There should be a Pressure Release Valve on your system that should have discharged the water through a safety pipe outside. This should have happened at 3 bar. If the PRV is faulty or missing you will need to either change it or add one. This is very important. If you want to know what happens if you dont go onto UTUBE and type is mythbusters exploding water heaters
tyemanone, December 2009
Bleed the radiators of water to reduce the pressure
