The 10 Most Common Reasons Why Your Strimmer Line Keeps Breaking

If you’re into garden maintenance, no doubt you own a grass trimmer. They’re easily one of the best tools for achieving tidy edges and borders. 

But strimmer line that keeps breaking is hugely frustrating, and it’s an issue that can make a simple job take much longer than necessary. We’ve researched the most common things that cause strimmer line to break, to help you troubleshoot the problem. 

Check out these 10 reasons why your strimmer line keeps breaking (and how to fix the problem).  

1. It’s Coming into Contact with Hard Obstacles


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The most common cause for strimmer line to break: contact with a hard object. This could be a wall, paving edge or even a large stone. 

To avoid this, take extra care where you’re using the strimmer. Inspect the area before using your grass trimmer, removing any large stones or debris. Take note of any hard surfaces that your strimmer could make contact with and do your best to avoid these. 

2. You’re Using Low-Quality Line

You tend to get what you pay for when it comes to nylon line. If your line is cheap and poor quality, you may find it breaks more easily than high-quality trimmer line. 

Cheap nylon line will be mixed with materials that make it weaker, meaning the line breaks faster than it should. 

The strongest trimmer line is round, and it should be pre-rolled on an attachable reel. Rolling the line yourself can cause damage, which is why pre-rolled is best. 

You know what I’m going to suggest as a solution to this problem: don’t scrimp when it comes to cutting line. Buy from respectable retailers and brands.

3. The Line is Incompatible with the Strimmer


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If you are using good quality trimmer line and avoiding hard objects, you might be using line that is incompatible with your strimmer.

This might be because it’s too thick, too thin, the wrong shape, or simply the wrong brand. 

Trimmer line is usually either round, square, or star shaped. A strimmer designed for round trimmer line may not accommodate square trimmer line and vise versa. 

Check back with the manufacturer’s instructions to see what thickness, shape and brand of line you need. 

4. The Line is Too Thin for the Job

Depending on the thickness of the grass or weeds you are cutting, you might be using strimmer line which is too thin for the job. If you’re trying to cut grass that is dense, or approach thicker shrubs, the line can break easily if it’s too thin. 

There are many different thicknesses of line on the market. The most common options are 1.5 mm, 1.6 mm, 2.4 mm and 3 mm. Thinner line is best for simple grass cutting – the instructions of your strimmer will state what thickness of line you need. 

The thickness of the line you need will also depend on what you are doing. For tougher jobs, you’ll need thicker line; however, you’ll also need more power to drive thick line. For this reason, strimmers with less power may not be compatible with thicker line.

5. The Line is Wound Incorrectly

The reason your strimmer wire keeps breaking could be as simple as it not being wound on correctly. Try to look for pre-rolled line that comes on an attachable reel. 

If your line isn’t wound around the reel correctly, it may not dispense properly. Any snags can cause the line to break. 

To properly roll your trimmer line you should: 

1. Turn off your trimmer
2. Detach the spool from the trimmer head
3. Pull off around 6 meters of line from the reel
4. Take one end of the line and thread it through the hole in the middle of the spool
5. Pull the line through until you reach the middle – so you have two lines the same length
6. Take each end and wind around the spool at the same time
7. When there’s around 20 cm left on each, feed both ends through the holes at the side of the trimmer head, then reattach the trimmer head

When winding the line, try to prevent the lines from crossing as much as possible. If the line is crossing over itself, there’s a higher risk of it becoming caught down the line. 

6. There’s Debris in the Strimmer Head


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Your trimmer line may be breaking because there is debris in the strimmer head. Clean strimmers will perform much better than those covered in mud or grass. 

Debris in the cutting head will disrupt the tension of the line. After use, it’s recommended that you clean off any grease, dirt and debris from your strimmer. Use a combination of water and dish detergent, or use a stiff brush to remove any stubborn, dry dirt. 

Use a soft brush or vacuum to clear any blockages from around the ventilation slots. A poorly ventilated motor can overheat and cut out.

7. You’re Using Too Much Line (Or Too Little) 


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If you have excess line, it’ll break more often. This is partly because you have less control over what long line comes into contact with, so you’ll find it begins to hit unforgiving objects like walls, causing it to snap. 

You may also be using a line that’s too short. Lines which are too short are equally likely to break. The cord has to spin with enough centrifugal force to cut the grass. The spinning power won’t exceed the grass’s strength if the line is too short. The grass will slice the line, instead of the other way around. 

Keep your trimmer line at a consistent 20 cm long – this is the optimum length to prevent breakages! 

8. You’ve Replaced a Part & it’s Incompatible


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One common reason why trimmer line keeps breaking is that a replaced part is incompatible with the strimmer you are using. If you’ve recently fixed the strimmer or replaced a part such as the cutting head, you may have used the wrong part, which will stop your strimmer from working properly.  

Manufacturers provide very specific instructions with their strimmers, and using the wrong part or line can cause it to break. 

If you are replacing a part of your strimmer, ensure it’s either designed by your original manufacturer, or compatible with the strimmer you’re using. 

9. You’re Asking Too Much From the Strimmer

Not all grass trimmers are made equally. While some grass trimmers (like petrol models) have enough power for very tough jobs, others are designed for light-duty work. If you’re trying to use your small cordless strimmer as a brush cutter, it’s no wonder that it’s starting to break! 

If you’re tackling grass or weeds that are too dense for your strimmer, your line is going to snap more easily. Ensure your strimmer has enough power for what you are asking it to do. 

10. The Strimmer Line is Old

Strimmer line is made from nylon and it will dry out over time. This is because nylon is porous, and it becomes brittle when moisture evaporates. Old, brittle line snaps much easier than new line. 

Nylon line will dry out whether you are using it regularly or not. If you leave your strimmer in storage for months at a time, the nylon line will still dry out. Any spools of line that you have bought could also dry out, even if they’re not fixed onto the strimmer yet. It’s therefore not a great idea to buy line in advance.

If the grass strimmer line is still relatively new, you can soak it in water the night before you intend to use it. This will make it less brittle. Another option is to store it in a bucket of water when not in use. 


Why does my trimmer line keep breaking? 

The most common reasons why your grass trimmer line keeps breaking are: 

  • The line is poor quality – replace it with a better quality line
  • The line is old and has become brittle – buy some new line
  • You are coming into contact with a hard surfaces when you’re strimming, such as a wall, paving edge or large rock
  • The line is not compatible with your trimmer
  • The line hasn’t been rolled properly – try to purchase a line that is pre-rolled

How long should strimmer line last? 

If used weekly, your strimmer line should last between three and six months. While higher quality lines will last longer than poor quality line, you should ensure you’re not overloading your strimmer to prevent it wearing down too quickly.

One way to elongate the lifespan of your strimmer line is to soak it in water. Strimmer line dries out over time and becomes brittle, which can lead to it breaking more easily. Storing or soaking your line in water will make the line more flexible and prevent it from drying out. 

Should I be using square or round strimmer line? 

As square line has four sharp edges, it’s a good option for large swathes of grass and weeds. Generally, square line cuts faster and cleaner. 

If square strimmer line collides with rocks and hard objects however, it’s far more likely to break than round line. 

The strongest strimmer line to use is round, followed by star and finally square. Square cut line is the weakest, although some grass trimmers will only be compatible with this type of line. 

Round line is a lot stronger, especially if your strimmer comes into contact with hard surfaces. Round lines are also easier to fit than square lines, and they tend to be more affordable. 

The downside to round line is that it doesn’t cut as well as square, occasionally ripping the grass as opposed to cleanly cutting it.

Should I just buy thicker line to stop it from breaking so much?

Although using thicker trimmer line could solve your problem, there are some cases when using thick line isn’t the right approach.

For example, if you are using a reasonably lightweight trimmer (e.g., a model that is battery powered) it probably won’t cope very well with thick line. The grass trimmer also needs to have enough power to spin the and create enough centrifugal force to cut the grass. If the line is too thick and heavy, lightweight strimmers will struggle to cut properly which won’t solve the problem.

Before opting for thick line, make sure that the brand and model of your strimmer is compatible with it.