you dont say were the outside pipe is leaking from ? is it cracked? has it come  out of the elbow joint?  you can get plastic cement, it comes in a little bottel, it has a small brush made on to the lid ,  it sets hard in 5mins, becarefull  with this glue , dont inhale this stuff ,   ( hardware store for it,,,
                 mark
                
 July 2010