As do most mechanical things, zippers break or wear out. If the zipper on your favorite men's dress pants no longer works properly, mend it or replace it yourself and save the money you would have spent on a tailor. A man's suit is a large investment, so don't let a balky zipper ruin your pants. All you need are some basic sewing supplies and maybe a new zipper.
Mend a Zipper
Assess the condition of the zipper to determine whether it can be mended or needs to be replaced.
Open the zipper. If the zipper is stuck and does not open easily, use needle-nose pliers or tweezers to get traction. If a zipper has been forced and does not easily work again, replace it. If the zipper is still intact and works, but some stitches holding the zipper in place have come loose, pin the zipper back into place with straight pins.
Stitch carefully with a sewing machine along the previous seam holding in the zipper. You can also sew it with small stitches by hand, but the stitching won't look as good as when done by machine. Fortunately, the zipper is hidden in men's dress pants, lying under the flap, or fly. Whether you sew by machine or hand, snip off excess thread. If a zipper is wearing out or has broken teeth, replace it.
Replace a Zipper
Measure the old zipper and buy a new one of the same length and color. Note how the old zipper was sewn into place before you begin sewing in the new zipper.
Remove the old zipper. Use a seam ripper to open the stitching holding the broken zipper. Snip off and dispose of the old thread.
Open the new zipper and pin it into place or baste it down its whole length. Cut off the top material above the new zipper or open the material in the pants to slide it into place. Try the zipper to be sure it works properly before you do any sewing.
Sew down the new zipper with your sewing machine. A man’s dress pants zipper has a flap covering the zipper that should not show any stitches on the outer side. Open the seam to the left of the zipper teeth under the flap to release the seam’s material so you can sew down the zipper on that side. Restitch this seam after the zipper is in place, or sew it with a needle if you prefer.
Sew down the other side of the zipper across from the flap. Don’t overlap any material around the zipper that could get caught in the teeth. Leave enough room so the zipper can be easily zipped and unzipped. Snip off any loose threads.