By ShowMeStepByStepPublished Updated
Based on a video by UCAN Zippers USA.
Most "broken" zippers are not broken. The teeth are fine and the tape is fine. What has gone wrong is the slider, the little metal or plastic housing that pulls the two rows of teeth together. Sliders wear, spring open a fraction, and stop pinching the chain. Everything below follows from that.
Hyrum of UCAN Zippers USA runs a zipper company and his fix takes a pair of needle nose pliers and about ten minutes. He is candid that it is a get-it-working repair rather than a forever one. On a backpack, a duffel or a work jacket, that is exactly what you want. On a coat you love, or a slider whose metal has gone soft with age, replace the slider outright.
Match the symptom first. Each one below has its own fix.
This is the most common failure on jackets and bags, and it is the one the video walks through. With the slider pulled clear, one row of teeth sits outside the slider. Ease the slider open a fraction more with the pliers, angle it so the empty channel lines up with the loose chain, and work the teeth in a few at a time. Once both rows are inside, pinch the top and bottom of the slider back together and run it end to end to test.
If the zipper closes and then pops open behind the slider, nothing has come off. The slider has simply worn until it no longer squeezes the two rows together. You do not need to feed anything back in. Run the slider to the bottom, hold it flat, and squeeze the top plate and bottom plate toward each other with the pliers, one side at a time. Squeeze gently and test. If it still gapes, squeeze a little more. Too much and the slider will jam.
On a coil zipper, the nylon kind on most bags, this fix lasts months. On a metal-tooth zipper it can last years.
If the slider has come off the end entirely, it goes back on from the bottom on a jacket and from either end on a bag.
If the old slider is cracked or the pull is gone, this is the moment to swap it. Match the number stamped on the back of the old slider, usually 3, 5, 8 or 10, and buy that size.
A stuck zipper almost always has fabric or a loose thread caught in the slider. Pulling harder makes it worse. Back the slider off the way it came, easing the trapped fabric out with your fingers. If it will not move at all, rub the teeth on both sides with a graphite pencil, a bar of soap or a candle. That lubricates the chain enough to free the slider. Then trim the loose thread so it cannot catch again.
Backpack zippers fail the same way as jacket zippers, but they are usually two-slider zippers, one from each end. Fix one slider at a time. If you replace one, the two sliders face each other on the chain, nose to nose. Jacket zippers are the separating kind with a pin and box at the bottom. The slider sits on one side when open, and the fix is the same, but the slider only comes off the pin side.
Missing teeth on a metal zipper, or a coil zipper whose coils have pulled away from the tape, cannot be fixed with pliers. That is a sewing job: unpick the old zipper and stitch in a new one. It is worth doing on a good coat. On a cheap bag it is usually not.
Sewing a zipper into a garment from scratch is its own project, and it is covered at how to sew a zipper.
8 steps · about 10 minutes.Check off each step as you go and your progress saves automatically.
Look at the zipper with the slider pulled clear. On a chain that has come off one side, the teeth on that side will be sitting outside the slider rather than running through it.
Check the slider itself from the side. If the top and bottom plates have spread apart, that gap is the actual fault, not the teeth.
Tip
Zip it up and watch where it separates. If it comes apart right behind the slider every time, the slider is the problem. Watch this step
You need a pair of needle nose pliers and, if you are replacing rather than reusing, a slider that matches your zipper size and a new bottom stop.
Zipper sliders are sized. A number 5 slider will not run on a number 3 chain, and the size is usually stamped on the back of the old slider.
Tip
Buy a mixed slider kit rather than one slider. The size stamped on the old one is often worn off by the time it fails. Watch this step
The slider has already sprung open, which is why the zipper failed. Ease it open a little further with the pliers so there is room to get the chain back inside.
Go gently. On an older bag the metal has fatigued, and it will snap if you lever it hard.
Tip
Think of the slider as a clamshell. You are hinging it open a millimetre or two, not prising the two halves apart. Watch this step
Angle the slider so one channel lines up with the end of the chain, and work the teeth in a few at a time.
The tape wants to fold. Keeping it flat and pulling from beyond the slider rather than pushing at it makes the teeth track properly.
Tip
If it will not start, the slider is not open enough. Go back a step rather than forcing the teeth. Watch this step
Now do the same on the other channel. This is the fiddly one, because the first side is already in and gets in the way.
Hold the slider still and bring the chain to it. Moving the slider along the chain you have already threaded will just pull the first side back out.
Tip
Pliers give you a better grip on the tape end than fingers do, and let you keep the tape flat while you feed it. Watch this step
With both sides through, check the chain is even. If one side is puckered or sitting higher than the other, hold the slider and pull the tape until the teeth line up level.
Then run the slider all the way to the closed end before you do anything else. Pinching it shut halfway along leaves you with a zipper that only works from the middle.
Tip
On a bag, work out which end is the closed end before you start. Getting this backwards means undoing the whole repair. Watch this step
Take the needle nose pliers and squeeze the top and bottom of the slider back towards each other. That closes the clamshell gap that caused the failure.
Small squeezes, testing as you go. Overtighten it and the slider will seize solid on the chain.
Tip
Squeeze the sides of the slider body, not the pull tab. The tab bends easily and does nothing for the repair. Watch this step
Run the slider from one end to the other a few times. It should close the teeth cleanly behind it and not separate.
If the zipper still pops open, the slider needs another small pinch. If it now sticks or drags, you have gone slightly too far and need to ease it back open a fraction.
Tip
Add or crimp a bottom stop if the old one is missing, otherwise the slider will run straight off the end again. Watch this step
Keep going
How to Clean an Oven
How to Fix a Zipper That Came Off the Track
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5 questions covering what you just read. No signup, no score saved, and you can stop after this one.
Question 1 of 5
A zipper keeps separating behind the slider as you close it. What has usually gone wrong?
Quick reference
5 questions, answers, and one-line explanations. Tap to expand.
1.A zipper keeps separating behind the slider as you close it. What has usually gone wrong?
Answer: The slider has sprung open slightly
The slider is a clamshell, and once it spreads the teeth stop locking behind it.
2.Which tool does this repair actually need?
Answer: Needle nose pliers
Pliers both open the slider to feed the chain in and pinch it shut again.
3.Why will a number 5 slider not run on a number 3 chain?
Answer: Sliders are sized and must match the chain
The size is usually stamped on the back of the old slider.
4.Once both sides of the chain are threaded, what do you do before pinching the slider shut?
Answer: Run it down to the closed end
Pinching it shut halfway along leaves a zipper that only works from the middle.
5.You pinch the slider closed and now it drags and sticks on the chain. What does that tell you?
Answer: You squeezed it slightly too far
Ease it back open a fraction, because overtightening seizes the slider solid.
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