150 SEWER DESIGN 



gasket, by taking up in the joint space that should be filled 

 with cement, was a detriment rather than a benefit. Mr. 

 Senior 's experiments were all made on six 2 -foot lengths of 

 6-inch pipe, and the mortar all mixed i : i. His results in 

 detail were as follows: 



When the water was turned onto the joints within 3 or 4 

 minutes after the cement had begun to set (15 minutes after 

 the first joint was made), the leakage through Rosendale 

 cement was at the rate of 150,000 gallons per mile per day, 

 decreasing to 30,000 after 72 hours. The Portland cement, 

 under the same conditions, showed a first leakage of 120,000 

 gallons, decreasing to 4500 after 72 hours. 



When, however, the cement was allowed to stand 30 minutes 

 before water was admitted, the leakage through Rosendale 

 joints was at first 70,000, reduced to 25,000 after 72 hours, 

 and for Portland the leakage was 60,000, which became 4,000 

 after the same time. 



In using gaskets, water was turned on in 10 minutes, or 

 before the cement was set, so that the full benefit of the gaskets 

 was brought out. With Rosendale the first leakage was only 

 26,000 gallons, and after 72 hours it had decreased to 8000 

 gallons per mile per day. With Portland, while the first leak- 

 age was 11,000 gallons, after 72 hours it was but 5500 gallons, 

 or a small and insignificant amount. The results of this last 

 work as well as that of Mr. Coffin show that even under the 

 best conditions there is some leakage; but that if the joints 

 are well made this amount can be reduced to about 4000 gallons 

 of water per mile per day for a 6-inch pipe. (Compare with 

 p. 144.) For larger pipe the increase would probably be pro- 

 portional to the area of the joint. 



If the joint space increased regularly both in width and 

 length, this area would be approximately proportional to the 

 square of the diameter. But the widths are uniform at f inch 

 up to and including lo-inch pipe and all other sizes have a 

 ^-inch space for standard pipe. For deep and wide socket 

 pipe, the space is always | inch. The area then depends on the 



