When i flush the loo,i have a leak coming from the underneath of the cystern where the pipe to the pan starts off.I'm guessing that maybe a washer has broken or something like that as no matter how tight i screw the fitting nothing stops it from pouring out.I now have a bucket behind my toilet just to catch the water.The leak is coming from underneath the cystern and not at the joint where the pan is.Can i do the job myself by tying up the ball cock and taking out the pipe and getting a new liquid tight fitting from say B+Q?Is this a simple job for a novice like myself?