Quick answer

A nylon coil zipper that separates usually means the slider is worn or the coil teeth are misaligned. Try pinching the slider with pliers first; if that doesn't work, replace the slider or the entire zipper.

Why your nylon coil zipper keeps separating

Nylon coil zippers are flexible and smooth, but the slider can loosen over time. When the slider's channels spread apart, they no longer press the coil teeth together firmly, causing the zipper to open behind the slider as you pull it up. This is the most common reason a zipper won't stay closed.

Step-by-step repair for a separating zipper

First, check if the slider is the problem. With the zipper fully closed, gently squeeze the slider body with pliers—just enough to narrow the channel. Test the zipper. If it still separates, the slider may be too worn and needs replacement. For a YKK open-end zipper like the #5 nylon coil used in jackets and bags, you can often replace just the slider without removing the entire zipper.

When to replace the zipper instead

If the coil teeth are broken, missing, or the tape is frayed near the stop, repairing the slider won't help. In that case, install a new zipper. The YKK Open-End Zipper (#5 nylon coil, 55 cm) is a direct replacement for many jackets, duffel bags, and backpacks.

Diagnosis guide

  • Symptom: Zipper opens behind the slider as you pull it up.
  • Likely cause: Slider channels have widened from wear, losing grip on the coil teeth.
  • Corrective action: Pinch the slider gently with pliers. If that fails, replace the slider or the entire zipper. If the coil or tape is damaged, skip the slider fix and replace the zipper.

Product facts

  • YKK | Open-End Zipper | Nylon Coil | Purple | #5 | 21 3/4'' - 55 cm: YKK | Open-End Zipper | Nylon Coil | Purple | #5 | 21 3/4'' - 55 cm Separating (open-end) zipper One Way Separating Zipper Ideal for jackets, duffel bags, purses, backpacks and more... #5 Teeth For lightweight garments or flexible gear, choose a Nylon Coil Zipper. Its smooth, flexible coil design offers easy gliding and reliability for everyday use. If your old zipper's coil or tape is damaged, this YKK #5 nylon coil zipper is a direct replacement for many jackets and bags. The open-end design makes it easy to install.