Direct Answer: How to Install Trimmer Line
To install trimmer line, twist or unclip the trimmer head cover counterclockwise, remove the old spool, cut a length of new line (typically 15–20 feet depending on your model), insert it into the anchor hole or slot on the spool, wind it tightly in the direction indicated by arrows, leave 4–6 inches unwound, thread the free end through the guide hole, and reassemble the head. The exact process varies by trimmer type—bump-feed, manual-feed, and automatic-feed trimmers have different loading mechanisms, but these universal steps apply across most models.
Understanding Your Trimmer Head Type
Before you attempt to load trimmer line, identify which mechanism your trimmer uses. Most residential string trimmers fall into three categories, and each requires a slightly different approach.
Bump-Feed Trimmers (Most Common)
Bump-feed trimmers automatically advance line when you tap the trimmer head against the ground. This is the most popular residential design. The spool holds pre-wound line, and when you bump the head, a spring-loaded mechanism feeds out a fresh length. This type requires you to wind line tightly onto the spool in a specific direction before reassembling.
Manual-Feed Trimmers
Manual-feed trimmers require you to manually pull out line and cut it to length when it becomes dull or breaks. These typically have two fixed anchor points on the spool rather than a rotating mechanism. Loading is simpler but requires precise threading.
Automatic-Feed Trimmers
Automatic-feed systems continuously advance line without bumping or manual intervention. These are often found on premium or commercial-grade trimmers. Line loading is usually the simplest of the three types, requiring only that you insert line into a slot and let the mechanism handle feeding.
How to Identify Your Trimmer Type
Check your trimmer’s manual or look at the trimmer head itself. Bump-feed heads are round with a visible spool inside. Manual-feed heads often have two line exits at the top. Automatic-feed heads may have a sealed design or a single line slot. Most consumer trimmers are bump-feed, so if you’re unsure, that’s likely what you have.
What You Need Before Starting
Gather the correct materials and tools before you begin. Having everything ready prevents mistakes and speeds up the process.
Trimmer Line Diameter
Trimmer line comes in standard diameters: 0.065 inches, 0.080 inches, and 0.095 inches. Check your trimmer’s manual or the label on your trimmer head to determine the correct size. Using the wrong diameter can prevent proper feeding or cause the line to break prematurely. Most residential trimmers use 0.080 inches, but verify before purchasing.
Tools and Materials You’ll Need
- Replacement trimmer line (correct diameter for your model)
- Scissors or line cutter (sharp scissors work well)
- Flathead screwdriver (optional, for some spool covers)
- Trimmer manual (for model-specific guidance and diagrams)
- Work surface (a table or workbench with good lighting)
Finding Your Trimmer’s Specifications
Your trimmer manual is the most reliable source. Look on the packaging, inside the manual’s cover, or on the trimmer head itself for line diameter specifications. Online manufacturer websites also provide manuals for most models. If you’ve lost the manual, search your trimmer brand and model number online—most manufacturers offer free PDF downloads.
How to Access and Remove Your Trimmer Head
The first step is safely accessing the trimmer head spool. This process is similar across most bump-feed and manual-feed trimmers.
Step 1: Prepare Your Trimmer
Unplug your electric trimmer or disconnect the spark plug wire on a gas trimmer. This prevents accidental startup while you’re working. Allow the trimmer to cool for a few minutes if you’ve been using it recently. Place the trimmer on a stable work surface with the head facing up.
Step 2: Remove the Trimmer Head Cover
Most trimmer head covers are held on by a single bolt or a snap-fit design. For bolt-on covers, use a flathead screwdriver to turn the bolt counterclockwise (lefty-loosey). For snap-fit covers, locate the tabs or clips and gently pry them apart using a flathead screwdriver. Turn counterclockwise if there’s a threaded center cap. The cover should come free in one or two rotations.
Step 3: Remove the Old Spool
Lift off the trimmer head cover completely. You’ll see the spool holding the old line. Most spools twist off counterclockwise or pull straight up if they’re on a removable shaft. Some trimmers have a fixed spool that doesn’t come out; in these cases, you’ll wind new line directly onto the existing spool after removing the old line. If the spool twists, rotate it counterclockwise until it comes free. Set it aside in a safe place.
Step 4: Remove Remaining Old Line
Pull off any remaining line from the spool by hand. Dispose of it in the trash. If line is wound tightly and won’t pull free, use scissors to cut it away. Clean out any debris, grass, or dirt from inside the trimmer head cavity before installing new line.
Loading New Line on the Spool: Bump-Feed Mechanism (Most Common)
Bump-feed is the most popular residential trimmer type, so we’ll cover it in detail. If your trimmer is manual-feed or automatic-feed, skip to the relevant section below.
Step 1: Cut the Trimmer Line to Length
Cut a single piece of trimmer line to the correct length. For most residential bump-feed trimmers, this is 15–20 feet. Check your manual for the exact recommended length. Cut the line straight across using sharp scissors. A crooked cut can catch inside the spool and cause jams. If you’re unsure of the exact length, err slightly longer—you can trim excess after winding.
Step 2: Locate the Anchor Hole on the Spool
Examine the spool carefully. You’ll see a small hole or slot near the center or edge—this is the anchor hole. Some spools have a notch instead of a hole. This is where the line begins its wind. Look for arrows printed on the spool indicating the correct winding direction; these arrows are crucial for proper operation.
Step 3: Insert the Line into the Anchor Hole
Take one end of your cut line and insert it firmly into the anchor hole. Push it in until it’s seated securely. You should feel slight resistance. Some anchor holes have a small latch or lip that holds the line in place; ensure the line is fully engaged before proceeding.
Step 4: Wind the Line Onto the Spool
This is the most critical step. Rotate the spool in the direction indicated by the printed arrows. Wind the line tightly and evenly, keeping tension on the line with your other hand so it doesn’t slip or bunch up. Wind tightly—loose winding causes tangles and feeding problems. Make sure each wrap sits neatly against the previous one without overlapping or gaps. Continue winding until you have 4–6 inches of line remaining unwound.
Step 5: Leave the Correct Amount of Line Unwound
Stop winding when 4–6 inches of line remains free. This length is critical: too little, and the line won’t reach the guide holes; too much, and it can tangle. Hold the wound spool firmly to keep tension and prevent unraveling.
Step 6: Locate the Guide Holes
Look at the trimmer head housing. You’ll see one or two small holes in the side or top—these are the guide holes (or eyelets). On dual-line trimmers, there are typically two holes positioned opposite each other. On single-line trimmers, there’s one hole.
Step 7: Thread the Line Through the Guide Hole
Take the free end of the unwound line and thread it through the guide hole. For dual-line trimmers, position the line so that it exits on both sides of the head. The line should sit snugly in the eyelet. You may need to gently wiggle the spool to position the line correctly. Ensure the line is not twisted or kinked.
Step 8: Reassemble the Trimmer Head
Place the spool back into the trimmer head, aligning any tabs or notches with the head housing. Twist it clockwise (righty-tighty) until it seats fully. Reattach the trimmer head cover by twisting it clockwise until snug. Do not overtighten—firm is enough. Plug in your electric trimmer or reconnect the spark plug wire.
Step 9: Test the Installation
Before using the trimmer, manually bump the head gently against a hard surface (like concrete) a few times while the trimmer is unplugged. You should see a small amount of line advance. If no line advances, the spool may not be seated correctly, or the winding direction may be wrong. Disassemble and recheck. Once line advances smoothly, your trimmer is ready to use.
Loading New Line on the Spool: Manual-Feed Mechanism
Manual-feed trimmers are simpler to load because the line doesn’t need to be pre-wound onto a rotating spool.
Step 1: Prepare the Trimmer Head
Remove the trimmer head cover by turning it counterclockwise or unclipping it. Manual-feed heads typically have a fixed spool with two anchor points at the top or center.
Step 2: Cut Two Lengths of Line
For manual-feed trimmers with dual lines, cut two equal lengths of trimmer line, typically 12–15 feet each. If your manual-feed trimmer has a single line, cut one 15–20 foot length.
Step 3: Anchor Each Line
Thread one end of each line piece through the anchor points (or slots) on the spool. Ensure both lines are pulled taut and seated firmly in their anchor points. Some manual-feed heads have a small knot area or enlarged section at the anchor—insert the line and pull tight so it won’t slip.
Step 4: Thread Through the Guide Holes
Guide the free ends of each line upward and outward through the guide holes on the trimmer head housing. For dual-line manual-feed trimmers, each line should exit through its own hole on opposite sides of the head. Ensure the lines are not twisted or kinked.
Step 5: Reassemble and Trim Excess
Reattach the trimmer head cover and tighten it clockwise. Cut the free ends of the line with scissors so they extend just beyond the trimmer head—typically 2–3 inches of usable cutting line. Manual-feed trimmers let you cut to your preferred length, so adjust as needed.
Loading New Line on the Spool: Automatic-Feed Mechanism
Automatic-feed trimmers are the simplest to load because the mechanism handles line advancement automatically.
Step 1: Remove the Trimmer Head Cover
Unclip or unscrew the trimmer head cover as you would with other trimmer types. Automatic-feed heads usually have a sealed or partially sealed design.
Step 2: Cut a Single Length of Line
Cut one piece of trimmer line to the recommended length (typically 15–20 feet). Check your manual for the exact specification.
Step 3: Insert the Line into the Feed Slot
Locate the line feed slot or opening on the automatic-feed spool. Insert one end of the line into this slot. The mechanism is designed to accept line without manual winding—simply push the line in firmly and let it seat fully.
Step 4: Wrap or Position the Line
Depending on your automatic-feed model, you may need to wrap the line loosely around the spool one or two times, or simply let it sit in the slot. Follow your manual for your specific model. Most automatic-feed systems have clear guides or grooves molded into the spool.
Step 5: Reassemble the Head
Reattach the trimmer head cover by twisting it clockwise until snug. Plug in or reconnect your trimmer. Automatic-feed systems typically begin feeding line as soon as you start using the trimmer, so no manual bumping is required to test it.
Common Mistakes and How to Avoid Them
Even experienced users occasionally make these errors. Knowing what to watch for will save you time and frustration.
Mistake 1: Winding Line in the Wrong Direction
Problem: Line doesn’t advance, or the spool jams when you bump the trimmer head.
Solution: Always follow the arrows printed on the spool. Winding against the arrows prevents the bump-feed mechanism from releasing line. If line doesn’t advance after bumping, disassemble the head and rewind in the correct direction. This is the most common error and the easiest to fix.
Mistake 2: Leaving Too Much or Too Little Line Unwound
Problem: Line tangles inside the head, or the free line is too short to thread through the guide hole.
Solution: Always leave 4–6 inches of unwound line. Measure this carefully before threading through the guide hole. If you’ve already wound too much, unwind a bit and adjust. If you wound too little, unwind everything and start over with a longer initial line length.
Mistake 3: Not Winding Tightly
Problem: Line tangles, jams, or doesn’t advance smoothly.
Solution: Wind with consistent tension, keeping the line tight against the spool at all times. Loose winding creates gaps and bunches that catch inside the head. Practice maintaining steady pressure with your non-winding hand to keep tension on the line.
Mistake 4: Using the Wrong Line Diameter
Problem: Line doesn’t feed, breaks frequently, or feels loose in the guide hole.
Solution: Always verify the correct diameter on your trimmer’s manual or the label on the trimmer head. Double-check before purchasing. If you’ve already installed the wrong diameter, remove it and purchase the correct size.
Mistake 5: Not Fully Seating the Spool or Head Cover
Problem: The spool rattles, line doesn’t advance, or the head cover is loose after use.
Solution: After assembling, give both the spool and the head cover a firm twist to ensure they’re fully seated. They should feel snug with no play or movement. If something feels loose, disassemble and reseat.
Frequently Asked Questions
How long should trimmer line be when I load it on the spool?
Most residential bump-feed trimmers use 15–20 feet of line per spool. Manual-feed and automatic-feed trimmers may differ slightly. Always check your trimmer’s manual for the exact recommended length. Using too little means fewer passes before reloading; using too much causes tangles and winding difficulties.
What should I do if my line keeps breaking or doesn’t advance after I bump the head?
First, check that you wound the line in the correct direction by looking at the arrows on the spool. If that’s correct, verify you’re using the right line diameter. If those are fine, disassemble the head, remove the line, and reload it, making sure to wind tightly and leave exactly 4–6 inches unwound. Improper winding is the most common cause of feeding problems.
Can I use any trimmer line, or does it have to match my trimmer brand?
Trimmer line is universal by diameter, not by brand. What matters is the diameter (0.065″, 0.080″, or 0.095″)—not the trimmer brand. You can use any manufacturer’s line as long as the diameter matches your trimmer’s specifications. Generic store-brand line works just as well as premium branded line.
Why won’t my trimmer head cover twist off?
The cover may be over-tightened or you may be turning it the wrong direction. Always turn counterclockwise (lefty-loosey) to remove. If it’s stuck, try placing a rubber band or old cloth under your palm for extra grip, and use steady, firm pressure rather than hard jerking. If it’s severely stuck, let the trimmer sit in warm water for a few minutes to help loosen any dried sap or debris, then try again.
Final Tips for Success
Work in good lighting so you can see the anchor hole and guide holes clearly. Take your time winding—rushing leads to mistakes. If something doesn’t feel right during reassembly, stop and recheck rather than forcing it. Keep your trimmer manual nearby for reference, and don’t hesitate to consult the manufacturer’s website if you get stuck. With practice, reloading trimmer line becomes quick and routine.
