A weed eater, also known as string trimmers, weed trimmers, or weed whackers, spins a nylon string at high speeds to cut grass and weeds. When the line wears down, you’ll need to reload it. We’ll explain how to put string in a weed eater in 10 easy steps.
If you’d rather skip the hassle entirely, Lawn Love’s lawn mowing service includes weed eating and edging — just schedule a pro and skip the spool.
| Key takeaways |
|---|
| • Match string size and gauge to your trimmer model as the wrong size can jam or break it. • You’ll need 10–20 feet of line per load; check your manual for the exact amount. • Wind the string in the direction of the arrows or it won’t feed. • Speed feed and auto-feed trimmers require less disassembly. |
- Trimmer head type comparison
- 10 steps to restring weed eaters
- 1. Choose the correct replacement string
- 2. Measure your string
- 3. Turn off and clean your weed eater
- 4. Remove the cap and take out the spool
- 5. Remove any old string
- 6. Attach the new string
- 7. Wind up the string
- 8. Feed the string through the external holes
- 9. Reassemble the weed eater
- 10. Pull out the desired length of string
- FAQs
Trimmer head type comparison
Before you begin, you need to know what type of trimmer head you are working with.
| Head type | How to reload | Best feature |
| Bump feed | Requires removing the spool, manually winding the string, and reassembling | Gives you manual control over when line advances |
| Auto-feed | Requires buying a pre-wound replacement spool that simply drops in | No winding required; easiest to change |
| Speed feed | Thread the line straight through the eyelets and twist the exterior cap to wind it | No disassembly required; fastest to reload |
Pro tip: “If reloading traditional bump-feed heads is frustrating, a speed-feed head can save you time,” says Taylor Olberding, franchise owner at Heroes Lawn Care, in Omaha, NE. “It lets you reload the line quickly without opening the spool. But remember, it’s not completely maintenance-free. It still needs occasional cleaning.”
10 steps to restring weed eaters
Your weed eater’s manual should have specific instructions for your make and model. However, user manuals are easy to lose and aren’t always clear.
These 10 steps should work for most models. We’ll cover any variations you may encounter and how you can adjust the steps based on the type of weed eater.
1. Choose the correct replacement string
Weed whacker strings (trimmer line) differ in size, shape, and model. Here are the key features you need to consider:
- Size: The size or gauge of a string is usually non-negotiable. Check the manual to see what size you need.
What happens if you use the wrong size trimmer line? A string that’s too big can get stuck, and a string that’s too small is more likely to break.
Trimmer line size guide
| Size (gauge) | Best for | Trimmer type |
| .065″ – .080″ | Light residential work, grass, and thin weeds | Light-duty electric/battery trimmers |
| .085″ – .105″ | Medium to heavy residential, thick weeds, light brush | Standard gas-powered trimmers |
| .110″ and up | Commercial landscaping, heavy brush, thick stalks | Professional heavy-duty trimmers |
- Shape: Olberding explains that the shape of the trimmer line matters depending on your yard conditions. “Round line works well for everyday trimming and edging around lawns and walkways,” he says.
“Twisted or spiral line can cut dense grass more efficiently and runs a little quieter. Square or star-shaped line is better for thicker weeds or light brush because the edges cut more aggressively, although it can wear faster and produce more noise,” Olberding says.
- Model: Whether you have gas-powered or battery-powered weed eaters, the brand dictates which size is suitable for your machine. However, generic brands also can work if they’re the correct size.
Note: If you have an auto-feed string trimmer, look for a spool replacement instead of just a roll of string.
2. Measure your string
You generally need 10 to 20 feet of trimmer line, but it would depend on your weed eater’s design and spool size. Check your user manual for the exact measurements for your model.
Models with two strings can either use one long string threaded through or two strings that will wind around the spool next to each other.
Pro tip: Use your arm span to estimate length quickly. Arms stretched wide are roughly 5 feet. Two arm-spans = 10 feet, four = 20 feet.
3. Turn off and clean your weed eater
It’s unsafe to change the string trimmer line while your weed eater has power. Always unplug the battery or turn the gas engine completely off before you touch the cutting head.
4. Remove the cap and take out the spool
The string wraps around a spool inside the weed eater’s head. Look for arrows that indicate which direction to turn it or how to line up the lid for removal. Some string trimmer heads have buttons or tabs you need to push inward. When the cap is off, pull out the spool.
Watch out for any springs — some are attached, but others are loose and could get lost. If it’s loose, set it aside.
Note: Some speed feed trimmers don’t need to be disassembled. Thread the string through the eyelets (line up the arrow or line with the eyelets) and skip to Step 6.
5. Remove any old string
Once you take out the spool, remove the old line. Pay attention to where the string is attached and which way it winds around the spool. You can take a picture to help you remember.
If you have an auto-feed weed eater, you will need to replace the whole spool rather than just the string. Don’t worry about attaching the string or winding it up — skip to Step 8.
No string? No worries. Just move on to Step 6.
Note: In some cases, your weed eater may still have enough string, but it’s tangled or damaged. You should replace damaged string, but you may be able to untangle and use undamaged string. Follow Steps 6 and 7 to ensure it’s properly attached and wound up.
6. Attach the new string
Depending on the type of weed eater you have, the string trimmer lines may attach differently. For most models, you’ll need to locate the hole or notch in the spool. Then, insert one end of the string so it stays secure. Do this for however many strings your weed eater has.
If you have a speed feed trimmer, thread the line through one eyelet and out the other until it’s even on both sides.
7. Wind up the string
Once you’ve attached the string, follow the direction of the arrows stamped on the spool to wind up the line.
Olberding says that this step is where the most errors happen. “When it comes to putting string in a weed eater, problems usually happen because of how the line is wound on the spool,” he explains. “The most common mistakes we see are winding the line in the wrong direction, overlapping the coils, or packing the spool too tightly. This can cause the line to refuse to feed when you bump the head.”
Wind it up tightly in neat, parallel rows so it fits properly and doesn’t unravel. Remember to leave at least 4 to 6 inches of string unwound at the end. Weed eaters with multiple strings usually have a divider in the middle of the spool. Keep each string in its respective channel so they don’t get tangled.
For speed feed trimmers, you’ll need to rotate the trimmer head to wind it up.
8. Feed the string through the external holes
When your spool is wound tight, hold the string in place with your thumb. Thread the loose ends of the string through the eyelet holes on the outside cover of the weed eater head, then pop the spool back inside.
Skip this step if you have a speed feed trimmer — you already threaded the eyelets before winding.
9. Reassemble the weed eater
Place the spool back in, reposition the spring if it came out, then snap or twist the cap back on until it clicks securely. Give the strings a quick tug to ensure they slide smoothly through the eyelets.
Note: Speed feed trimmers require no reassembly since you don’t need to take them apart.
10. Pull out the desired length of string
Depending on your trimmer type:
- Bump feed: Turn the machine on and tap the head on the ground to release more line
- Auto-feed: The trimmer dispenses the right amount automatically when powered on
- Button feed: Press the manual button on the head and pull the line
Note: If there’s too much string or the new lines aren’t the same length, you can trim them down as needed.
Read more: How to Edge Your Lawn
FAQs
The most common cause is hitting hard surfaces (rocks, fences, concrete). Olberding says other causes include “using the wrong diameter line, brittle or low-quality string, or failing to clean dirt from the spool and head can also create frequent feeding issues.”
You should replace the string if there’s none left, it won’t come out, it gets caught, or it tangles easily.
It depends on how frequently you use your weed eater. Most people need to change their weed eater string every 3 months. You might have to replace the string daily if you use your weed whacker every day. But if you use it sparingly, you may need to change it only once a year.
Of course, the most straightforward rule of thumb is to replace the string whenever it has run out or you have issues.
“As for soaking nylon trimmer line in water, there is some truth behind it,” explains Olberding. “Nylon absorbs a small amount of moisture, which helps keep the line flexible if it has become dry or brittle over time. However, it’s not a magic fix. If you’re using fresh, good-quality line that’s been stored properly, soaking it usually isn’t necessary.”
Read more: How to Weed Eat Your Lawn Like a Pro
Cut yourself some slack and call a lawn care pro
Even if you know how to restring your weed eater, you may not want to do it yourself. After all, who wants to spend their weekend whacking weeds when they can relax? Contact a local Lawn Love lawn care pro, and you won’t have to worry about weed whacking, mowing, or edging.
Main Image: A man holds up a grass-covered string trimmer after yard work. Photo Credit: Анастасия Бурлакова / Adobe Stock
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