Safe-wastes and the overflow-pipes of tanks and cisterns may be connected with the soil or waste pipe. When they are, they are usually trapped. It will often be found that the traps are empty and useless, so that offensive gases escape from the pipes. With tank-overflow pipes this is generally the case. Safe-waste traps are sometimes provided with small feed-pipes, intended to discharge water into them every time the fixtures are used. It will often be found, however, if the end of the feed-pipe is pulled up out of the waste, that no water runs through it, and it is useless, sometimes because it is too small and is choked with dust and sediment, and sometimes because it is wrongly attached to the source of supply. Safe-wastes, discharging into the kitchen or cellar, may convey to the rooms odors of cooking or of articles stored in the cellar (onions, turnips, etc.), or from the servants’ water-closet, which is often offensive. If urine or other offensive liquids from leakage flow through them, the upward currents of air will be impregnated with odors from the filth that has clung to the pipe long after the leak has been repaired. In any event these safe-wastes constitute a direct communication between different rooms of a house, which is not always desirable. It is better to do without them. They are rarely of any use. If required, however, they should either be trapped under the safe, and means taken to insure a constant water-seal, or they may be closed by a piece of paper pasted over the lower opening, which will prevent the entrance of any odors from cellar or kitchen, but will give way in case of leakage. The safe-wastes of water-closets often discharge into the trap of the water-closet. This is a bad plan, because, if there is an obstruction in the trap, the safe-waste is, of course, useless. If offensive odors are traced to safe-wastes, the openings had better be sealed. If overflow-pipes are the source, they must be disconnected from the soil or waste pipe and made to discharge elsewhere (e. g., into some sink or water-closet).
(d.) Traps.—If two traps are so arranged that the air is compressed between them by an oncoming rush of water, the trap containing the shallowest water-seal will be forced, and a certain amount of air will escape through it from the interior of the pipe. This result is due to “cushioning,” as it is called, and is illustrated in Fig. 29. Such a fault is to be remedied by connecting the crown of one of the traps with a ventilating-pipe, so that any pressure of the kind is immediately relieved without disturbing the seal of the trap.
If there are two traps on the same line of pipe (Fig. 30), so that a part of the interior of the pipe is cut off from the external air in both directions, it becomes “air-bound,” and one of two results will follow, viz.: water discharged into the fixture above the higher trap will remain in the bowl and not run down, on account of the compression of air between the traps; or, if it does run out of the fixture, it will displace an equivalent bulk of foul air, which will bubble up through the upper trap and cause offensive odors. In such a case, the lower trap should be removed.
If two or more waste-pipes (as in sets of tubs, in sinks, and often in urinals) are provided with but one trap for all (Fig. 31), there will be a constant current of air along the pipes, sometimes emerging from one opening and sometimes from another. This air will be contaminated by the filth that lines the pipes, and will often be quite offensive. In such cases, each waste-pipe should be independently trapped, or (as in the case of bath-tubs or urinals) the overflow-pipe should be connected with the trap of the waste-pipe below the water-seal, as in Fig. 25.
When a body of water sufficiently large to nearly fill a pipe is discharged into it, it drags air along with it, and exhausts the air in all branch-pipes to a greater or less extent. When this exhaustion amounts to a diminution of the pressure in the pipe of about 1/350, the water in an ordinary trap (with a one-inch seal) will be forced out of it by the pressure of the external atmosphere, or in other words will be sucked out of the trap into the pipe, leaving no water-seal in the trap, and, therefore, allowing free exit for sewer-air. This effect is known as the “siphoning” of the trap, and is most likely to occur when the main pipe is not open at its upper extremity (is not ventilated), and when the branch wastes are of the same size with the main one. This fault is remedied by the ventilation of the traps, and of the main pipes, as described in the regulations above quoted (17 and 33).
2. To defects in the pipes. (a.) Drains.—Bad odors in cellars often come from broken earthenware or tile drains, cracked by settling, or from rat-holes in cemented drains. Earthenware or brick drains inside a house should be replaced by iron ones.
(b.) Joints.—Cement or putty joints are often cracked. Water-closets sometimes become loosened from the floor and leak fluids and gases. The covers of hand-holes of traps sometimes get loose and leak gas. Sometimes trap-screws, instead of being at the bottom of the trap, where they are covered by water, are at the top; if these are loose, gases may escape. All such defects should be repaired.
(c.) Pipes.—Both lead and iron pipes are corroded and in time perforated by sewer-air. Such corrosion is most likely to occur at points where gases come in contact with a dry part of the pipe, viz., at the crowns or domes of traps, and in ventilating-pipes. For this reason, ventilating-pipes should never be made of thin iron (galvanized iron), and should always be protected by a tar-coating. The crowns of lead traps (especially of water-closets) are often bitten into by rats in search of water. In all cases when the crown of a trap is perforated, there is rarely any leakage of fluid to indicate it, but offensive gases escape. All corroded traps and pipes should be replaced by new ones, and not patched up. Holes in iron pipes may be closed by iron bands surrounding the pipe, and fastened with red-lead putty and screw-bolts (Fig. 32). A new joint may be made by means of a saddle-hub (Fig. 33) carefully secured in a similar manner. Lead pipes are sometimes protected against rats by being encircled by tin, or packed in pounded glass.
3. To carelessness. (a.) Evaporation.—If fixtures are not in constant use, the water soon evaporates from the traps and gives exit to sewer-air. This often happens in warm weather, and when a house is vacant for a time. To prevent evaporation, a little oil may be poured into the trap, to protect the surface of the water-seal, or it may be made the special duty of a servant to keep the traps full of water when the fixtures are not in use.
(b.) Dirt.—The inside of a pipe often becomes coated with slime, consisting largely of grease, especially in kitchens. This filthy lining rapidly decomposes, and that portion above the trap may give out bad odors. The pipes may be cleansed with a strong hot solution of soda.
Examination of House-Drainage.
If the object of an examination is to determine whether the drainage is planned and constructed in accordance with the best methods of the day, each point referred to in the above regulations should be carefully investigated.
If the object is to determine the source of offensive odors, or if there has been sickness in the house of such a character as to indicate possible defects in the plumbing, the several sources of bad odors just enumerated should each be carefully inquired into. A few additional suggestions as to the method of examination will not be out of place.
It will be found much easier to determine the direction, number, and situation of the main lines of pipe, if the examination is begun at the roof and continued downward. If a beginning is made in the cellar, confusion results.
“Cushioning” is determined by causing the discharge of a considerable mass of water (as from a bath-tub or water-closet) into the main pipe, at some distance above the suspected fixture. If there is a regurgitation in the fixture under observation, there is certainly an obstruction in the pipe at some point below the fixture. If the obstruction is caused by something lodged in the pipe, the back-flow in the fixture will be a steady one, because there will be some leakage through the obstruction, while if it is due to compressed air, which is elastic, the regurgitation will be by spurts, and the water in the trap may even be thrown up to a considerable height.
“Siphoning” is also determined by filling the pipe with water in the manner just explained. If the trap of the fixture under observation is emptied by siphoning, a sucking or gurgling noise will be heard in it, and a flame held over the outlet of the fixture will be drawn downward by the inward current of air.
One trap to several pipes (when it is suspected but not certainly known because the trap is out of sight) may be detected by the fact that there will always be a current of air in one direction or the other through such pipes, and more or less odor will escape. If the back of the hand is wet, it becomes very sensitive to such a current, and by holding alternately the palm and the back of the hand, or even of the forefinger (wet), over an opening, the existence and direction of such a current can be easily determined. If the odors are from such a source, it can then be made evident by covering all the outlets but one with wet paper, so as to prevent the air-currents, when the odors will temporarily disappear.
If a trap is accessible, it is easy to determine whether its water-seal is preserved or not by tapping it from top to bottom with some metallic substance, when the difference in sound will indicate the exact level of the water inside.
Those parts of the plumbing which are not accessible to inspection must be examined by introducing into the pipes some strong-smelling substance, which will indicate defects by its escape through them into the house. Oil of peppermint is often used for this purpose.
The Peppermint-Test.
For testing the pipes of an ordinary dwelling, one ounce of the oil of peppermint is sufficient. For a large building more may be needed. The drug costs from twenty-five to seventy-five cents an ounce, according to its quality and the place where it is bought.
It is best to introduce the oil into the pipes from outside the house, if possible, so that the odor which inevitably attends the process may be dissipated in the external air. The object being to ascertain the location of defects in the pipes inside the house, the examiner must feel certain, if he detects the odor of peppermint anywhere, that the vapor has come to him from inside the pipes, and not from the outside. If the ventilating-pipes are so constructed that the oil can not be poured in from the roof, then it must be poured into some basin or water-closet in the upper portion of the house. The peppermint should first be mingled with a pailful of hot water to promote rapid volatilization, and poured slowly down the pipe. After it is poured down, the openings at the upper extremities of the pipes should be closed, so that the pressure of the vapor inside the pipes may not be relieved in that direction. If the odor of peppermint, thus introduced with the precautions mentioned below, is perceived anywhere in the house, it is an indication that there is an opening in some pipe, through which sewer-air may escape. This opening may be a defect, or it may be due to siphoning of traps, or to faults of original construction. There will not usually be much difficulty in locating it with considerable exactness.
Special Precautions.
The peppermint should be kept on the roof, or on a window-sill outside the house, until needed, for it is so volatile that the vapor escapes through the cork, and if the odor gets into the house in this way, it will vitiate the examination.
The person who pours the peppermint should remain on the roof or in the room where he does it, with the doors closed, until the examination is complete, for the odor will cling to his clothing and follow him wherever he goes for an hour or more.
Additional Remarks.
If bad odors have been noticed, and no defect can be found in the ways above mentioned, they may be due to decaying animal matter (dead rats, etc.), or (in the city) to defects in the plumbing of the adjoining house, offensive gases from which may penetrate the wall.
The source of bad odors need not necessarily be in the immediate vicinity of the place where they are noticed, for the walls of buildings are full of channels and openings, through which offensive gases may be carried by currents of air, so as to emerge at a considerable distance from their origin. Thus, in winter, they are apt to be most noticeable near a fire.
SUMMARY OF THE BEST METHODS OF DRAINAGE.
For houses where there are public sewers: water-carriage.
For country houses, if isolated from sewers, and where expense is no objection: water-carriage with subsoil drainage.
In villages and small towns, without sewers: subsoil drainage (for slops), and pails (for excreta), frequently removed by proper officers.
For farm-houses: subsoil drainage for slops, and a movable tank, with dry earth disinfection, for excreta.
For sea-side houses, isolated: if there is vegetation, subsoil drainage for slops, and earth-closets.
For sea-side villages: subsoil drainage and the pail system.
For sea-side houses, where there is no vegetation: for excreta, earth-closets or a movable iron tank, with dry-earth disinfection; for slops, a water-tight cesspool, with arrangements for emptying its contents into the sea when the tide is ebbing.
How to prevent contamination of the air from the ground.
Have the house separated from the soil on which it is built by a layer of asphalt between two layers of cement, extending over the whole cellar-floor, through the foundation-walls and up above the point where the ground touches the walls outside. Or have the house built without a cellar, and with perforated underpinning, so as to allow a free circulation of air underneath it. The subsoil should also be drained by tiles laid at least a foot lower than the cellar-bottom.
The cold-air boxes of furnaces should draw their supply from the external air. It is advisable to have a thin layer of cotton held in place by wire gauze to filter the air as it enters them.