To install a filtered water faucet, choose whether you'd like to drill the hole. You might want the hole close to your current faucet, or you might want it at the side of your sink, rather than the center. Some under-sink systems have relatively short pipes to connect the filters to the faucet, so this might affect where you drill the hole, too. In short, there's no right or wrong location to drill the hole, as long as it allows you to send filtered water directly into the sink from the faucet.