May be in the silly question category: In draining my home's water lines, after shutting off the supply, when I start opening the faucets do I open both cold and hot or only cold?
Depends on the purpose. Do you want to drain all lines? Let's say you are working on a 2nd floor cold faucet...I'd just open a cold line on the 1st floor + the upstairs cold faucets. No need to open & drain the hot in that case.