Back in the late '40s - early 50's my grandad hit upon building oil tanks in-place in the coal bunkers when commercial buildings were changing over from coal to fuel oil. All was going well until a city inspector got the notion that the tanks should be pressure leak tested. Grandpa attempted to discourage the notion but the inspector was adament. Knowing what would happen to the tank, Grandpa blocked the sides and top of the tank against the walls and ceiling of the coal bunker and fed the air per the inspector's instructions....
Realization finally dawned on the inspector when hairline cracks started appearing in the terrazzo floor in the lobby above the tank.
The air was quickly released and no more tests were required, and the inspector was pretty scarce.
Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
~Practitioner of the Electromechanical Arts~