DISCUSSION OF " FLOW OF WATER IN CONCRETE PIPE." 1 



By Kenneth Allen, Sanitary Engineer, Board of Estimate and Apportionment, New 

 York City; Arthur S. Bent, Engineering Contractor, Los Angeles, Calif.; F. C. 

 Finkle, Consulting Engineer, Los Angeles, Calif.; Allen Hazen, Consulting 

 Engineer, New York City; J. B. Lippincott, Consulting Engineer, Los Angeles, 

 Calif; H. D. Newell, Project Manager, Umatilla Project, United States Recla- 

 mation Service, Hermiston, Oreg. 



DISCUSSION BY MR. ALLEN. 



It is fortunate that in these times of soaring prices for cast-iron 

 pipe a competing material for many purposes is found in reinforced 

 concrete, for a careful perusal of the author's important and exhaus- 

 tive investigation demonstrates that if we can be sure of the best 

 material and fabrication, this material can be safely used — at least 

 under reasonable head — and with economy. 



In estimates for a 48-inch force main 12,350 feet long, based upon 

 prices ruling in the summer of 1916, there was found a saving of 

 $84,000 by the adoption of precast concrete pipe instead of cast iron, 

 or 44 per cent of the cost for the latter. The difference to-day 

 (Feb. 16, 1918) would be still greater. 



Precast concrete pipe appears to be particularly well adapted to 

 sewer construction for several reasons: Joints are infrequent and 

 consequently infiltration should be small; the width of trench is a 

 minimum, causing less inconvenience to traffic and reducing the 

 excavation; there will be little danger from corrosion due to acids 

 sometimes observed with cast iron when used for sewers ; and, finally, 

 instead of a marked decrease in carrying capacity, due to tubercles, it 

 would appear that the excellent surface obtained when first laid is 

 subject to little deterioration from time. This means that for the 

 same ultimate capacity we may assume no larger diameters and 

 gradients, and possibly less, than for cast iron — certainly less than 

 would be justified with ordinary brickwork or mass concrete. There- 

 fore the best precast pipe would seem particularly adapted to the 

 construction of those sewers where, on account of the flat topography 

 or in order to reach the outlet at the desired elevation without 

 pumping, minimum gradients must be employed. 



With a sewer 4 feet in diameter, for instance, and with a minimum 

 velocity when flowing full of 2\ feet per second, the frictional loss 

 per mile will be with — 



New cast-iron pipe=2.11 feet (Williams and Hazen formula C w -~ 130). 

 Old cast-iron pipe =5.17 feet (Williams and Hazen formula C w =80). 

 Ordinary mass concrete =2.72 feet (author's formula C s =0.31). 

 Best precast concrete =1.91 feet (author's formula C s =0.37). 



In other words, under the conditions assumed, the friction loss 

 with cast-iron pipe will vary from 1.1 to 2.7 and with ordinary con- 

 crete work will amount to 1.4 times that to be had with the best 

 precast concrete pipe. 



With any concrete pipe subjected to pressure, as in the case of 

 slabs, bins, or concrete ships, reliance must be placed on the excellence 



i The original manuscript of the preceding paper was submitted to the men named, who in their varied 

 experiencesapr:unili:ir\viihcoii(;n'l(|ii|irsrortlieeonveyanceofwaUTforirrigation,powcr,andmiini(:ii)al 

 use, and also for the conveyance of sewage. Criticism and discussion of the manuscript were asked for. 

 Acknowledgment is now made of the time and labor expended gratuitously in preparing the discussion 

 and comments given here. Throughout the discussion ,! the writer" will refer to the name heading that 

 particular part of tho discussion and " the author " will refer to the author of tho paper. 



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