If you lack air power get a longer piece of pipe. Leverage is your friend. Don't let the socket twist sideways on the nut or you'll take the flats off - not a good thing. Sometimes I need to block the socket/extension/whatever so that I can shove w/o having the socket twist sideways.

Is it an Allen (socket) head? If so be doubly careful not to twist it. The socket heads hold the wrench really well but if they round out they're a double PITA.

Dan