CHAPTER VI

Plumbing

Purpose and Requisites for House Plumbing.—A system of house plumbing presupposes the existence of a street sewer, and a water-supply distribution within the house. While the former is not absolutely essential, as a house may have a system of plumbing without there being a sewer in the street, still in the water-carriage system of disposal of sewage the street sewer is the outlet for the various waste and excrementitious matter of the house. The house-water distribution serves for the purpose of flushing and cleaning the various pipes in the house plumbing.

The purposes of house plumbing are: (1) to get rid of all excreta and waste water; (2) to prevent any foreign matter and gases in the sewer from entering the house through the pipes; and (3) to dilute the air in the pipes so as to make all deleterious gases therein innocuous.

To accomplish these results, house plumbing demands the following requisites:

(1) Receptacles for collecting the waste and excreta. These receptacles, or plumbing fixtures, must be adequate for the purpose, small, noncorrosive, self-cleansing, well flushed, accessible, and so constructed as to easily dispose of their contents.

(2) Separate Vertical Pipes for sewage proper, for waste water, and for rain water; upright, direct, straight, noncorrosive, water- and gas-tight, well flushed, and ventilated.

(3) Short, direct, clean, well-flushed, gas-tight branch pipes to connect receptacles with vertical pipes.

(4) Disconnection of the house sewer from the house pipes by the main trap on house drain, and disconnection of house from the house pipes by traps on all fixtures.

(5) Ventilation of the whole system by the fresh-air inlet, vent pipes, and the extension of all vertical pipes.

Definitions.—The House Drain is the horizontal main pipe receiving all waste water and sewage from the vertical pipes, and conducting them outside of the foundation walls, where it joins the house sewer.

The Soil Pipe is the vertical pipe or pipes receiving sewage matter from the water-closets in the house.

The Main Waste Pipe is the pipe receiving waste water from any fixtures except the water-closets.

Branch Soil and Waste Pipes are the short pipes between the fixtures in the house and the main soil and waste pipes.

Traps are bends in pipes, so constructed as to hold a certain volume of water, called the water seal; this water seal serves as a barrier to prevent air and gases from the sewer from entering the house.

Vent Pipes are the special pipes to which the traps or fixtures are connected by short-branch vent pipes, and serve to ventilate the air in the pipes, and prevent siphonage.

The Rain Leader is the pipe receiving rain and storm water from the roof of the house.

Materials Used for Plumbing Pipes.—The materials from which the different pipes used in house plumbing are made differ according to the use of each pipe, its position, size, etc. The following materials are used: cement, vitrified pipe, lead; cast, wrought, and galvanized iron; brass, steel, nickel, sheet metal, etc.

Cement and Vitrified Pipes are used for the manufacture of street and house sewers. In some places vitrified pipe is used for house drains, but in most cities this is strongly objected to; and in New York City no earthenware pipes are permitted within the house. The objection to earthenware pipes is that they are not strong enough for the purpose, break easily, and cannot be made gas-tight.

Lead Pipe is used for all branch waste pipes and short lengths of water pipes. The advantage of lead pipes is that they can be easily bent and shaped, hence their use for traps and connections. The disadvantage of lead for pipes is the softness of the material, which is easily broken into by nails, gnawed through by rats, etc.

Brass, Nickel, Steel, and other such materials are used in the manufacture of expensive plumbing, but are not commonly employed.

Sheet Metal and Galvanized Iron are used for rain leaders, refrigerator pipes, etc.

Wrought Iron is used in the so-called Durham system of plumbing. Wrought iron is very strong; the sections of pipe are twenty feet long, the connections are made by screw joints, and a system of house plumbing made of this material is very durable, unyielding, strong, and perfectly gas-tight. The objections to wrought iron for plumbing pipes are that the pipes cannot be readily repaired and that it is too expensive.

Cast Iron is the material universally used for all vertical and horizontal pipes in the house. There are two kinds of cast-iron pipes manufactured for plumbing uses, the "standard and the extra heavy."

The following are the relative weights of each:

	Standard.	Extra Heavy.
2-inch pipe,	4 lbs. per foot	51/2 lbs.
3 " "	6 " " "	91/2 "
4 " "	9 " " "	13 "
5 " "	12 " " "	17 "
6 " "	15 " " "	20 "
7 " "	20 " " "	27 "
8 " "	25 " " "	331/2 "

The light-weight pipe, though extensively used by plumbers, is generally prohibited by most municipalities, as it is not strong enough for the purpose, and it is difficult to make a gas-tight joint with these pipes without breaking them.

Cast-iron pipes are made in lengths of five feet each, with an enlargement on one end of the pipe, called the "hub" or "socket," into which the other, or "spigot," end is fitted. All cast-iron pipe must be straight, sound, cylindrical and smooth, free from sand holes, cracks, and other defects, and of a uniform thickness.

The thickness of cast-iron pipes should be as follows:

2-inch pipe,	5/16 inches thick
3 " "	" " "
4 " "	3/8 " "
5 " "	7/16 " "
6 " "	1/2 " "

Cast-iron pipes are sometimes coated by dipping into hot tar, or by some other process. Tar coating is, however, not allowed in New York, because it conceals the sand holes and other flaws in the pipes.

Joints and Connections.—To facilitate connections of cast-iron pipes, short and convenient forms and fittings are cast. Some of these connections are named according to their shape, such as L, T, Y, etc.

Fig. 16.

DIFFERENT FORMS AND FITTINGS.

Iron Pipe is joined to Iron Pipe by lead-calked joints. These joints are made as follows: the spigot end of one pipe is inserted into the enlarged end, or the "hub," of the next pipe. The space between the spigot and hub is half filled with oakum or dry hemp. The remaining space is filled with hot molten lead, which, on cooling, is well rammed and calked in by special tools made for the purpose. To make a good, gas-tight, lead-calked joint, experience and skill are necessary. The ring of lead joining the two lengths of pipe must be from 1 to 2 inches deep, and from 1/2 to 3/4 of an inch thick; 12 ounces of lead must be used at each joint for each inch in the diameter of the pipe. Iron pipes are sometimes connected by means of so-called rust joints. Instead of lead, the space between the socket and spigot is filled in with an iron cement consisting of 98 parts of cast-iron borings, 1 part of flowers of sulphur, and 1 part of sal ammoniac.

Fig. 17.

All connections between Lead Pipes and between Lead and Brass or Copper pipes must be made by means of "wiped" solder joints. A wiped joint is made by solder being poured on two ends of the two pipes, the solder being worked about the joint, shaped into an oval lump, and wiped around with a cloth, giving the joint a bulbous form.

All connections between Lead Pipes and Iron Pipes are made by means of brass ferrules. Lead cannot be soldered to iron, so a brass fitting or ferrule is used; it is jointed to the lead pipe by a wiped joint, and to the iron pipe by an ordinary lead-calked joint.

Putty, Cement, and Slip joints should not be tolerated on any pipes.

Fig. 18.

Traps.—We have seen that a trap is a bend in a pipe so constructed as to hold a quantity of water sufficient to interpose a barrier between the sewer and the fixture. There are many and various kinds of traps, some depending on water alone as their "seal," others employing mechanical means, such as balls, valves, lips, also mercury, etc., to assist in the disconnection between the house and sewer ends of the pipe system.

The value of a trap depends: (1) on the depth of its water seal; (2) on the strengths and permanency of the seal; (3) on the diameter and uniformity of the trap; (4) on its simplicity; (5) on its accessibility; and (6) on its self-cleansing character.

The depth of a trap should be about three inches for water-closet traps, and about two inches for sink and other traps.

Traps must not be larger in diameter than the pipe to which they are attached.

The simpler the trap, the better it is.

Traps should be provided with cleanout screw openings, caps, etc., to facilitate cleaning.

The shapes of traps vary, and the number of the various kinds of traps manufactured is very great.

Traps are named according to their use: gully, grease, sediment, intercepting, etc.; according to their shape: D, P, S, V, bell, bottle, pot, globe, etc.; and according to the name of their inventor: Buchan, Cottam, Dodd, Antill, Renk, Hellyer, Croydon, and others too numerous to mention.

The S trap is the best for sink waste pipes; the running trap is the best on house drains.

Fig. 19.

FORMS OF TRAPS.

Fig. 20.

FORMS OF TRAPS.

Loss of Seal by Traps.—The seals of traps are not always secure, and the causes of unsealing of traps are as follows:

(1) Evaporation.—If a fixture in a house is not used for a long time, the water constituting the seal in the trap of the fixture will evaporate; the seal will thus be lost, and ingress of sewer air will result. To guard against evaporation, fixtures must be frequently flushed; and during summer, or at such times as the house is unoccupied and the fixtures not used, the traps are to be filled with oil or glycerin, either of which will serve as an efficient seal.

(2) Momentum.—A sudden flow of water from the fixture may, by the force of its momentum, empty all water in the trap and thus leave it unsealed. To prevent the unsealing of traps by momentum, they must be of a proper size, not less than the waste pipe of the fixture, the seal must be deep, and the trap in a perfectly straight position, as a slight inclination will favor its emptying. Care should also be taken while emptying the fixture to do it slowly so as to preserve the seal.

(3) Capillary Attraction.—If a piece of paper, cotton, thread, hair, etc., remain in the trap, and a part of the paper, etc., projects into the lumen of the pipe, a part of the water will be withdrawn by capillary attraction from the trap and may unseal it. To guard against unsealing of traps by capillary attraction, traps should be of a uniform diameter, without nooks and corners, and of not too large a size, and should also be well flushed, so that nothing but water remains in the trap.

Siphonage and Back Pressure.—The water in the trap, or the "seal," is suspended between two columns of air, that from the fixture to the seal, and from the seal of the trap to the seal of the main trap on house drain. The seal in the trap is therefore not very secure, as it is influenced by any and all currents and agitations of air from both sides, and especially from its distal side. Any heating of the air in the pipes with which the trap is connected, any increase of temperature in the air contents of the vertical pipes with which the trap is connected, and any evolution of gases within those pipes will naturally increase the weight and pressure of the air within them, with the result that the increased pressure will influence the contents of the trap, or the "seal," and may dislodge the seal backward, if the pressure is very great, or, at any rate, may force the foul air from the pipes through the seal of the traps and foul the water therein, thus allowing foul odors to enter the rooms from the traps of the fixtures. This condition, which in practice exists oftener than it is ordinarily thought, is called "back pressure." By "back pressure" is therefore understood the forcing back, or, at least, the fouling, of the water in traps, due to the increased pressure of the air within the pipes back of the traps; the increase in air pressure being due to heating of pipes by the hot water occasionally circulating within them, or by the evolution of gases due to the decomposition of organic matter within the pipes.

Fig. 21.

NON-SYPHONING TRAP.

A condition somewhat similar, but acting in a reverse way, is presented in what is commonly termed "siphonage." Just as well as the seal in traps may be forced back by the increased pressure of the air within the pipes, the same seal may be forced out, pulled out, aspirated, or siphoned out by a sudden withdrawal of a large quantity of air from the pipes with which the trap is connected. Such a sudden withdrawal of large quantities of air is occasioned every time there is a rush of large column of water through the pipes, e. g., when a water-closet or similar fixture is suddenly discharged; the water rushes through the pipes with a great velocity and creates a strong down current of air, with the result that where the down-rushing column passes by a trap, the air in the trap and, later, its seal are aspirated or siphoned out, thus leaving the trap without a seal. By "siphonage" is therefore meant the emptying of the seal in a trap by the aspiration of the water in the trap due to the downward rush of water and air in the pipes with which the trap is connected.

To guard against the loss of seal through siphonage "nonsiphoning" traps have been invented, that is, the traps are so constructed that the seal therein is very large, and the shape of the traps made so that siphonage is difficult. These traps are, however, open to the objection that in the first place they do not prevent the fouling of the seals by back pressure, and in the second place they are not easily cleansable and may retain dirt in their large pockets. The universal method of preventing both siphonage and back pressure is by the system of vent pipes, or what plumbers call "back-air" pipes. Every trap is connected by branches leading from the crown or near the crown of the trap to a main vertical pipe which runs through the house the same as the waste and soil pipes, and which contains nothing but air, which air serves as a medium to be pressed upon by the "back-pressure" air, or to be drawn upon by the siphoning, and thus preventing any agitation and influence upon the seal in the traps; for it is self evident that as long as there is plenty of air at the distal part of the seal, the seal itself will remain uninfluenced by any agitation or condition of the air within the pipes with which the trap is connected.

The vent-pipe system is also an additional means of ventilating the plumbing system of the house, already partly ventilated by the extension of the vertical pipes above the roof and by the fresh-air inlet. The principal objection urged against the installation of the vent-pipe system is the added expense, which is considerable; and plumbers have sought therefore to substitute for the vent pipes various mechanical traps, also nonsiphoning traps. The vent pipes are, however, worth the additional expense, as they are certainly the best means to prevent siphonage and back pressure, and are free from the objections against the cumbersome mechanical traps and the filthy nonsiphoning traps.