The plumbing for office buildings is naturally varied, but consists largely of lines of lavatories and toilet rooms, both public and private, successive floors often being duplicates. The continuous vent principle may often be applied to lines of fixtures in office buildings to the benefit of the plumbing system and with a saving over common methods in both material and labor. In office buildings and other buildings containing many stories, the following limitations in the size of soil-pipe stacks should be observed.
Regardless of the small number of fixtures that may enter it, a soil-pipe stack in any building between five and twelve stories in height should not be less than 5 in. in diameter, and in buildings of more than twelve stories, this size should never be less than 6 in.
Plate XXXVI. Plumbing For Office Buildings
For sizes of main vent lines, the following regulations should be adhered to:
Main vent lines for water closets on three or more floors should not be less than 3 in. in diameter; a main vent line for fixtures other than water closets on less than seven floors should be not less than 2 in.; for less than nine stories 3-in. main vent; for nine to sixteen stories, 4-in. main vent; for sixteen to twenty-two stories, 5-in. main vent; for twenty-two stories and up, 6-in. main vent should be used. These requirements result in centralizing the plumbing, as it would become an expensive matter to run large stacks through many stories simply to provide for a few fixtures.
Whenever water closets are located on different floors, as in
Plate 36, they should each be vented, with the exception of the top water closet. When two water closets, however, are located close together on the same floor, it is not essential to vent both fixtures if they waste into the same Y branch. It is sufficient to prevent siphonage, to vent only the water closet that is the farther from the stack. When two water closets discharge into a double fitting, a mutual vent may be taken from a hub near the junction of the two branches. Fittings of this kind are easily obtained, and it will be seen that the one vent taken from this point vents both the fixtures.
Many plumbing ordinances call for the venting of all water closets except a water closet above which no other fixtures enter. As a matter of fact, it is very difficult to siphon a water-closet trap even partially, by the discharge of other fixtures than water closets. Therefore, it does not seem necessary to vent any water closet which is the only fixture of its kind on the stack, provided the water closet is within 3 ft. of the stack. For the same reason it does not seem necessary to vent either of two water closets discharging into a double fitting, and located on the same floor close to the stack, if other water closets do not discharge into the same stack. Judgment must be used in these instances, however, for batteries of fixtures such as lavatories might be located on the same stack as a single water closet, and be able to throw enough waste into the stack to endanger the water closet.
If it could be depended upon that people of high intelligence were always to install the plumbing system, and also that in every case they could be depended upon to install the work honestly, there are many conditions constantly arising under which a safe piece of work could be constructed without the necessity of venting, whereas venting under the circumstances is required by ordinance. Because dependence of this nature cannot be made, iron-clad rules must be adopted to make the attainment of perfect work a surety.