Quick Answer: How to Refill Trimmer Line
Turn off the trimmer and disconnect power (remove the battery, unplug the cord, or kill the gas engine and let it cool). Pop off the spool cap, remove the spool, wind new line of the correct diameter in the arrow-indicated direction, leave roughly 6 inches of line trailing, then route those tails through the exit eyelets and snap the cap back on. Bump the head lightly on the ground to confirm the line feeds freely.
What Is Trimmer Line and Which Head Type Do You Have?
Scope note: This guide covers string trimmers (also called weed eaters or line trimmers) used for cutting grass and vegetation — not hair or beard trimmers.
Trimmer line is a monofilament strand — typically nylon or co-polymer nylon — wound on a spool inside the trimmer head. As the head spins at high speed, the exposed line cuts vegetation. The refill method depends entirely on which of the three head types your trimmer uses.
Bump-Feed Head
The most common type. A spring-loaded spool sits inside a plastic housing. Tapping the head on the ground releases a short length of fresh line through the exit eyelets. Bulk line is wound directly onto the spool.
Fixed-Line Head
Also called a pre-cut or star head. There is no spool to wind. Individual pre-cut lengths of line (typically 6–9 inches each) are pushed directly into eyelets or locking slots around the head. Popular on commercial and heavy-duty trimmers.
Auto-Feed Head
An automatic-advance mechanism feeds line without any bumping. Some auto-feed heads accept bulk line wound on a removable spool; others (notably Husqvarna’s T25 and many Ryobi auto-feed systems) require pre-wound replacement spools and do not accept loose bulk line — check your owner’s manual before purchasing bulk line for these heads.
How to Identify Your Head Type
- Button on the bottom of the head: bump-feed.
- Star-shaped head with multiple small eyelets around the rim, no button: fixed-line.
- “Auto” or “AFS” label on the housing, no bump button: auto-feed.
- Consult the model number label on the trimmer shaft and cross-reference with the owner’s manual if still unsure.
How to Choose the Right Trimmer Line Gauge and Length
Using the wrong diameter line is the single most common reason a refill fails. The correct gauge is printed on the spool housing cap or on a label inside the head. It is also listed in the owner’s manual and on the manufacturer’s website under your model number.
Common Diameters and Use Cases
| Diameter | Best For | Typical Power Source |
|---|---|---|
| 0.065 in (1.65 mm) | Light grass, thin weeds, small cordless trimmers | Corded or light-duty cordless |
| 0.080 in (2.0 mm) | Medium grass, general residential use | Cordless or light gas |
| 0.095 in (2.4 mm) | Heavy grass, thick weeds, semi-pro use | Mid-range gas or high-voltage cordless |
| 0.105 in (2.65 mm) and above | Dense brush, heavy commercial cutting | Full-size gas trimmer |
Line shape: Round line is the standard and suits most jobs. Twisted (spiral) line reduces noise slightly and cuts a cleaner edge. Serrated or multi-sided line cuts tougher vegetation faster but wears more quickly. Shape does not affect the winding or threading method.
How Much Line to Cut
The maximum line length per spool is printed on the spool housing — never exceed it or the cap will not seat properly. As a general starting point, 9 feet (roughly 2.7 m) per strand is typical for a residential bump-feed spool, but always defer to the figure on your specific spool label.
Safety Steps Before Refilling Any Trimmer Line
Complete all of the following before touching the head or spool.
- Cordless trimmer: Press the power button to off, then remove the battery pack.
- Corded electric trimmer: Release the trigger, then unplug the power cord from the wall outlet.
- Gas trimmer: Move the on/off switch to “off” or “stop,” wait at least 5 minutes for the engine and exhaust components to cool before handling. Many OEM manuals (including those for STIHL, Husqvarna, and Echo gas trimmers) explicitly warn against touching the head area while the engine is warm.
- Wear safety glasses — cut monofilament ends are sharp and can flick toward your face during threading.
- Work on a flat, stable surface so the spool components do not roll away.
How to Refill Line on a Bump-Feed Trimmer Head (Step-by-Step)
What You Need
- Replacement trimmer line in the correct diameter
- Scissors or wire cutters
- Safety glasses
Steps
- Remove the spool cap. Most caps unscrew counterclockwise (right-hand thread is standard, but confirm — some brands reverse this to prevent loosening during use; the cap will indicate which direction). Press the side tabs if present and pull straight off for tab-lock designs.
- Remove the spool and spring. Lift the spool out. Note the position of the spring underneath — it must return to the same orientation. Set spring and cap aside where they will not be lost.
- Clear old line and debris. Remove any remaining old line. Wipe the spool groove and interior of the housing clean of grass and dirt — debris causes the line to bind.
- Cut the replacement line to the correct length. Use the figure printed on the spool housing. For a dual-line spool, cut two equal lengths.
- Locate the anchor slot. This is a small notch or hole in the spool body. Insert approximately 1 inch of line into the slot to anchor it before winding.
- Wind in the arrow direction. An arrow molded onto the spool indicates the correct winding direction. Wind firmly and evenly, keeping each layer tight and flat — loose or crossed coils cause the line to weld together under heat from friction. For dual-line spools, most designs have two separate winding chambers divided by a central divider; anchor and wind each strand in its own chamber.
- Leave 6 inches (15 cm) of line trailing. Stop winding when approximately 6 inches remain unwound. Hook the trailing end into the holding notch on the spool rim to keep it from unwinding while you reassemble.
- Seat the spool. Lower the spool back into the housing over the spring, pressing it down until it seats fully.
- Route trailing line through exit eyelets. Pull the 6-inch tails out through the eyelets (the small guide holes in the side of the housing). The line should extend freely.
- Replace the spool cap. Align the cap and press or screw it back on until it clicks or seats firmly. The spool should move slightly up and down but not rattle excessively.
- Bump-test. On a patch of grass or gravel, tap the head firmly on the ground twice. Each tap should advance a short length of line. If the line does not advance, see the Troubleshooting section below.
How to Replace Line on a Fixed-Line Trimmer Head (Step-by-Step)
Fixed-line heads use pre-cut segments inserted individually. There is no winding involved.
Steps
- Power off as described in the safety section.
- Identify the eyelets or locking slots on the head. Fixed-line heads typically have 2, 4, or 6 insertion points arranged symmetrically around the head.
- Cut pre-cut segments to length. The correct length is printed on the head or in the manual — typically 6 to 9 inches per segment. Pre-cut line sold specifically for fixed-line heads (such as Oregon’s 20-piece packs) is cut to standard lengths, but you can cut from bulk line of the correct diameter.
- Insert each segment. Push one end of a segment into an eyelet hole until approximately equal lengths exit from both sides of the head (the line passes straight through a channel inside the head). Some heads use a locking tab that clicks to secure the line — press the tab before inserting and release it once the line is seated.
- Repeat for all eyelets. Fill every slot; a partially loaded fixed-line head vibrates unevenly and stresses the drive shaft.
- Confirm all segments are seated and none will pull free with light hand tension.
- No cap reassembly is required on most fixed-line heads. Power on and test.
Brand compatibility: Fixed-line heads accept any brand of line provided the diameter matches the head’s specification. The segment length tolerance is more important than brand.
How to Refill an Auto-Feed Trimmer Head (Step-by-Step)
Auto-feed heads vary more between brands than bump-feed heads. Always check the owner’s manual for your specific model. The two main scenarios are covered below.
Scenario A: Auto-Feed Head With a Removable Spool (Accepts Bulk Line)
- Power off.
- Locate and open the loading port or remove the spool. Many auto-feed heads have a top-access port or a release tab on the side. Remove the spool the same way as a bump-feed head.
- Wind bulk line onto the spool following the arrow direction, using the correct diameter and not exceeding the maximum length printed on the spool.
- Seat the spool and route line through the eyelets.
- Replace the cover. The auto-feed sensor (typically a centrifugal mechanism) will advance line automatically during use as the head spins up to speed.
- Test: Start the trimmer and let it run at full throttle briefly. The line should advance to the correct cutting length automatically within a few seconds. If it does not, see Troubleshooting.
Scenario B: Auto-Feed Head Requiring Pre-Wound Replacement Spools
Some auto-feed systems — including several Husqvarna T25 variants and many Ryobi auto-feed models — are designed to use pre-wound, brand-specific replacement spools and are not intended to be rewound with bulk line. Using bulk line in these heads can damage the auto-feed mechanism or void the warranty.
- Power off.
- Press the spool release tabs on the side of the head and pull the spent spool straight out.
- Insert the replacement pre-wound spool (ensure the diameter matches the head’s spec) until it clicks into place.
- Route the line tails through the exit eyelets.
- Test at full throttle. The auto-feed should advance line within seconds.
Quick-Reference: Head Type vs. Refill Method
| Head Type | Refill Method | Line Format | Approx. Refill Time |
|---|---|---|---|
| Bump-Feed | Wind bulk line onto removable spool in arrow direction | Bulk line (cut to length) | 3–7 minutes |
| Fixed-Line | Insert pre-cut segments into individual eyelets | Pre-cut segments | 1–3 minutes |
| Auto-Feed (bulk-compatible) | Wind bulk line onto removable spool; auto-advance handles feeding | Bulk line (cut to length) | 3–7 minutes |
| Auto-Feed (spool-only) | Swap entire pre-wound spool cartridge | OEM or compatible pre-wound spool | Under 1 minute |
Troubleshooting: Common Problems After Refilling Trimmer Line
Line Won’t Advance After Refilling (Bump-Feed)
Most commonly caused by line wound in the wrong direction — the spring cannot push the spool far enough to release line through the eyelets. Remove the spool and rewind in the direction indicated by the arrow. Also check that the cap is fully seated; a partially secured cap blocks the bump mechanism.
Line Breaks Immediately
The line gauge is too thin for the vegetation being cut, or the line is old and brittle (nylon absorbs moisture over time, which paradoxically makes stored line more brittle when dry). Replace with the correct diameter line and soak new bulk line in water for 24 hours before winding — this restores flexibility and reduces breakage during cutting.
Trimmer Line Welds or Fuses Together on the Spool
Caused by loose or crossed winding — when coils shift during use, friction from the spinning spool generates enough heat to fuse monofilament strands together. Rewind tightly, keeping each layer flat and parallel. Also confirm you are not exceeding the maximum line length printed on the spool housing, as overfilling compresses the coils.
Spool Cap Won’t Close After Refilling
Too much line has been loaded onto the spool. Remove the spool and trim the line back so the total wound length does not exceed the maximum stated on the housing. Also confirm the spring is seated correctly underneath the spool — a dislodged spring raises the spool height and prevents the cap from closing.
Auto-Feed Not Advancing Line After Refilling
Check whether the line exits cleanly through both eyelets — if one tail is caught inside the housing, the auto-feed sensor cannot function symmetrically. Remove the spool, re-route both tails, and reseat. Also confirm you are using bulk line in a head designed for it; forcing bulk line into a spool-only auto-feed head will jam the mechanism.
Frequently Asked Questions
How often should I refill trimmer line?
Refill whenever the cutting line wears down to roughly 2–3 inches in length, or when the trimmer motor sounds like it is working harder than normal with no visible vegetation being cut. For regular residential use, this typically means refilling every 2–4 trimming sessions depending on terrain and vegetation density.
Can I use any brand of trimmer line as long as the diameter is correct?
Yes for bump-feed and fixed-line heads — diameter and shape are what matter, not brand. For auto-feed heads that specify OEM replacement spools (such as certain Husqvarna T25 and Ryobi auto-feed variants), using off-brand pre-wound spools may void the warranty; bulk line should not be substituted in those systems at all.
Which direction do I wind trimmer line onto the spool?
Always follow the arrow molded onto the spool body. The arrow indicates the winding direction relative to how you hold the spool — not relative to the trimmer head. Most spools wind counterclockwise when viewed from the bottom (cap side), but this is not universal. Winding against the arrow is the leading cause of line-feed failure.
Why does my trimmer spool keep running out of line so fast?
Three main causes: the line diameter is too thin for the work being done and wears quickly; the user is tapping the bump head too frequently or is cutting at too steep an angle into hard surfaces (concrete, stone edging) which shears the line rapidly; or the exit eyelets are worn or have a sharp burr that cuts the line as it feeds. Inspect the eyelets — if they are grooved or rough, the entire head may need replacement.
