Why did my febco backflow preventer fail?
The only way that could happen is if the nut was loose and then pressurized. Those BFPs are serviceable and the nut must have been left loose. If you can find the components from under the bell you can probably reuse them. Otherwise a replacement kit can be purchased. Before reusing anything make sure the threads were not stripped, possibly from over tightening. http://www.febcoonline.ca/Repair_Kits