USE OF FLUSH-TANKS 233 



needed in flush-tanks is not known, nor the relation between 

 amount and grade. 



With a view of obtaining more information on this appar- 

 ently unstudied subject, the author carried on some experi- 

 ments in the spring of 1897, in which he was assisted by Mr. 

 I. W. McConnell, G.E. The results of the experiments have 

 been recorded by Mr. McConnell in a thesis for the degree of 

 Civil Engineer in Cornell University. 



The sewers on which the experiments were made, chosen 

 so as to afford a variety of grade, with as long lines as possible, 

 were all 8-inch pipe, and each had at the upper end a manhole 

 about 4 feet in diameter at the bottom. Flush-tanks of the 

 usual commercial size discharge at a rate of about i cubic foot 

 per second, and, by repeated experiment, the opening from the 

 manhole into the sewer was reduced to such a size (about 5 

 inches) that the rate of discharge varied from 0.89 cubic foot 

 per second for 4 feet head in the manhole to i.i cubic feet per 

 second for 6 feet head. These conditions it was thought approx- 

 imated closely enough to the workings of a flush-tank. A 

 5 -inch opening was cut in a pine board held firmly against 

 the end of the 8-inch pipe; then a flat rubber-faced cover, 6 

 inches in diameter, was placed over the opening and held there 

 by a light stick braced against the back of the manhole, mak- 

 ing an effective plug. The manhole was filled to any desired 

 depth by means of fire-hose attached to neighboring hydrants, 

 and then, by means of a cord fastened to the stick and to the 

 cover, the contents of the manhole were discharged into the 

 sewer. The capacity of the manholes at depths varying by 

 6 inches was determined by measurement, so that by filling to 

 the proper depth any desired amount of water could be dis- 

 charged. The effect of the flush-waves was then noted at the 

 successive manholes down the line. No determinations of the 

 velocity of the wave were made, the effect being judged by the 

 depth of the wave, and by the force shown in moving gravel, 

 etc., placed in the different manholes. The wave-depths were 

 read by observers stationed in the manholes, where they re- 



