A leaky water key can make playing difficult and a horn sound strange. Instrument repair professionals can fix leaky water keys, but often times all a water key needs is a new cork—an easy fix you can do at home. Water key corks are inexpensive and available at most music stores and online, but a wine cork cut to the right size will work in a pinch.

Obtain a replacement water key cork.
  • Obtain a replacement water key cork.

    • If you’re in a rush and don’t have a replacement cork, you can make a temporary one out of a wine bottle cork.

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Remove the old cork.
  • Remove the old cork.

    • Insert a sharp tool, such as one tine of a pair of tweezers or needle-nose forceps, between the cork and the metal edge.

    • Pry up the cork using the metal edge for leverage.

    • Repeat this at several points around the cork until the cork comes free.

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  • If you have a replacement cork, skip to Step 10.

  • If you’re using a wine bottle cork to make a replacement cork, place the cork on its side and measure 3 mm from the cork edge. Mark this point.

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  • Using a serrated knife (such as a steak knife), cut the cork horizontally along your mark.

    • Cutting corks can be tricky. Make sure to keep fingers out of your knife's way.

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  • Using a ruler, measure the diameter of the water key slot you removed the cork from in Step 2.

    • Measure from inside edge to inside edge.

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  • Place the 3mm slice you cut from the wine cork flat on a surface.

  • Mark a point in the center.

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  • Using a ruler, measure half the diameter from Step 5 above and below the center mark.

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  • Rotate the ruler 90 degrees and repeat Step 7.

    • Your cork slice should now have four marks equidistant from the center mark.

  • Draw a circle connecting the four marks around the center.

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  • Using your knife, cut out this circle.

    • It helps to slice edges off at angles, one at a time.

    • This might take a few tries, so if you end up with a non-round circle cut out, repeat Steps 3-9 with the remaining wine cork.

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  • Dry fit the new cork in the water key slot to make sure it is the right size.

    • If your cork is too big, you'll need to cut it a little smaller.

    • If your cork is a little uneven, don't worry. Its job is to seal the water hole, which is much smaller than the cork itself.

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  • With a hot glue gun, put a drop of glue in the water key slot and place the new cork on top.

  • Press firmly on the cork for a few seconds.

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If your water key still leaks after replacing the cork, it may need to be bent back into place or may need a new spring. See an instrument repair professional or another online guide for help with this.

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