File:San Francisco water (1925) (14783840555).jpg

Identifier: sanfrancwat4192581930spri (find matches)
Title: San Francisco water
Year: 1922 (1920s)
Authors: Spring Valley Water Company (San Francisco, Calif.)
Subjects: Water-supply
Publisher: San Francisco, Calif. : Spring Valley Water Co.
Contributing Library: San Francisco Public Library
Digitizing Sponsor: California State Library Califa/LSTA Grant

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Text Appearing Before Image:
ing placed be-tween the upset edges of each part. They arethen strapped together. This holds them inplace while the pipe is run through a hugehydraulic press that exerts a tremendouspressure on the bar, squeezing it down ontothe plates with such force that the plateswould tear before they could be pulled loosefrom the bar. This gives the pipe a smoothinterior, offering the least resistance to theflow of water. The pipe is heated and thendouble-dipped—that is, it is lowered into avat of hot asphalt, then withdrawn until theasphalt cools to the sticky stage, then re-dipped. This second dipping is a quick one,the pipe being lowered into the dip and with-drawn as rapidly as possible. The seconddip makes a thick coating. To further pro-tect the metal the pipe is then put into aspiral wrapping machine and wrapped witha felt similar to roofing felt, while a streamof hot asphalt is sprayed on the pipe andpaper. By this method the steel is protectedfrom corrosive action of moisture and soil.
Text Appearing After Image:
Large screens protect the lakeside tunnels against intrusion of foreign substances SAN FRANCISCO WATER April, 192S Pipe-laying, like pipe-making, is a ma-chine-job nowadays. Very little of the laboris done by human hands. A big drag-linescraper, moving along on its own power,scoops out the dirt to form the ditch. Thepipe is put on trucks by a crane and hauledto the job, where another powerful crane,built with caterpillar feet and able to moveover the roughest ground, takes the pipe andplaces it in its proper position in the ditch.The usual riveted joint is made in connect-ing the lengths into one long continuouspipe. Riveting is done by air, and the fa-miliar sound of the riveting hammer canalways be heard. Large gates will be placed in the line andconnection made to the present lines, so thatthe whole system of supply pipes may beoperated to the best advantage, thus insur-ing as constant a supply of water to SanFrancisco as is humanly possible. Beginning at San Andres, for the firsts

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