108 BuLivETiN 86 



RISERS 



The risers are made by cutting a hole in the side of a joint of 

 pipe, and inserting another joint, the end of which is cut in the shape 

 of a saddle. The two pieces are then cemented together. For ma- 

 chine-made pipe the cutting and shaping are done a few hours after 

 the pipe is made, but hand-made pipe, being much less hard, can be 

 cut in the field. Often the holes are cut after the pipe line is laid. 



The making of Y's and T's and other fittings such as bends is 

 an undeveloped business. The present method of making the pieces 

 and cementing them together is unsatisfactory. It is slow and ex- 

 pensive and the joints when made look patchy. These specials 

 should be cast in one piece in special molds, using rich mortar or 

 thicker walls. The molds, especially in the large sizes, would be 

 expensive, but contractors whose business is pipe making or laying 

 can afford to have them. 



The riser valves are usually cemented onto the risers in the field, 

 though it is preferable to do this work in the pipe yard, if the lengths 

 of the risers can be known in advance. Cement work of this nature 

 can be cured more easily and better in the yard than in the field. 

 Risers should be of smaller diameter than the pipe line. If they are 

 of the same diameter, the line is unduly weakened at the point where 

 the hole is cut for the connection. 



EFFECT OF HIGH TEMPERATURES 



On account of the high temperatures in midsummer in southern 

 Arizona, pipe laying at that time is attended by some danger. The 

 expansion and contraction of mortar and concrete with changes in 

 temperature are high, and a freshly-laid pipe line has little resist- 

 ance to breaking if contraction occurs at once, usually the first night. 

 This was illustrated at the University Farm in June, 1916, when a 

 new pipe line a quarter mile long broke at almost every joint. It 

 became necessary to uncover the line and make the joints over 

 again, and in some cases a third time. The work had been guaran- 

 teed and the loss fell on the pipe contractor. Another instance oc- 

 curred the previous summer in the Antelope Valley, at the head of 

 the hot Mojave desert, where every joint for two miles had to be 

 made over. In case the pipe laying cannot be put off until fall, then 

 the only precautions possible are to have the pipe well wetted before 

 laying, to backfill the trench promptly and deeply, to run water 

 through the pipe at once, and possibly to lay pipe only from daylight 



