There is a thing called Induced Syphonage when you have a pipe with liquid in it coming from a tank with liquid in it if the liquid escapes from the loose pipe by natural drainage, it can suck up the contents of the tank and empty it even if its inverted . Much the same as when you nick/syphon petrol out of a car but with this you dont need to suck. All so if there was a temprature increase it may of increased the pressure in the tank to increase to forces of Induction to cause the leak. What do I no im only a simple Plumber

4D