FLUSHING 217 



increases the rarefaction, and the siphon is soon brought into 

 full play. 



" On the tank being emptied to the bottom of the intaking 

 limb the flow is checked, and the small siphon over the crest 

 of the weir draws the water from the weir-chamber, air enters 

 the discharging limb, and the siphon is vented ready for the tank 

 to again fill. 



" These siphons are largely in use and are giving excellent 

 satisfaction; made in two sizes for flushing sewers." 



A slight modification of this tank was made by Benezette 

 Williams, and the improved tank was manufactured under the 

 name of " The Rhoads-Williams Siphon." It has been much 

 used in the West and has proved very satisfactory. The cata- 

 logue gives the following description and table, which latter will 

 serve as a general index of the capacity of flush- tanks: 



" The Rhoads-Williams Siphon, as illustrated in Fig. 63, 

 consists of an annular intaking limb or bell, and a discharging 

 limb terminating in a deep trap below the level of the sewer. 

 Below the permanent water-line in the discharging limb is con- 

 nected one end of a blow-off, or relief trap, having a less depth 

 of seal than the main trap, the other end of which joins the main 

 trap on the opposite side at its entrance to the sewer and above 

 the water-line of the trap. 



" The bell has a vent-pipe terminating at a given point 

 above the bottom of the bell, and extends above the high- 

 water line. The pipe which extends above the bell has a cap 

 on it with the proper size sniff-hole for venting the siphon. 



" As the tank fills (the main trap being full) the water 

 rises in the intaking limb or bell, even with the level of the 

 water in the tank, until, reaching the end of the vent-pipe, a 

 volume of air is confined in the two limbs of the siphon between 

 the water in the intaking limb and the water in the main trap. 

 As the water rises higher in the tank the confined volume of 

 air is compressed, and the water is depressed in the main trap 

 and in the blow-off trap. This process goes on until the water 

 in the tank reaches its highest level above the top of the intaking 



