Ever since we had some (unrelated) plumbing work done in another part of the house, which required turning off the mains water supply, one of our faucets has been making a loud “machine-gun” noise whenever it is turned on. Do I just have a bad washer in the faucet (coincidence), or could this be related to the other work (maybe an airlock)? If so, how do I clear it?
Forget about an “airlock”. Air is removed from pipes the first time a faucet is used. It is either a worn stem, or a bad washer. It is also most likely a coincidence or something that was going to happen and turning the water off just speeded up the process.