Curved pipes are used instead of standard elbows. Their usage brings several advantages during route design and execution and mainly for their optimalization and  smaller number of connections. The curved pipes are produced from the same materials as straight ones. The required geometrical dimensions  - arch radius and arch angle are necessary to be exactly determined to the producer. The use of curved pipe is necessary to consult with the producer. It is possible to deliver other geometric dimensions as well , i.e. the length of whole pipe and the length of straight ends