68 VETERINARY HYGIENE 



up the open ends of the drains and ventilating pipes and pumping 

 in air under pressure sufficient to indicate on the gauge used. If 

 the gauge does not show that this pressure is being maintained, it 

 indicates a leak or leakages. These can generally be located by 

 filling the pipes with dense white smoke, afterwards plugging the 

 pipes and applying the same pressure as before. This will force 

 the smoke out at the defective parts and enable them to be located 

 and made good. This test should be continued until the gauge 

 remains steady and proves that the drains are sound and can be 

 passed as satisfactory. Any desired pressure can be applied and 

 the air or pneumatic test can be made very severe, in fact a greater 

 pressure can be exerted inside the pipes than could ever occur under 

 ordinary circumstances. Under normal conditions, however, there 

 is little or no pressure inside the drain pipes, so that an apparatus 

 that will give about oz. pressure per square inch will apply a 

 sufficient test both to the drains and to the trap seals. One inch 

 head of water represents 577 oz. per square inch, and as the seal 

 for small traps is usually 1| to If inches they should be able to 

 stand a test of -| oz. pressure. 



The best apparatus for applying the air and smoke tests (either 

 for high or low pressure) is the Burn and Baillie Patent Drain 

 Testing Machine, which is a combined air and smoke testing 

 apparatus and can be used for either or both tests as above described. 

 It consists of a copper cylinder in which is burned specially pre- 

 pared smoke paper, or cotton waste soaked in whale oil (paraffin 

 should not be used as it is liable to flare in the box). The cylinder 

 is surrounded by a copper tank which is filled with water to keep 

 the fire box as cool as possible. A copper cover or float is placed 

 over the cylinder which, dipping into the water in the tank, forms 

 an air-tight joint. A strong double action bellows is connected 

 with the fire box. When using the apparatus for the air test the 

 tank is filled with water and the float put in position. Rubber or 

 flexible metallic tubing connects the outlet of the machine and the 

 drain to be tested. Fresh air inlets and all air outlets are closed 

 with rubber stoppers and air is then forced into the drain with 

 the bellows, a few strokes of which causes the float to rise. If the 

 float remains stationary, after the stop-cock on the apparatus is 

 closed, the drain is tight, but if it falls a leak is indicated. In order 

 to detect the position of the leak or leaks the smoke test may then 

 be applied. The smoke paper or cotton waste is placed in the 

 cylinder and lit, the bellows are worked, and when dense smoke is 

 formed the cover is put on and the smoke blown into the drain. 

 The plugs at the air inlets and outlets are removed until smoke issues 



