I have done it a few times... cup of vinegar and a scoop of bicarb

I was actually really surprised when I heard that people clean their washing lines, (as in WTF?? LOL) but I figured I'd give it a go, turns out my clothes line gets extremely dirty!
Wow! I've never thought of that either!

Thanks for the info everyone. At the moment the hot tap isn't even connected to our washing machine. I'll need to get it connected and give it a clean.