Ключевые слова: abstract, background, black, canal, construction, contractor, detail, drain, drainage, drainpipe, drinking, ducts, engineering, grisslehamn, improve, industrial, industy, infrastructure, investment, laying, maintenance, material, new, pile, piled, pipe, pipeline, pipes, piping, plastic, plumber, plumbing, polymer, polyvinyl, public, pvc, residential, round, sewage, sewer, size, stack, striped, supply, sweden, tube, tubing, water, wideangle,