Galvanized wrought-iron pipe is generally used for this work, and all branches from this pipe should be made by means of forty-five-degree Y-branches.
Refrigerator traps do not require venting, as no conditions are present to cause siphonage of their contents.
Connections for PIate 9.
Line of Refrigerators
The waste pipe which serves a line of refrigerators should in no case be connected direct to the plumbing system, but should discharge in the same manner as the single refrigerator, as described under Plate 8. All changes in direction and all offsets on the refrigerator waste pipe should be provided with full-size cleanouts.
Refrigerator pipes should never discharge upon the cellar floor or bottom, and wherever sewage privileges exist they should not drip onto the ground. However, if necessary to discharge upon the ground, such discharge should not take place within three feet of the foundation walls, unless into a tight gutter.
Each refrigerator connecting into a line of waste pipe should be separately trapped, with its branch waste as short and direct as possible. The main line should be carried directly through the roof, and in cold climates it should be increased to 4 in. in size before passing through the roof.
The reason for this is that smaller sizes often close up at their upper ends with hoarfrost, thus stopping ventilation, which in the case of the refrigerator is a most important matter. The cellar end of the refrigerator line should be provided with a brass flap valve, in order that the upward passage of cellar air and odors may be prevented.
The use of the flap valve and the cleanout is shown in Fig. B.