The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California

How To Design And Install Plumbing

Public authorities, as a rule, advocate elimination of the house trap, for its use decidedly lessens the discharge capacity of the sewer. Because of the rapid growth of cities, many sewers are taxed to their limit of discharge. Elimination of the trap minimizes this problem materially.

House Trap Assembly. Fig. 61 illustrates the installation of a house trap and fresh air pipe. The trap usually is referred to as a running trap, having its inlet and outlet on the same level. The trap is equipped with a cleanout extended above the finished floor, as shown in Fig. 61.

The fresh air pipe is connected within 2 feet of the trap to assure completion of a movement of air in the system, which the installation of the house trap has impaired. The fresh air pipe must be extended to the outside of the building and be provided with a cap to prevent its obstruction. Two inches is the minimum diameter of the fresh air pipe. It is recommended, however, that at least a 4-inch pipe be used. The trap must be set level and installed in a workmanlike manner to assure efficiency.

Back-Flow Valves. Back-flow valves are devices used in a drainage system to prevent the reversal of flow. They are constructed in two patterns and are classified in the plumbing industry as either balanced or unbalanced.

Back-flow valves are used commonly on house drains, or branches of the house drain, which, when subject to reversal of flow, might flood and cause damage to the building and its contents. This condition prevails in house drains subjected to capacity flow, and is especially common in house drains connected to a public sewer of the combination type.

Balanced Valve. The balanced valve is by far the most advisable installation. It is constructed in such a manner as not to interfere with the movement of air in the drainage system. Fig. 62 illustrates a valve of this type. The valve has a cast-iron body fitted with an air-tight removable cover. The body of the valve is equipped with a hub and spigot end so it can be calked into the drainage system. The interior mechanism is constructed of noncorrosive metal. It consists of a brass seat into which is fitted a gate counterbalanced with an adjustable cast-iron weight. The balanced back-flow valve offers little resistance against the flow of the sewer, which adds to its superiority.