What is a local vent?

A local vent is a line of pipe connected at the rear of the water closet and under the seat, for the purpose of carrying off the noxious odors incident to the use of the fixture.

Is the local vent strictly a sanitary measure?

It is not. No ill effects result if it is not used, and it is put in simply for the sake of comfort.

What material should be used for local vents?

Copper or galvanized sheet iron is usually used.

Where should the local vent be carried?

Into a heated flue if possible, above all openings. If there is no heated flue at hand, then through the roof.

Why is it better to enter the local vent into a heated flue than to carry it through the roof?

The heat of the flue creates a circulation by aid of which the odors are carried at once into the open air through the chimney. If carried through the roof the upward tendency is small, and often the tendency will be downward.

Why should the local vent enter the flue above the highest opening?

Otherwise the foul air might be driven through some chimney hole into other rooms of the house.

What are the two principal methods of running local vents where there are a number of closets in the house?

One method is to carry each vent separately from the water closets to the flue. Another method is to run the several vents into one main local vent, which is carried into the flue.

What advantages are claimed for the method of separate vents?

Where each vent branches into one main vent it is very often the case that noises, conversation, etc., can be overheard in different parts of the house. When this method is followed, especially in double tenement houses where closets back up to each other on opposite sides of the partition, the germs of contagious diseases may be carried through this vent from one tenement to another.

In what way is a draught sometimes created for the local vent?

If there is no heated flue at hand, or if the vent has to be carried through the roof, a gas jet can be kept lighted at the bottom of the vertical pipe. This warms the air and creates an upward draught.

What sizes of pipe are permissable for local vents?

Not less than two-inch pipe should be used for a single water closet. Where two, three, or four vents enter a main vent, the latter should be increased to at least three-inch.

Name some general requirements of local venting.

Pitch all vents toward the fixtures they serve in order to take care of any condensation, and to assist the draught; use as few turns as possible.

How should chimney connections of local vents be made?

The local vent pipes should run either into a piece of cast iron pipe, or a copper pipe, as they will not rust out. This piece of pipe should be cemented into the chimney. Care should be taken that the pipe does not project beyond the inner face of the chimney, as soot might eventually partially or entirely close the end.