Tests 



135 



In November, 1916, some McCracken sewer pipe made of one 

 part cement to two and a half parts of sand, and some vitrified clay 

 sewer pipe were tested for absorption. The clay pipe was being 

 used for street sewers in Tucson. The McCracken cement pipe had 

 been offered in the bidding:, but was not accepted on account of 

 undue prejudice against the use of cement pipe for sewers. The 

 results of the tests are given in Table XVII. They show that clay 

 pipe mav have a very low ])crcentage of absorption and yet be very 

 pervious to water. 



TABLK XVII. .\r.SORPTlOX TESTS OX SEWER PIPK, TUCSON, 1916 



Sample 



Absorption 



Perviousness 



1 Clay tile, nearlj" vitrified 



" " thornughly vitrified 

 " " nearly vitrified 

 " " semi-vitrified 

 Cement pipe, hodv 

 " bell 



3.07 



2.43 

 2.98 

 5.59 

 4.61 

 2.89 



No seepage 15 pounds 5 

 minutes 



Sweat uniformly all over. 

 " on Yz of surface 

 " all over in ^ min. 



Not tested for seepage 



INTERNAL FRICTION TESTS 



Tests to determine the friction loss in hand-made cement pipe 

 were made at the University Farm in 1916. The object was to 

 furnish a basis for the design of two additions to the distributing 

 system. 



All of the old line Avas 12 inches in diameter and all except the 

 first 360 feet was built with rectangular outlet boxes spaced every 

 36 feet. These boxes are 22 inches long by 30 inches wide, and have 

 two discharge notches at the top, one toward the right of the pipe 

 line, one toward the left. The flow of water expands on entering 

 a box and contracts on leaving, so that there is a considerable loss 

 of head in each box. These boxes were designed by a former super- 

 intendent of the farm. The design is not to be recommended. 



In making the tests, the discharge of water was measured over a 

 weir just before entering the pipe line, and the water levels were 

 noted in each box by measuring down from a point on the top. A 

 line of levels had been run to determine the elevations of the points 

 on the tops of the boxes. The cement pipe when new had received 

 a coat of neat cement wash on the inside surface. 



After the additional pipe line had been laid in the summer of 

 1916, pipe friction tests were made in that portion which had 12- 

 inch outlet risers and valves of the California pattern ; that is, the 

 riser is a joint of pipe cemented into an opening in the top of the 



