The term "fresh-air inlet" is, as its name implies, an inlet for fresh air. It is placed directly on the house side of the main trap. The connections made vary considerably. A few good connections in common use are explained below.

When the trap is in place, one of the clean-outs can be used for the fresh air. If this is done, a Y-branch should be placed in the hub of the clean-out. The Y-branch should be used for the fresh air and the run should be used for a clean-out.

A Y-fitting can be inserted directly back of the trap and the branch used for the fresh air. An inverted Y makes a good fitting to use directly back of the trap. These branches should be taken off the top of the pipe. The branch taken off for the fresh-air inlet should not have any waste discharge into it and should not be used for a drain pipe of any description.

The fresh-air inlet should run as directly as possible into the outer air, at least 15 feet from any window. The pipes terminate in a number of different ways, some with a return bend, above the ground, some with a cowl cap, some with a strainer. When necessary to run pipe through the sidewalk, a box of brick is made with a heavy brass strainer fitted level with the sidewalk into which the pipe runs. If the pipe is run into the box on the side a little up from the bottom, the possibility of becoming stopped up or filled up is not great. The fresh-air inlet sometimes terminates above the roof of the building.

Special care should be given this fresh-air inlet as it supplies fresh air to the entire system and thus keeps the pipes in a much better sanitary condition.

Sometimes when the house drain is full of sewage, air is pushed out of the fresh-air inlet and disagreeable odors are evident. This is why it should be located as far as possible from any window. Special care should be taken on the part of the plumber not to locate the fresh-air inlet nearer than 15 feet to the fresh-air intake of the heating system.

Fig. 60.  Fresh air inlet. Fig. 60. - Fresh-air inlet.

When the pipe passes through the foundation wall, the same care should be exercised as with other pipes. That is, if the pipe is 4 inches, a sleeve 6 inches should be cut in the wall for the 4-inch pipe to pass through.

Points To Remember About Fresh Air

  1. First, never should be smaller than 4 inches.
  2. Second, one size smaller than trap.
  3. Third, location, directly back of trap.
  4. Fourth, leads to outer air.
  5. Fifth, keep away from windows and intake of heating system.
  6. Sixth, always have end of pipe covered with strainer, cowl, or return bend.
  7. Seventh, make as few bends as possible.
  8. Eighth, supplies fresh air to system.