We're finishing our basement and I want to re-run the kitchen supply line because the 1/2'' copper runs underneath (perpendicular) to the 16'' on center joists and thus lowers the ceiling by a full inch (it will need to be shimmed). I want to install PEX that runs through the center of the joists thus saving the 1'' loss the copper entails.

The copper pipe is a regular 1/2'' branch line. What size PEX would I need to replace that with? Thanks for all your help!

Hi Snucky:

1/2" copper to 1/2" PEX should be fine for a kitchen sink and dishwasher.

If you were feeding a shower or more than the two fixtures above I would recommend 3/4" PEX, but this case only warrants 1/2" PEX.

Mark