A plumber is a person who performs installation, repair or maintenance services on hydraulic systems and equipment that are powered or controlled by hydraulic media or fluids. Plumbers are responsible for performing diagnostic work, installation, maintenance and repair of various equipment using various hydraulic tools and technologies. The work of a plumber requires knowledge of the principles of physics and chemistry, as well as knowledge of mechanical and electrical engineering. Those employed as plumbers must also have good technological taste and be able to solve problems in creative and innovative ways.