Have dryer in basement but want to move it upstairs... another 25 feet or so. Can I splice additional cable to the existing by splicing at the existing box location ?

Considering moving my dryer to new location about 20 feet further from present location. Is it within code regulations to splice the 10-3 cable ?

Sure, as long as you splice the cables in a junction box with a cover.

Two #10-3 with ground would need a box with a minimum of 17.5 cubic inch of volume space.

A 4" x 4" x 2" deep box has 32 CI of space, and should be sufficient.

The conductors need to be at least 6 inches long in the box.

Of course, you need wirenuts that can handle two #10 wires.

If you use a metal box, be sure to have a grounding jumper connect to the box.

3M red Scotckloks or equal will work.

Be sure the box is accessible, does not get hidden behind drywall, or any other finish.

Be sure to use the proper cable connectors as the cables enter the junction box.

If the box is metal, be sure to use a grounding jumper to connect to the box.

Please make sure that you shut the breaker off prior tocutting and splicing the wires.