THE FLOW OF WATER IN CONCRETE PIPE. 81 



average, because observations were not of a character permittting reduction for indi- 

 vidual pipes. These pipe measurements included the chamber and transition- 

 section losses, of all kinds, at both ends of each pipe because it was not considered 

 advisable at that time to provide piezometers, or other devices, necessary to the 

 direct measurement of the pipe losses separately. These observations were reduced 

 by taking advantage fo the fact that the pipes were of various lengths and the same 

 type of construction, including the chambers, so that the assumption could be reason- 

 ably made that the wetted surfaces are practically identical in character: hydraulically , 

 and that chamber losses are the same in all chambers for any given flow conditions. 

 Losses in the pipes were computed, using assumed pipe friction-loss coefficients, 

 Which computed pipe losses were subtracted from the measured losses. These com- 

 puted residual losses were than compared and the set most nearly consistent selected. 

 The coefficient used in obtaining the selected set was assumed to be an average for 

 the several pipes and an approximately correct average because of the method used 

 and the probability that not all pipes were in the same condition as to foulness, 

 hydraulically considered. The value selected is believed to quite closely approxi- 

 mate the truth, because some of the siphon pipes are so short that the total friction 

 loss in them is very small as compared to the chamber losses. 



While the observations are not such that definite conclusions there- 

 from would be warranted, still the indications are that a steel pipe, 

 built up of relatively long sections, well jointed and lined with a 

 smooth cement coating, gives a very efficient surface. Of course the 

 primary object of this coat is to prevent the corrosion of the metal 

 interior but is gives an added satisfaction to know that this prevention 

 has been attained without sacrifice of capacity, for a given sectional 

 area. If anything, the fractional loss is less than it would have been 

 in a new metal pipe and the latter material would have continually 

 lessened in capacity while the lining will probably remain about the 

 same, after the first slime coat is acquired. 



No. 39, Experiment M-2. — Kondout pressure tunnel, 1 Catskill 

 Aqueduct, N. Y. — At the Rondout River crossing the Catskill 

 Aqueduct takes the form -of a circular pressure tunnel, excavated 

 in solid rock and lined with concrete. From the standpoint of 

 capacity the tunnel is, in essentials, a circular pipe, constructed in 

 place. (See PI. IX, fig. 1.) 



The tunnel consists of vertical downtake and uptake shafts joined 

 by an approximately horizontal tunnel. The developed length of 

 the tunnel is 24,880 feet. About 16, 000 feet from the intake a vertical 

 drainage shafts extends from the ground line down to the tunnel. 

 As the ground line at Rondout River is 300 feet below the hydraulic 

 gradient, this shaft is, of course, sealed. 



In August, 1915, F. F. Moore, designing engineer of the board of 

 water supply, conducted a series of experiments to determine the 

 friction losses in this tunnel, from the drainage shaft to the outlet, a 

 distance of 9,102 feet. The pressure head at the drainage shaft was 

 measured with a mercury manometer of the pot-and-column type. 

 Mercury readings were corrected for temperature of air and of water 

 in the tunnel. The temperature of the water in the pipes to which 

 the manometers were attached was assumed to be controlled by the 

 ground and therefore unchanging. The mercury column was also 

 read with no flow in the tunnel, thus establishing the levels between 

 gauges. 



The elevation of the water surface at the outlet was determined 

 by steel-tape measurements from a bench on the floor over the 



1 Eng. Rec, Mar. 11, vol. 63, 1911, p. 279; Eng. News, June 1, vol. 65, 1911, p. 654; Water Works Hand- 

 book, by Flynn, Weston, and Bogert, New York, 1916, p. 284. 



164725°— 20— Bull. 852 6 



