Materials

No pipes should be used which are not nearly cylindrical, a variation of over one-fourth of an inch in the different diameters of a 6-inch pipe being enough to condemn it.

The pipes should not have bells or hubs attached, as is now generally done, but should be formed in simple cylinders, the joints being covered by loose rings or collars of the same material, without glazing, to be broken in three or more pieces when applied.

The thickness should be uniform and not less than 5/8 and 3/4-inch for 5-inch and 6-inch pipe, respectively.

The glazing should be " salt glazing" and not "slip " or clay glazing, and should extend throughout the whole interior, but should be omitted on the collars and on the outside of pipes for one and one-half inches at either end of the pieces. If the ends are glazed outside the cement used at the joints does not adhere well, and the joint may be leaky, even with good cement and put together with the best of care.

The clay of which they are made should, of course, be of good quality and well burned. Less trouble, however, is found in practice with the kind of clay than with the results of careless molding, such as oval, crooked pipes, with glazing applied all over the ends, for no better reason than because it costs some trouble to omit the glazing there, although it is a positive injury.

The cement should be of any good brand, of fair hydraulic properties, fine and freshly ground, and carefully mixed with not over its own bulk of clean, sharp sand. In all places where the sand is not clean (it should not soil the hands when rubbed between them) it should be washed thoroughly in a bed not over six inches deep with a copious flow of water, stirring the sand and water quickly with a hoe and allowing all the loam and clay to be carried off, till the water ceases to look muddy. The sand should be then dried and mixed thoroughly with the cement before applying any water. When wetting it for use, no more water should be used than is absolutely necessary to render the mortar plastic.

It should be wetted only in small quantities for immediate use. All lots left over an interval of half an hour, long enough to stiffen and begin to " set," should be thrown away and not " tempered up " as is generally done for indiscriminate use. Cement when rewetted after a partial set is sure to shrink and crack when it hardens, and is worthless for pipe-laying.

The ends of pipes and insides of collars should be wetted in warm weather before applying the mortar to these surfaces. If applied dry, the porous pipe absorbs the water so quickly from the mortar that it never hardens properly, and does not adhere to the pipe.

Workmanship

Pipe should be laid with such good alignment that the inspector can see through every section, like a gun-barrel, from one manhole or lamp hole to another, or from house to sewer. This can readily be done with very little extra cost, if pains be taken to pursue proper methods.

Every piece of pipe should be bedded in cement-mortar through its middle portion as well as at its ends, leaving no voids longer than the inside diameter of the pipe between these bearings. The lower half of the pipe should be carefully aligned with its neighbor, by applying a straight-edge inside when bedding, to avoid offset at the joints, leaving slight inaccuracies in form to be developed at the top of the pipe, which is rarely wetted by the flow.

Through every piece of pipe as laid should be passed a cord, made fast where starting, and extending through every section of pipe laid, by means of which a wiper, or rubber disk between two smaller wooden ones, can be pulled through the whole section before leaving it for a night. Of course, the mason is expected to see that every joint is clean as laid, but human nature is fallible, and cannot be trusted to remember this, the consequence of such neglect being often a total failure of the drain.

Every section should be covered about three inches with fine earth, and tested by some two or three feet of water-pressure, when the defects will be seen, and may be remedied before filling the trench. The best masons will be astonished to see how many leaky joints they make unawares, and which may never be detected in any way but this.

The back-filling should be applied with care, packing the material around the pipes without moving them on their beds even a hair's breadth. The trench may be puddled with water if it is at hand, taking care not to wash the cement when applying it.

No good drain can be laid on a yielding foundation. No matter what the material may be, it will break and make leaks when settlement occurs, for though the drain itself is light, the material over it is heavy, and crowds it down as it settles. All drains on newly-filled land should be treated as temporary works, to be replaced when the settlement is finished.

There may be places where the difficulty of getting proper workmanship and proper materials will render it advisable to use iron pipe between the house and sewer, and New York and Brooklyn may be such places; but wherever it is used, it is subject to corrosion, and becomes so incrusted with tubercles inside, after a score of years, that it cannot serve as a self-cleansing sewer. It is necessarily always foul when incumbered with rust, for the flow of water does not cleanse it. It is then a sewer of deposit, open to all the objections that attach to cesspools or other foul sewers.

When used inside of houses it is accessible, and can therefore be readily inspected, both inside and outside, and readily repaired or replaced in case of need. But if buried in the ground, it is out of sight and out of mind, and should therefore be made of imperishable materials.