How Do You Replace Weed Eater String? (Step-by-Step Guide)

Direct Answer: How to Replace Weed Eater String

To replace weed eater string, first disconnect the power source (unplug an electric model or remove the spark plug on a gas model). Next, identify your head type (bump-feed, manual-feed, or automatic-feed), remove the trimmer head or spool cover, and take out the old line. Cut a new piece of trimmer line in the correct diameter (typically 0.065–0.110 inch; check the label on your spool), wind it evenly onto the spool in the direction indicated by the arrows, feed the ends through the eyelets, and reassemble the head. Always work on a stable surface, wear gloves and eye protection, and avoid over-winding to prevent tangles.

Understanding Your Weed Eater’s Feed System

Before you touch the trimmer, you need to know which type of head you have. The restringing method differs slightly depending on the feed system, and using the wrong technique is the most common cause of frustration.

Bump-Feed Heads (Most Common)

Bump-feed heads, also called tap-and-go or Tap-N-Go heads, are standard on most consumer gas and electric string trimmers. To release more line, you tap the bottom of the head against the ground while the trimmer is running at full speed. Inside, a spring-loaded spool holds the line, and a bump knob releases a small amount of line each time you tap.

• How to identify: The head has a visible bump knob on the bottom, and the owner’s manual mentions “tap to advance.”
• Restringing note: You usually wind the line onto the spool and route both ends through eyelets on the head. Some bump heads use a single line looped through the center; others use two separate lines.

Manual-Feed (Fixed-Line) Heads

Manual-feed heads, sometimes called fixed-line or straight-shaft heads, hold a short piece of line that you extend by stopping the trimmer and pulling the line out by hand. There is no bump knob. These are common on lightweight electric trimmers and on some commercial models where operators prefer a fixed cutting width.

• How to identify: No bump knob; you see two short line ends sticking out of the head at all times.
• Restringing note: You typically remove the head, pull out the old line, and insert a new precut piece (often 8–10 feet) through the center hub, centering it so both ends are equal.

Automatic-Feed Heads

Automatic-feed heads advance line automatically whenever the engine or motor speed drops, usually when you press the trigger from idle. They are less common today but appear on some older and commercial trimmers.

• How to identify: The head has no bump knob, and the line advances on its own when you rev the throttle.
• Restringing note: Follow the same general winding procedure, but be careful not to over-wind, because the automatic mechanism depends on the line being loaded loosely enough to advance.

Locating Model and Line Specifications

Your trimmer’s model number is printed on a sticker or plate on the shaft or near the engine. The recommended line diameter is often printed directly on the spool, on the trimmer head, or in the owner’s manual. If you no longer have the manual, search online for “[brand] [model] trimmer line size” or check the manufacturer’s website. When in doubt, the most common consumer sizes are 0.065, 0.080, and 0.095 inch.

Safety and Preparation

Replacing trimmer line is a low-risk job, but a string trimmer can still injure you if it starts unexpectedly. Take these precautions before you begin.

Safety Precautions

• Disconnect the power source: For electric trimmers, unplug the unit or remove the battery. For gas trimmers, disconnect the spark plug wire and secure it away from the plug. Never rely on the switch being off.
• Wear gloves and eye protection: The line can snap, and the spool is spring-loaded on bump-feed heads. Safety glasses prevent debris from reaching your eyes, and gloves protect your hands from the cutting edges of the line and any grass buildup.
• Work on a stable, flat surface: A workbench or a clean patch of driveway is ideal. Avoid working on grass where small parts can be lost.
• Clean the head first: Built-up grass and dirt can make the spool hard to remove and can cause the new line to bind. Wipe the head with a rag before opening it.

Tools You May Need

• Work gloves and safety glasses
• Flathead screwdriver (for prying off caps or tabs on some heads)
• Needle-nose pliers (for removing stuck line or springs)
• Scissors or a sharp utility knife (to cut new line cleanly)
• A rag and, if needed, a small brush for cleaning
• New trimmer line of the correct gauge (check the spool label)

Step-by-Step Guide to Replacing the String

This universal procedure works for the vast majority of weed eaters. Read the steps once, then adapt them to your specific head type.

Step 1: Disconnect the Power Source

Unplug the electric trimmer, remove the battery, or pull the spark plug boot off the plug on a gas model. This is non-negotiable. The trimmer must be completely unable to start while your hands are near the head.

Step 2: Remove the Trimmer Head or Spool Cover

There are three common removal methods:

• Push-tab heads: Press the two tabs on the sides of the head and pull the cover off. The spool usually stays on the shaft.
• Screw-on caps: Turn the cap counterclockwise by hand or with a screwdriver if it has slots. Some caps are reverse-threaded, so check the arrows on the cap.
• Center-bolt heads: Hold the shaft with one hand (or use the hole provided for a hex key) and loosen the center bolt with a wrench. This is common on straight-shaft trimmers.

Once open, lift the spool out carefully. On bump-feed heads, a spring sits under or inside the spool; keep it in place or set it aside so it doesn’t bounce away.

Step 3: Remove the Old String

Pull the old line out of the spool. If it is tangled or welded together, cut it free with scissors or a utility knife. Clean any grass, dirt, and oil residue from the spool and the inside of the head with a rag. Check that the eyelets (the holes where the line exits the head) are clear; poke them clean with a small screwdriver if needed.

Step 4: Cut the New Line to the Correct Length and Gauge

Check the spool label or manual for the recommended diameter. Common consumer gauges are:

Using a line that is too thick can jam the head or overload the engine; too thin will break frequently. For most spools, cut a single piece of line about 20–25 feet long, or two pieces of 10–12 feet if your spool has two separate chambers. Some fixed-line heads require one precut piece of 8–10 feet; check your manual.

Step 5: Wind the Line Onto the Spool

Look for the arrows on the spool that indicate the winding direction. This is critical: winding the wrong way is the number one cause of line that won’t feed.

• Single-line spools: Insert one end of the line into the anchor hole in the center of the spool, then wind in the direction of the arrow. Keep the line tight and even, laying each wrap next to the previous one. Stop when the line is about 1/4 inch from the outer edge of the spool; do not overfill.
• Two-chamber spools: Insert the first line into one anchor hole and wind it into its chamber, then repeat with the second line in the opposite chamber. Keep the two lines in their own sections.

Pro tip: If the line keeps springing off, hold tension with your thumb while you wind. For bump-feed heads, some manufacturers recommend winding the line slightly loose so the bump mechanism can release it; check your manual. When in doubt, wind neatly and evenly—tangles almost always come from messy winding.

Step 6: Feed the Ends Through the Eyelets

Once the spool is wound, find the eyelets (the small holes or notches on the spool and on the head). Route each line end through its matching eyelet, pulling about 4–6 inches of line through so the ends are free. On a two-line head, both ends should stick out of the head when reassembled.

Step 7: Reassemble the Head

Place the spool back into the head, making sure the eyelets align with the exit holes. Reinstall the spring, cover, or center bolt in the reverse order of removal. If the head has tabs, press them until they click. If it has a cap, turn it clockwise until snug—do not overtighten, or the line will bind.

Step 8: Test the Feed

Reconnect the power source. Hold the trimmer away from your body and start it. For bump-feed heads, run at full throttle and tap the head on the ground; the line should advance and the cutter blade on the guard should trim the ends to the correct length. For manual-feed heads, stop the trimmer and pull the line ends to the desired length. If the line does not feed, see the troubleshooting section below.

Selecting the Correct Replacement Line

Choosing the right line is just as important as winding it correctly. The wrong diameter or shape can ruin your trimming experience.

Line Diameter

The diameter is measured in inches or millimeters and is printed on the spool label and the packaging. Match the manufacturer’s recommendation. A thicker line cuts heavier vegetation but requires more power and can damage a small electric motor. A thinner line is easier on the engine but breaks more often in thick weeds.

Line Shapes

• Round: The most common and versatile shape. It cuts well in light to medium vegetation and is the safest choice for beginners.
• Square or twisted: These shapes have sharper edges that cut through thick grass and weeds faster. They are slightly noisier and wear faster than round line.
• Star or serrated: Aggressive shapes for heavy brush and overgrown areas. They are louder and can be hard on the trimmer head, so use them only if your manual allows.
• Multi-sided (e.g., pentagon): A good compromise between cutting speed and durability for general yard work.

Brand and Quality Considerations

You do not need to buy the same brand as your trimmer, but you should buy a quality line. Cheap line is more prone to breaking, stretching, and welding together inside the head. Look for line labeled “heavy-duty” or “commercial” if you have tough vegetation. Also consider the line’s flexibility: softer line is easier to wind and is gentler on the feed mechanism, while stiffer line resists breakage but can jam in some heads.

Troubleshooting Common Issues

Even with careful winding, problems can occur. Here is how to fix the most frequent complaints.

The Line Won’t Feed Out

• Wound the wrong direction: The most common cause. Open the head, unwind the spool, and rewind following the arrows.
• Line is too short: If fewer than 4 inches of line protrude from the head, the feed mechanism cannot grab it. Pull more line through the eyelets.
• Spool is overfilled: The line binds against the head housing. Remove a few wraps and try again.
• Spring is missing or misaligned: On bump-feed heads, the spring drives the ratchet. Open the head and confirm the spring is seated correctly.
• Head is dirty: Grass packed around the spool can stop rotation. Clean the head thoroughly.

The Line Tangles or Welds Together

• Over-winding: Too much line on the spool presses the layers together. Keep the line 1/4 inch below the spool rim.
• Winding too loosely: Loose wraps cross over each other and tangle. Wind with steady tension, keeping each wrap flat.
• Wrong gauge: Line that is too thick for the head cannot move freely and may weld from friction. Switch to the recommended diameter.
• Line quality: Cheap line softens and fuses in hot weather. Try a higher-quality line.

The Line Breaks Constantly

• Line is too thin for the job: Step up to the next diameter if your trimmer can handle it.
• Cutting against hard surfaces: Trimming along concrete, brick, or fences wears line fast. Let the line do the work and keep the head slightly above the hard surface.
• Dull or damaged line: Replace the line if it has been stored for a long time or has kinks from being wound incorrectly.

The Head Vibrates or Won’t Spin Properly

• Uneven line length: Both ends should be roughly equal so the head stays balanced.
• Debris inside the head: Clean the spool and housing and check that the spring and washer are in place.
• Loose head: Tighten the center bolt or cap, but do not overtighten.

Frequently Asked Questions

How often should I replace weed eater string?

There is no fixed schedule. Replace the line when the cutting ends are worn down to about half their original length or when the line no longer feeds properly. With normal weekly trimming, a full spool typically lasts several weeks to a couple of months, depending on the vegetation and how often you hit hard surfaces.

Can I use any brand of trimmer line on my weed eater?

Yes. Trimmer line is largely universal as long as the diameter matches your head’s capacity. Check the spool label for the recommended gauge (usually 0.065 to 0.110 inch) and choose a reputable brand. Avoid mixing line diameters in a two-line head, as this causes uneven cutting and vibration.

Do I need to remove the entire trimmer head to replace the string?

Usually yes, but on many push-tab heads you only remove the cover, not the whole head assembly from the shaft. On screw-on cap heads, you remove the cap and the spool. Only center-bolt designs require removing the entire head from the driveshaft. In all cases, the process takes less than five minutes once you have done it a few times.

Why does my new line keep coming out of the spool?

The line is likely under-wound (too little line on the spool to hold itself in place) or the end was not anchored in the center hole properly. Rewind with firm, even tension and confirm the anchor end is seated in the slot. Also make sure you are routing the line through the eyelets before reassembling the head, because the eyelets hold the line in position.

What is the difference between a bump-feed and a fixed-line head?

A bump-feed head advances line when you tap the head on the ground while the trimmer is running, so you can add line without stopping. A fixed-line (manual-feed) head holds a set length of line that you extend by hand only when the trimmer is off. Bump-feed heads are more convenient for large yards; fixed-line heads are simpler and lighter.

Note: Always consult your trimmer’s owner’s manual for model-specific instructions, torque specifications, and recommended line gauge. If you are unsure about your head type or the correct line size, contact the manufacturer or a local small-engine repair shop.