On June 11th we had our well pump replaced. On June 14th one of our water softener tanks burst. Recently we have begun to piece some information together. 1. Our well pump is about 500 ft away from the entrance into our home. 2. The well is about 100 ft below the entrance to our home. 3. The water comes into our home and then ts one pipe goes to the pressure tank and the other to the water softener. The installer closed off the valve to the pressure tank but not to the house/water softener. During the pump installation my son noticed a dent in the tank sort of a football shape. We believe that the water leaving the pipes at the the well created a vacuum in the tank which caused it to collapse and create stress fracutres. Subsequently it burst three days later. (The engineer believes this also, but we had to point it out) Has anyone every herd of this before? and How common is it that tanks break? Any help would be appreciated.