How to replace strimmer line

Inspired by a clear UK tool guide. This walk-through draws on the video "How To Replace Your Spool Line - Grass Trimmer" from the WORX UK channel, which covers both single and dual-line spools in a straightforward, no-nonsense format. While the video focuses on WORX models, the principles apply to most common UK strimmer brands including Stihl, Ryobi, Black & Decker, and Bosch. Well worth watching alongside this guide.

1. Switch off and make the strimmer safe

For electric models, unplug from the mains. For cordless, remove the battery pack. For petrol, turn the ignition switch off and disconnect the spark plug lead. Never work on a spool with the power connected - the bump-feed head can release line unexpectedly if it contacts a surface.

Let any recently-run petrol strimmer cool for a few minutes before you handle the head. The area around the cutting head gets warm during use.

2. Identify your spool type

There are three common configurations. A single-line spool has one cutting line emerging from the head. A dual-line spool has two lines emerging at 180 degrees to each other. A rapid-load or speed-feed head takes pre-cut lengths rather than a wound spool. Check which you have before buying replacement line, and match the line diameter - common sizes are 1.5mm, 1.6mm, and 2.0mm for domestic strimmers.

Thicker line cuts heavier growth more effectively but wears the motor harder on smaller tools. Use the diameter specified in your manual.

3. Remove the spool cap

Press the tabs on either side of the spool cap simultaneously and pull or rotate it away from the head. On some models you twist anti-clockwise; on others it simply pops off. There is usually a retaining spring inside - have your hand ready to catch it as the cap comes away, because the spring has a habit of launching itself across the garden.

Lift out the old spool and clean any grass clippings or dirt from the inside of the head. Packed debris is one of the most common reasons line jams mid-use.

4. Wind the new line onto the spool

Cut a length of new line - typically 5 to 9 metres per side depending on the spool size (check the spool body for the recommended length stamped on it). Fold the line in half to find the centre, hook the centre loop into the small slot on the spool divider, and wind both halves simultaneously in the direction of the arrows moulded into the spool body.

Wind evenly and keep tension on the line as you go. Loose or crossed wraps jam in the head and cause frustrating stops. Leave the last 15–20cm free on each side and feed the ends through the exit eyelets on the spool to hold them in place temporarily.

5. Reassemble and feed the line through the head

Drop the loaded spool back into the head and ensure the two line ends are fed out through the correct guide holes in the head housing. Press the spring back in if it came out, then refit the cap - align it, press down, and twist or click until it locks. Pull each line end out a few centimetres to confirm it is free and not trapped under the cap.

Give the bump-knob on the base of the head a test tap on a hard surface and see if the line advances. If it does, you have it right. If not, remove the cap and check the winding direction - it must match the arrow on the spool body.

6. Test cut and trim to working length

Reconnect power and run the strimmer briefly over grass. The cutting blade or guard on the head will automatically trim the line to the correct working length as it contacts it. If the line is too long before it reaches the guard, the strimmer head will vibrate noticeably - the guard will sort it out within a few seconds of use.

That said, if the line seems very long after reassembly, switching off and trimming it manually with scissors to about 15cm first is perfectly reasonable and saves the motor working harder than it needs to.

When to call a handyman

Strimmer line is firmly a DIY job. But if the head is cracked, the bump-feed mechanism is broken, or a petrol model has lost compression or will not start, those are separate repair jobs. Richard can help with general garden tool maintenance as part of a gardening visit if needed.