Sewer and Connections

Also, by giving the sewer too much pitch, the water travel may be so rapid that the water will run ahead of the solid matter, allowing the same to be deposited in the pipe to present an obstruction to the next discharge of matter through the pipe. The average fall which is given sewer- and soil-pipes, of inch per foot, is more than ample. Table II shows the fall required in different-sized sewers to give an average velocity of 276 feet per minute in the flow of sewage—which velocity of flow will carry all matter from the sewer.

It must be borne in mind that the only way that sewage is carried along in the pipes is by flotation; and there is no other manner of doing this. There is no hidden force in the sewer to carry away the sewage, and solid matter re quires water to dispose of it. This again illus trates the fact that a 5-inch pipe, if large enough to carry the flow, is better than a 6-inch, as the water is deeper in a 5-inch than in a 6-inch pipe, supposing the same quantity of water to be discharged.

Particular attention should be paid to the making of the joint between the clay and the iron pipes. This may be done with one of the

patented devices now on the market, or by cementing just as in the balance of the sewer piping. Leaky joints are a constant menace to the health of the occupants of the building.

Fresh-Air Inlet. When a main trap is used it should always be provided with a fresh-air inlet, usually 4 inches in size, which may be in creased when necessary, for the purpose of re lieving the air-pressure that may accumulate in the system, and to create a current of fresh air throughout the entire piping system. Fig. 3 shows a good method of installing a trap and fresh-air inlet.

It is better to introduce the fresh-air inlet at a point a short distance beyond the trap, as this avoids the possibility of the water-seal becom ing frozen in winter, and also avoids or decreases the evaporation that will occur if the inlet is introduced directly into the hub on top of trap. It is good practice to use a trap with hubs for double vent, as this will allow cleanouts to be placed on both sides of the water-seal, and affords free access to the sewer for cleaning purposes.