The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
How To Design And Install Plumbing
Anti-Siphon Traps. Fig. 140 illustrates anti-siphon P-traps which may be used on the plumbing installation. These traps are to be dealt with in the same manner as are ordinary P-traps as far as ventilation needs are concerned.
Internal Partitioned Traps. The trap illustrated in Fig. 141 forms its seal by means of an internal partition. If the partition is made of indestructible metal, not subject to the corrosive tendencies of the waste, this type of trap may be used. Their use is not recommended, however, unless positive proof can be shown that this caution has been observed. State and local health authorities generally require rigid tests before this form of trap is permissible.
Bell Traps. Bell traps, Fig. 142, are intended only for certain kinds of fixture use. Their installation is common on indirect or local wastes, such as refrigerators and similar fixtures. The purpose of a bell trap is to prevent the passage of odorous gases. They are not intended to withstand the rigorous conditions which prevail in plumbing systems. The seal in a bell trap is formed by a raised metal rim that is cast into a depressed bowl. A furrowed bell or cap, placed over the rim, forms a small water seal.
Prohibited Traps. The S and 3/4 S-traps, Figs. 143 and 144, are forms of traps which should not be used on plumbing installations, because it is entirely impractical to ventilate them properly.
These types of traps were popular when the crown method of ventilation was considered good practice. Crown ventilation, however, has been obsolete for many years because of its ineffectiveness. One of the difficulties with this method was complete stoppage of the vent in a short time. The S and 3/4 S-traps constitute perfect siphons and without ventilation should never be installed.
The bag trap, shown in Fig. 145, is an extreme form of S-trap and one that is objectionable. It is no longer used and makes its appearance only in the older types of plumbing installations. It is seldom encountered except in repair work, and then should be replaced.
