I am replacing my bathroom sink faucet. The supply line is 1/2" and the instructions for the new faucet states that a 1/4" supply line is needed. The current supply line is a grey solid tube and seems to be in good condition. Can I use the same supply line for the new faucet? If so, how do I make this work?
I've used channel-locks and crescent wrenches, but a basin wrench will save you some busted knuckles. I think that your 1/2" supply is probably coming out of the wall and is grey Polybutylene pipe? If so, you need a 1/2" PB x 1/4" PB shutoff valve, or an adapter to convert to PEX and then the angle shutoff valve.
If you do indeed have a 1/2" supply to your old faucet (very odd indeed -- are you sure that it isn't just the connecting nut that is 1/2"?), then you can probably replace those with braided supplies of the proper size on each end fairly easily. If you post pics of what is going on we can give you more specific advice.