MANAGEMENT OF DAIRY PLANTS 



the water seal enough to permit passage of gas. When this does 

 occur, the gas usually passes in the form of bubbles and can be 

 detected in that way. 



2. Excessive suction may draw so much water out of the trap 

 that the remainder fails to act as a seal. 



3. By evaporation, the water seal may be so lowered that 

 gas is allowed to pass. 



4. By absorption, the water may take up gas on the sewer 

 side and liberate it on the house side. 



2. Siphon Trap. This is per- 

 haps the most satisfactory of traps 

 to be ventilated. The ventilator 

 should be the same size as the pipe 

 composing the drain. It is placed 

 in the second curvature of the 

 siphon. It is most satisfactory to 

 place the ventilated trap in a local 

 sewer before that enters the main 

 sewer. Bell traps will then usually 

 suffice for the floor traps. 



3. S-Shaped Trap. This type, 

 which can be ventilated, is used frequently under sinks and to 

 some extent, also, in the main sewer system. 



Catch Basin. It is well to have the large drain that leads 

 out of a creamery connect with a catch basin a short distance 

 from the building. This basin should be round, about 3 feet 

 in diameter, and from 5 to 7 feet deep, depending on the slope . 

 of the ground. It may be built from either concrete or brick 

 as happens to be most convenient. Its use is to catch all heavy 

 materials, such as sand, nails, etc. ; for this purpose, the bottom 

 of the basin should be from 2 to 4 feet lower than the tile that 

 carries the drainage away from it. This catch basin may be 

 covered with plank and about a foot of dirt, thus preventing 

 any odors from escaping. It should be inspected once or twice 

 a year to make sure that it is in good working order. If filled 

 up to any extent, it should be cleaned the work of only a few 

 minutes. 



FIG. 7. Siphon Trap. 



