Quick answer: If a zipper closes and then splits open again behind the slider, the slider has often widened slightly. A careful squeeze with pliers can restore its grip in under a minute.
How to fix a zipper that keeps splitting
- Move the slider down as far as it will go.
- Use ordinary pliers to squeeze one side of the slider very gently.
- Squeeze the other side by the same small amount.
- Test the zipper. Repeat with slightly more pressure if needed.
Go gently. If you squeeze too hard, the slider can become difficult to move. Small adjustments are better than one hard squeeze.
Why does this work?
Our fleece jacket had the classic problem: the zipper appeared to close, but the teeth separated again immediately behind the slider. The teeth themselves were intact.
With use, a metal zipper slider can spread slightly. It then stops pressing the two rows of teeth together firmly enough. Gently narrowing the slider can restore that pressure.
I have used the same trick on jackets, jeans, hoodies and even a tent.
When this trick will not help
This works when the teeth are intact and the problem is a worn or slightly widened slider. It will not repair missing teeth, torn zipper tape or a cracked slider.
If the slider itself is damaged, a replacement slider can sometimes be fitted without replacing the entire zipper.