Where should clean-outs be placed?

At each right angle turn, at the end of each horizontal line, and at intermediate points in long lines of horizontal pipe.

What is the least fall that should be given soil pipe?

One-fourth inch per foot.

Why should Y branches be used in preference to Ts?

Y branches permit the sewage to pass through without interfering with its momentum as Ts do, thus giving a much better wash to the pipe with less liability to choke up.

How far should soil pipe be carried from the house before entering the earthen drain?

It should be carried ten feet from the inside of the wall, or two lengths. Where the drain pipe is carried nearer the house, the sewage is liable to leak out and work back into the cellar.

What should be done when a stack opens near a window?

It should be carried five feet above the window.

Why should caps not be used on ends of soil pipe above the roof?

By diminishing the size of the opening, they are liable in cold weather to close up with hoar frost.

Is it right or wrong to enter a line of pipe into the main drain on the sewer side of the main trap?

It is wrong, for by such means the sewer gas may be transmitted directly into the house.

What benefit is derived from carrying the main stack through the roof?

It relieves the pressure of the sewer gas upon the trap seals, allowing a free circulation through the drainage and vent systems of the house.

What advantage is gained by entering the rain leaders into the soil pipe?

The rain during a storm acts as a heavy flush and aids in keeping the drain clean.

What is the relative size of waste and vent pipes?

They should usually be the same, excepting in the case of the water closet.

Why should soil pipe be increased to four inches before going through the roof?

During the cold weather pipes of less diameter than four inches are liable to become filled with frost.

Why should all lead pipe joints on the drainage system be wiped?

The wiped joint is much stronger and more perfect than the cup or overcast joint.

Under what conditions should conductor pipe from the roof be allowed to enter the house drain?

Where there is no house trap the rain leaders should be independently trapped. Where there is a house trap it is not necessary to trap them separately so long as they enter the main drain on the house side of the main trap.

Describe the cellar drainage system.

This drainage is used in cellars where the bottom is moist. Under the cement cellar bottom, and completely around the cellar, is laid a line of porous die with loose joints, which drains into a well formed in the cement, water leaching in through the joints and through the tile. The hub of a cast iron trap is cemented into the bottom of the well, and the water collecting there, carried into the main drain. Where there is no main trap there should be a trap screw to close the opening in dry weather.