We had a leak in our back room. The landlord fixed the roof and solved the problem. Sounds like you might need a new unit. We have the same thing in our place. They're fairly new so leaks aren't an issue. The water tank may have corroded through. They do that after a while. Good luck with it.
when we went back to the states to find new people to rent our house while we stayed there for the month the pipes in our shower leaked... it warped the floor boards and we had to rip up half the floor to get it fixed... not counting the $270 for the plumber to come out and tell us it was just a loose screw thing... 5 minutes and he was gone...
We have a leak as we speak and the council are coming to fix it tomorrow! At last! Our house isn't council because we own our home, but the lady in the flat above us is council and the leak is to do with her, so luckily we don't have to pay for this one!
One of my windows leaked at the bottom of the frame because some sealant hadn't completely covered the gap. About 2 years ago, there was a very wet and windy winter (even more than usual) and I couldn't get to sleep because I kept hearing a high pitched pinging noise. One night I happened to get up and check the windows (the thought hadn't occurred to me before that for some reason), and I noticed a little river running down off my windowsill, onto my radiator and down onto a large wet patch on the floor. This wasn't noticeable because it was to the side of my TV, where all the cables and plug sockets were... needless to say, we got it fixed quickly and I put a bucket down for fear of electrocution when I switched the TV on.
Not the most dramatic thing, but hey, I managed to spin a whole story out of it