I have a hot water tap in my downstairs loo that will not turn on and seems like it's seized. Is it a case of replacing the tap head gear ? If so, I know I need to turn off the gate valve in my airing cupboard and drain the hot water but because I can't turn this tap on will I have a problem when I come to take it apart if I haven't drained the hot water from this section of pipe ? Sorry for being a bit thick on this. I'm a bit of a plumbing novice to say the least !!