There is nothing very complicated in the plumbing system of the small house. Certain sanitary precautions should be observed in arranging lines, however. For example, the termination of the main soil-line should not occur near a dormer or other window, nor should the termination of the fresh-air inlet be located in the cellar wall under a door or window. The system when completed in the roughed-in form should be tested for leakage by filling it with water, and when all the fixtures are connected and every part of the system is supposed to be in working order, either the peppermint or the smoke test should be used to detect any further possible leakage. The peppermint test consists in pouring hot water and 2 ounces of oil of peppermint into the top of the system from the roof, after all the fixture traps have been filled with water, and then detecting with the nose where the leaks are. If the smoke test is employed, a smoke machine is best. Old oily rags and tar paper are burned in the machine, which has its flue connected with the fresh-air inlet, and the smoke is pumped through the system until it appears escaping from the soil-line extension on the roof. If there are any leaks, the odor and the smoke stain will attract attention to them, and if the water-closet traps in the bowls are defective, the yellow stain of the smoke will make it very evident. _Refrigerator Connections_ The drainage from the refrigerator should never be directly connected with the drainage system of the house. If the plumbing code requires any connection at all, the usual arrangement is to drip the ice-box water into a lead-lined tray which has a pipe at least 1¼ inches in diameter that carries the water down to the laundry-tubs in the cellar and spills it into them. On the other hand, if there are no plumbing regulations, it is best to drain this water off into a small hole in the ground into which has been thrown gravel, and this will permit the water to soak into the surrounding soil. _Water-Supply Pipes_ If there is a city supply of water, the small house should have a main supply-line from the water-main in the street of at least ¾-inch diameter, but this does not give the service that a larger pipe, say a 1¼-inch pipe, does, for often with the smaller pipe, if the water is being drawn in the kitchen, none will be secured from the faucets in the second-floor bathroom. The kitchen-sink should have a service pipe of at least ¾ inch, the tubs the same, and the lavatory ½ inch.