clear packed debris. The head should rotate freely by hand when the trimmer is safely disabled. Do not operate the tool with a cracked guard, loose head, missing fastener, or damaged shaft.
If the head vibrates heavily, makes unusual noise, or becomes excessively hot, stop using the trimmer. Those symptoms can indicate a damaged head, shaft, gearbox, or motor and may require a qualified repair technician.
8. Reload the line correctly
A reliable reload depends on using the exact line length and routing shown in the manual. General steps are:
Remove the power source before opening the head.
Clean the head and spool.
Cut line to the manufacturer's recommended length.
Wind it tightly and evenly in the marked direction.
Keep the line under the spool's retaining tabs if present.
Feed both ends through the correct eyelets.
Reassemble the head fully before reconnecting power.
Confirm that the line extends evenly and is not trapped.
Avoid pulling excessive line from the head to compensate for poor feeding. If the automatic or bump-feed mechanism does not release line correctly, inspect the cap and spool for wear or replace the feed components.
When should you replace the head or trimmer?
Replace the spool or head when it has cracked, warped, developed sharp exit points, or repeatedly damages correctly sized fresh line. A replacement head is also reasonable when the feed mechanism is worn and replacement parts are unavailable or cost nearly as much as a compatible head.
Consider replacing the trimmer when the head is sound, the correct line is installed, and the line still breaks during light work—especially if the tool vibrates, overheats, loses power, or has a damaged shaft or gearbox. Stop using it and follow the manufacturer's service guidance for electrical or motor faults. Do not bypass guards or attempt repairs to energized wiring.
Quick diagnosis
Line snaps immediately after loading: Check the diameter, winding direction, line length, and spool assembly.
Line breaks at one specific exit point: Inspect that eyelet for a burr, crack, or missing guide.
Line breaks only near concrete or fences: Change technique and keep the cutting arc away from hard surfaces.
Line breaks after storage: Replace brittle or heat-damaged line.
Line feeds poorly and then snaps: Clean the head and inspect the spool, spring, cap, and retaining tabs.
Fresh line breaks during light grass trimming: Check for a damaged head, excessive vibration, or a mechanical fault.
FAQ
Why does my string trimmer line break as soon as I start it?
The line may be the wrong diameter, wound in the wrong direction, too long for the spool, or trapped under the spool or cap. Remove the power source, reload the line according to the manual, and inspect the eyelets for sharp damage.
Does thicker trimmer line stop it from breaking?
Not necessarily. Thicker line can last longer in suitable heavy-duty equipment, but it can overload a trimmer designed for thinner line. Use only the diameter and line type approved for your specific model.
Why does my trimmer line keep breaking at the eyelet?
A burr, crack, worn guide, or sharp edge at the eyelet can cut the line repeatedly. Replace the damaged eyelet or compatible head, and do not continue using a head with cracked or sharp parts.
Should I soak string trimmer line in water?
Some nylon lines may benefit from water storage or soaking, but recommendations vary. Check the line manufacturer's instructions. Replacing brittle line and storing new line away from heat and sunlight is the safer general fix.
