WATER SUPPLY, PLUMBING, ETC., FOE COUNTRY HOMES. 39 



Avith a valve may be installed below the tank, as shown respectively 

 in figures 29 and 28. The discharge chamber should be fitted with 

 an outlet set above the siphon which will allow the sewage to escape 

 in case the siphon becomes clogged. 



A concrete mixture of 1 part cement to 2 or 2^ parts sand to 4 or 5 

 parts of broken stone or gravel should be used in the construction 

 of the tank, and it is a good idea to use the oil-mixed method pre- 

 viously noted (p. 4) to help to waterproof the concrete. 



THE AUTOMATIC SIPHON. 



The automatic si- 

 phon may be installed 

 to operate as fre-- 

 quently as may seem 

 desirable. Figure 31 

 shows a 3 or 4 inch 

 automatic siphon in- 

 stalled. The siphon 

 operates as follows: 

 As the liquid enters 

 the discharge cham- 

 ber its weight in- 

 creases with increas- 

 ing depth, and the air 

 between the water 

 surface in the bell and 

 the water inside the 

 "siphon leg" is com- 

 pressed. As the water 

 outside increases in 

 depth the compression inside becomes greater until the water outside 

 reaches the drawing or discharge depth for the siphon. Then the 

 inside pressure is sufficient to force the water in the siphon leg around 

 the bend, instantly relieving the compression. The water from the 

 tank then rushes in to fill up the space which was occupied by the air 

 and starts the siphon, which continues until "the outside and inside 

 pressures are again equalized. 



The following table gives working data and dimensions, as shown 

 in figure 31, to be used in installing 3, 4, and 5 inch siphons. Sizes 

 of 5 inches and over are constructed a little differently from the 3 

 and 4 inch sizes, although the working principles are the same. 



Fig. 31. — Three-inch or four-inch automatic siphon installed. 



