Is all of the piping galvanized? or just at the faucet? You might be able to remove the galvanized nipple and replace with a brass one, but if the pipes between that el and the faucet are clogged as well, you'd still have the problem. Wait for one of the pros, I wouldn't want my suggestion to be likely to break something...I'm not sure how reliably you can get the existing nipple out. Something is better than nothing.