Direct Answer: How to Change Grass Trimmer Line
To change grass trimmer line, first disconnect the spark plug on gas models or remove the battery on cordless models. Identify your head type (bump-feed, fixed-line, automatic, or pre-wound spool), press the tabs on the head to remove the spool cover, and pull out the old spool. Measure 15–25 feet of new line (or the length in your owner’s manual), wind it onto the spool in the direction shown by the arrow, thread the ends through the eyelets, and reinstall the head. Tug each line end to confirm it is secure, then test the feed mechanism before trimming.
Understanding the Trimmer Head: Why the Steps Differ by Design
Before you touch a single piece of line, it pays to know what kind of cutting head your trimmer uses. The four main designs are:
- Bump-feed heads: The most common type. You tap the bump knob on the ground while the head is spinning, and a spring mechanism releases more line automatically.
- Fixed-line heads: Also called manual-feed or fixed-head trimmers. The line is threaded through holes in the head and held in place; when the line wears down, you stop the machine and pull more line through manually.
- Automatic-feed heads: These use centrifugal force to feed line automatically as the engine or motor speeds up, with no bumping required.
- Pre-wound spools: A drop-in replacement spool that comes factory-loaded with line. You simply remove the old spool and snap in the new one, no winding required.
How Do I Know Which Trimmer Head Type My Trimmer Has?
Check the owner’s manual first, but you can usually tell by looking. A bump-feed head has a visible knob or button on the bottom of the head. A fixed-line head has visible line exiting through holes on the side with no knob underneath. An automatic head resembles a bump-feed head but has no bump knob. If you bought the trimmer used and have no manual, search the model number (printed on the housing) online to confirm the head design.
Which Trimmer Head Is Easiest for a Beginner to Reload?
Pre-wound spools are by far the easiest, since there is no measuring or winding. Bump-feed heads with replaceable spools are the next easiest, because you can wind the line onto the spool while it is out of the machine. Fixed-line heads require the most patience, since you must thread line through the head while it is still attached to the shaft.
Key Factors to Consider Before Changing Trimmer Line
How Do I Choose the Correct Trimmer Line Thickness (Gauge)?
Trimmer line is sold by diameter, usually from 0.065 inches up to 0.155 inches. Your trimmer head is rated for a specific range, and this is printed in the owner’s manual or stamped on the spool. Using line that is too thick can jam the feed mechanism or overload the engine; line that is too thin will break frequently and cut poorly. As a rule of thumb, electric trimmers typically use 0.065–0.080 inches, while gas trimmers use 0.080–0.110 inches or thicker for heavy-duty models.
Should I Use Round, Twisted, or Star-Shaped Trimmer Line?
- Round line: The standard, most affordable choice. It is quiet and works fine for light to medium grass.
- Twisted or square line: Provides a slightly more aggressive cut and is a good middle-ground option.
- Star-shaped or serrated line: Cuts through thick weeds faster and lasts longer, but it is noisier and can be harder on the trimmer head.
For most homeowners, a quality round line in the correct gauge is the right starting point. Upgrade to star-shaped line only if you regularly battle thick brush.
Do I Need to Buy a New Spool or Can I Reuse the Existing One?
You can almost always reuse the existing spool. Buy bulk line on a reel and wind it yourself, which is the cheapest option. Pre-wound spools are a convenience purchase for when you want to avoid winding entirely, but they cost more per reload. Only replace the spool itself if it is cracked, warped, or has a damaged feed mechanism.
How Much Trimmer Line Do I Need for One Full Spool Reload?
Most standard spools hold roughly 15–25 feet of line total, split between two line ends. A 100-foot reel of bulk line will therefore cover four to six reloads. Check your owner’s manual for the exact capacity, since larger heads on commercial trimmers can hold more.
What Tools Do I Need?
In most cases, you need no tools at all: just the new line, a pair of scissors or a utility knife to cut it, and gloves to protect your hands from the old line’s frayed ends. A few trimmer models require a screwdriver to remove the head cover, so keep one handy just in case.
Step-by-Step: How to Change Grass Trimmer Line
Step 1: Prepare the Trimmer Safely
Place the trimmer on a flat, stable surface. On gas models, disconnect the spark plug wire so the engine cannot accidentally start. On cordless models, remove the battery. On corded electric models, unplug the trimmer. This is non-negotiable: the cutting head can spin even when the trigger is not pressed if the mechanism is faulty.
Step 2: Remove the Spool and Cutting Head
Press the two tabs on the sides of the head cover and lift it off. On some models, you will instead turn the cover counterclockwise to release it. Pull the spool straight out of the head. Remove any leftover line and inspect the spool for cracks or wear. If the spool is damaged, replace it with an identical part number.
Step 3: Measure and Cut the Correct Length of Line
Cut two equal lengths of new line, each about 8–12 feet long for a standard double-line spool, or check your manual’s recommendation. If you are using a single-line spool, one longer piece is fine. Cutting both pieces before you start winding makes the job cleaner and prevents tangles.
Step 4: Wind the Line onto the Spool in the Correct Direction
Look for the arrow printed on the spool. It indicates the direction the line must be wound so that it feeds correctly when the head spins. Insert the midpoint of each line piece into the anchor slot or hole on the spool, then wind each end in the direction of the arrow. Keep the line taut and neat, with each wrap lying flat against the previous one. Leave about 4–6 inches of loose line at the end of each piece.
Step 5: Thread the Line Through the Eyelets
If your head has a single feed hole, thread both loose ends through that one eyelet. If it has two holes, thread one end through each. Pull the line ends until they just reach the cutting edge of the head. This length is ideal: too long and the engine will struggle; too short and the trimmer will not cut effectively.
Step 6: Reinstall the Spool and Cover
Align the spool with the drive mechanism inside the head and press it into place. Make sure the line exits through the eyelets and is not pinched between the spool and the housing. Replace the cover and press until the tabs click. On screw-type covers, turn clockwise until snug.
Step 7: Test the Feed Mechanism
Tug each line end to confirm it is locked in place. On a bump-feed model, hold the head off the ground, start the trimmer, and gently tap the bump knob on the ground once or twice. The line should advance a small amount. On a fixed-line model, pull the line manually to the correct length before starting. Trim a small test patch before tackling your full yard.
Adapting the Steps for Specific Spool Systems
How Do I Reload a Bump-Feed Trimmer Head?
Follow the standard steps above. The key detail is winding direction: bump-feed heads are sensitive to incorrectly wound line, which will cause the line to fuse or refuse to feed. Always wind in the direction of the arrow, and never overfill the spool, because a jammed spool is the most common cause of bump-feed failure.
How Do I Use a Pre-Wound Spool?
Remove the old spool, confirm the new spool’s line gauge matches your head’s rating, and drop it into place. Thread the loose ends through the eyelets exactly as you would with a hand-wound spool. Pre-wound spools are brand-specific in some cases, so verify compatibility before buying.
How Do I Change the Line on a Fixed-Head Trimmer?
Fixed-head trimmers do not use a removable spool. Instead, you cut a length of line (typically 10–15 feet), fold it in half, and push the folded end through the center hole in the head. Hook the loop over the notch inside, then pull both ends through the side eyelets. Pull the line tight so it seats in the internal channel, and trim the ends to the correct length. This method takes practice, so be patient.
Are the Steps Different for Electric, Battery, and Gas Trimmers?
The line-changing steps are identical across power types. The only difference is the safety preparation: unplug corded electric models, remove the battery on cordless models, and disconnect the spark plug on gas models. Gas trimmers also tend to use thicker line because they produce more power.
Troubleshooting Common Trimmer Line Problems
Why Does My Trimmer Line Keep Breaking After I Reload It?
The most common causes are using line that is too thin for the head, winding the line too loosely so it bunches, or hitting hard surfaces like concrete and stone. Check the recommended gauge for your model, rewind carefully, and keep the head just above the ground while trimming.
Why Won’t the Line Feed Out After I Wound the Spool?
This is almost always a winding direction problem. If the line is wound opposite to the arrow, it will bind instead of feed. It can also happen when the spool is overfilled or when the line ends are too short to reach the eyelets. Rewind the spool, leave longer loose ends, and make sure the line is not pinched under the cover.
What Should I Do If the Line Keeps Getting Tangled Inside the Head?
Tangling usually means the line was wound loosely or crossed over itself. Unwind the spool completely and start again, keeping firm tension on the line as you wind. Also check that the line gauge matches the head; oversized line can jam and twist inside the housing.
How Do I Know When the Line Should Be Replaced Rather Than Just Reloaded?
Replace the line when both ends are too short to extend past the cutting head, when the line has become brittle and snaps constantly, or when it has melted and fused together from overheating. If you are reloading more than once per mowing session, consider upgrading to a thicker gauge or a more durable line shape.
Frequently Asked Questions
How long should the line be when I load a new spool?
Leave about 4–6 inches of loose line on each end after winding. When you thread the ends through the eyelets, pull them out so they just reach the edge of the cutting head. Line that is much longer than the head will strain the engine and break quickly.
Can I use any brand of trimmer line in my trimmer?
Yes, trimmer line is largely universal as long as the diameter matches your head’s rated gauge. The spool itself may be brand-specific, but the line inside it is interchangeable. Check the owner’s manual for the recommended diameter range and buy any reputable brand within that range.
Why does my bump-feed head stop feeding line?
The usual culprits are line wound in the wrong direction, an overfilled spool, a worn or cracked spool, or debris packed inside the head. Disassemble the head, clean it, rewind the line correctly, and replace the spool if it shows damage.
Is it worth buying pre-wound spools instead of winding line myself?
Pre-wound spools are worth it if you value convenience and rarely want to handle line. They cost more per reload, but they eliminate measuring, winding, and most tangling issues. If you trim a large property frequently, buying bulk line and winding yourself is significantly cheaper.
Final Summary: The Fastest Safe Way to Change Trimmer Line
For a first-time user, the fastest safe method is to buy a pre-wound spool that matches your trimmer model. Disconnect the power source, pop off the head cover, swap the spools, thread the loose ends through the eyelets, and snap the cover back on. If you prefer to save money, wind bulk line yourself using the steps above, always following the arrow direction and keeping the line taut. Check your owner’s manual for the recommended line gauge and length, and if you no longer have the manual, search the model number online to find the manufacturer’s specifications.
