The toilet (picture below) when flushed only uses about half of the water in the cistern and also the `flush` handle only comes returns halfway when flushed, the cistern is around 16 years old so I suspect it probably needs a new flushing unit, if so, is this easy enough to do ? Can anyone give me some instruction? I have another toilet in the house so not bothered if this one out of action for a few days while the job gets done.