Documents of pressure equipment issued by its manufacturer on the basis of design and calculation documentation – confirmed by the CE declaration of conformity and by the Office of Technical Inspection. When purchasing a tank, it is worth making sure that it is also equipped with a condensate drain connector, pressure measurement connectors, and a manometer with a manometric tap. It is also worth asking the tank manufacturer to ensure that the safety valve supplied by him also has a certificate of its operation checked in the tank manufacturer’s laboratory, confirmed by the local Office of Technical Inspection.