122. Waste pipes are those pipes which convey waste water from any or all of the fixtures in a building except the water closets. If their length exceeds 4 or 5 feet, they are usually made of cast iron. A general custom in the United States is to make all stacks or vertical lines of pipes of cast iron, with spigot and socket joints.

The branch pipes through which the fixtures discharge into the stack are made of lead, if short. If more than 5 feet in length, and without too many changes in direction, an iron-pipe branch is generally carried to a point suitable for a lead-pipe connection to the fixture. The reason why lead waste-pipe connections are generally made to the fixtures is because the lead can be bent to suit any position, and forms a pliable connection which will not break the fixture owing to a small settlement of the pipes or building. But it must be thoroughly supported to prevent it from sagging. The pipe should be inclined towards the stack to secure a rapid flow of water. The Y branch of the stack should be located as low down as practicable, and the waste pipe may be run between the floorbeams.

123. The waste pipes from baths and basins should be connected directly to the soil-pipe stack, and should not be connected to the water-closet branch.

Waste pipes of lead should not be wiped or connected at right angles, but always at a larger angle, which will favor the passage of matter towards the outlet.

Care must be taken that the water which is being discharged from one waste pipe does not back up into some other pipe, because it will form deposits in, and choke up, the other pipe.

The waste pipes from safes should not be connected to a soil or vent stack. They should discharge openly at some conspicuous place where the least indication of a leak will be quickly made apparent.

The waste pipe from a refrigerator should not, under any circumstances, be connected to a soil or vent pipe, but should discharge at some clean place.

The overflow from a house tank, or cistern, should not be discharged into a drain, or soil, pipe, but should discharge openly in a place where the overflow will be seen.

Urinal waste pipes should be as short as possible. They should be well supplied with screw-caps, to afford easy access to the pipe for cleaning-out purposes, as a thick slime accumulates in such pipes.

124. The proper sizes of waste pipes for various uses are as follows:

Bath waste, 1 1/2 inches to 2 inches'in diameter.

Basin waste, 1 1/4 inches to 1 1/2 inches in diameter.

Urinal waste, 1 1/4 inches to 2 inches in diameter.

Wash tubs, 1 1/2 inches branch and 2 inches trap for three tubs, the trap taking one tub.

Sink waste, 1 1/2 inches to 2 inches in diameter.

Pantry sink waste, 1 1/2 inches in diameter.

Safe waste, 1 inch to 1 1/2 inches in diameter.

Water-closet trap, 3 1/4 inches to 3 1/2 inches in diameter.

Soil-pipe stack, 4 inches or 5 inches in diameter.

Branch to closet from soil-pipe stack, 4 inches in diameter.

Sink and tub stack, 2 inches to 3 inches in diameter.