Strimmer Line Keeps Breaking or Won't Feed? Every Cause & Fix (UK Guide)

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Strimmer Line Keeps Breaking or Won't Feed? Every Cause & Fix (UK Guide)

By Jim Fellows, Garden Machinery Specialist · Updated 23 July 2026 · 9 min read

No garden tool burns through consumables like a strimmer, and no consumable causes more swearing than trimmer line. But here's the thing the frustration hides: line problems are nearly always caused by the line, the winding or the technique — not the machine. Which means every fix below is cheap, and most are free.

Find your symptom, then jump to the fix.

Fast Diagnosis: Symptom → Likely Cause

Fix 1: Brittle line — the overnight soak

Nylon line is manufactured with a small moisture content that keeps it flexible. Leave a spool in a hot shed for a season or two and it dries out, turning tough monofilament into dry spaghetti that shatters on the first dandelion. The classic professional fix costs nothing: soak the spool in a bucket of water overnight before use, and store line somewhere cool and dark rather than on a sunny shelf. If line snaps into short pieces when you flex it sharply in your hands, it's past saving — replace it. Line is cheap; buy fresh strimmer line in a diameter your head accepts rather than nursing a stale roll.

Fix 2: Snapping at the head — edges, and worn eyelets

Line that breaks right at the exit hole and retreats into the spool is telling you where it's being damaged. The usual cause is contact with hard surfaces: every time the line slaps a wall, fence post, kerb or metal edging, it takes a nick, and nicked line snaps at the nick. Adjust your approach — let the last centimetre of line tip do the work near hard edges rather than burying the full line depth against them. Also inspect the head's metal or plastic eyelets where the line exits: after years of use they wear sharp grooves that cut the line themselves. Worn eyelets (or a cracked, tired head) are the signal to fit a replacement trimmer head matched to your machine.

Fix 3: Won't feed — rewind the spool properly

Bump-feed heads release line by centrifugal force when you tap the head down — and they can only release line that's wound to run free. Open the head (usually a quarter-turn or two tabs), lift the spool, and rewind: follow the direction arrow moulded on the spool, wind in neat, parallel coils under light, even tension — snug, never strained — keep twin lines in their separate channels without crossing, leave the specified tail lengths, and park the ends in the spool's retaining notches while you reassemble. Nine out of ten feed failures are crossed or over-tight coils jamming under load; a five-minute careful rewind cures them. Also check the line isn't simply too short to feed — most heads can't self-feed from a stub, so pull it through by hand to the working length first. If rewinding bores you, pre-wound replacement spools for your model turn the job into a cassette swap.

Fix 4: Line fused to itself

Pull the spool out and find the coils melted into one solid lump? That's heat fusion: sustained aggressive cutting — long grass, brambles, full line depth — heats the head enough to weld the nylon layers together, and the next bump-feed pulls against a solid block. Cut the fused section away and rewind (or fit a fresh spool), then treat the cause: take heavy growth in stages with the line tip, pause on long runs to let the head cool, and consider a higher-quality line — bargain-bin nylon fuses at lower temperatures than decent branded line. A splash of the water-soak habit from Fix 1 helps here too, since dry line fuses more readily.

Fix 5: Line vanishing fast — match line to job (or admit it's a blade job)

Line diameter is a trade-off between cutting power and what your machine can spin: light cordless trimmers typically run around 1.6mm, general-purpose machines around 2.0mm, and petrol brushcutters 2.4mm and up — your manual states the maximum, and fitting thicker line than the head is rated for overloads the motor. Shape matters too: round line is the most durable and forgiving; square and star profiles cut cleaner but wear faster; twisted line runs quieter. If you're feeding line into brambles, nettle jungles or woody stems and watching it evaporate, the honest answer is that no line wants that job — it's brushcutter blade territory. Our multi-tool guide covers the brushcutter attachment that eats what line can't.

Fix 6: Technique — the tip does the cutting

A strimmer cuts with the last couple of centimetres of line tip travelling at maximum speed — not the whole line length. Sweep steadily so the tip slices, overlap passes slightly, tilt the head a few degrees for edging, and work long grass top-down in layers instead of ploughing in at ground level. Bury the full line in thick growth and you get everything on this page at once: wrapped grass, stalled cutting, overheating, fusion and snapped line. Slow is smooth, and smooth is — genuinely — faster by the end of the lawn.

Prevention: The Two-Minute Line Routine

Buy decent line in the right diameter, store it cool and dark, soak older spools overnight before a big session, rewind with care, and let the tip do the work. Do that and a roll of line lasts a season instead of a fortnight — and the strimmer goes back to being the five-minute finishing tool it's meant to be. We'll dig into which specific lines are worth buying in a dedicated line buying guide later in this series.

Frequently Asked Questions

Why does my strimmer line keep breaking?

Usually one of three things: the line has dried out and gone brittle in storage, it's too thin for what you're cutting, or it's repeatedly striking walls, fences and edging that nick it. Fresh line of the right diameter, an overnight soak for older spools, and tip-cutting near hard edges cure most cases.

Does soaking strimmer line in water really work?

Yes — it's a long-standing trade practice. Nylon line relies on a small moisture content for flexibility, and storage slowly dries it out. An overnight soak restores suppleness and noticeably reduces snapping. It won't resurrect line that's fully perished, but it extends the life of everything in between.

Why won't my strimmer feed line when I bump it?

Almost always the winding: crossed coils, over-tight winding, or line fused together by heat jams the spool so the bump mechanism can't release it. Rewind in neat parallel coils following the spool's direction arrow, keep twin lines in their own channels, and make sure enough line protrudes to feed from.

What size strimmer line do I need?

Whatever your machine's manual specifies — as a rule of thumb, around 1.6mm for light cordless trimmers, 2.0mm for general-purpose machines, and 2.4mm-plus for petrol brushcutters. Thicker isn't better if the head and motor aren't rated for it.

Is round or shaped strimmer line better?

Round line is the most durable and the best default for general grass. Square and star-profile lines cut cleaner with their edges but wear and snap faster, especially around hard surfaces. Twisted lines trade a little durability for quieter running. For most gardens: round for the boundaries, shaped if you prize a crisp finish on open grass.

Garden Review is reader-supported. As an Amazon Associate we earn from qualifying purchases made through links on this page, at no extra cost to you. This does not influence our advice. Always follow your machine's manual and safety instructions, and wear eye protection when strimming.