Plate 31 shows the general form of the drainage piping in the cellar or basement. Many of the features which appear have been taken up under preceding plates, such as main trap and fresh-air inlet, cellar and subsoil drainage, etc., and will not be again considered here.
Before taking up the consideration of the above subject, it will be well to clearly define the terms house drain and house sewer, concerning which there is often some confusion.
The house drain is that portion of the horizontal piping of the drainage system of any building into which all the soil and waste pipes, whether vertical or horizontal, but inside the building, ultimately discharge. The house drain extends through the foundation wall.
Plate XXXI. Construction Of Cellar Piping -The House Drain, House Sewer, Etc
The house sewer is a continuation of the main drain, from the point where the latter ends, to its connection into the sewer or cesspool.
The house drain and sewer, under any ordinary circumstances, should serve but the one building, it being entirely wrong to connect the sewage from any building into the house drain or house sewer of another building. The drainage system of each building should be entirely distinct and separate from all other buildings.
It sometimes occurs in the large cities, where buildings of mammoth proportions are erected, that in order to properly care for the vast amount of sewage collected over large areas and from many floors, it is necessary to make use of two house drains and sewers for different sections of the building, in which case the two systems are entirely separate. More than two house drains and sewers are rarely required. The running of the house drain, whether overhead or underground, is determined largely by the prevailing usages of different towns and cities. For instance, the prevailing construction of some cities is flat houses, in which all plumbing fixtures will be found on the several floors, and none in the basement or cellar, under which conditions the house drain may be run overhead.
On the other hand, the prevailing dwelling houses of another city may have two or three single flats, the laundry tubs for the several flats being placed in the cellar, which necessitates running the house drain underground. The house drain should be of extra-heavy iron pipe, and should be carried to a point 10 ft. from the inner face of the cellar wall. This means that two full lengths of soil pipe are to be used in running from the foundation wall to the house sewer.
The reason for this requirement is the danger of broken earthenware pipe and fittings and cement joints, close to the foundation wall, with the consequent danger of the leeching of escaping sewage through the foundation walls into the cellar. When laid underground, nothing but extra-heavy tarred cast-iron pipe should be used, whether it be the house drain or branches from it. This is required for the reason that uncoated cast-iron pipe is in time destroyed by galvanic action when laid underground, and wrought iron and steel pipe suffers in the same way, but to a far greater extent. On no account should earthenware pipe enter the cellar. The best method of making the connection at the main trap is shown in Fig. A, Plate 25, as the use of an end cleanout is thus allowed, which will control the straight line out into the house sewer in the event of stoppage. If the house drain through the foundation wall cannot be laid low enough for the main trap to discharge into the Y from above, the Y may be used lying on its side.
All entrances into the house drain, or into any horizontal soil or waste branch, should be made through Y-branches or Y-branches and bends.
Into the house drain all floor drains, cellar drains, etc., should be connected.
In the case of rain leaders, they should be connected into the house drain when brought inside the basement or cellar, but may also be run outside the foundation walls and entered into the house sewer. If, however, there is a separate public system for surface sewage, clear waste, such as coming from floor and yard drains, rain leaders, subsoil drainage, etc., should be connected into the house drain of the surface sewage system.
The matter of the use of the main trap is generally determined by plumbing ordinance. The practice is varied, some cities demanding its use, others prohibiting it, and still others making its use optional. When the main trap is used, however, all connections into the main drain should be made on the house side of the trap.
The objection to the use of a main trap, due to the forcing of its seal, has caused a trial of two main traps on the house drain. The use of two traps, however, has not been taken up to any extent.
Whenever two traps have been used, the fresh-air inlet has been taken off on the house side of the trap farthest from the sewer, and in order that there shall be no air lock between the two traps, a vent was taken off a fitting placed between the two traps. The idea of this arrangement was that, in case back pressure from the. sewer was sufficient to force the seal of the first trap, the seal of the second trap could never be forced because of the vent between the two traps, and in this way sewer gas would be prevented from entering the house-drainage system. -An objection advanced against the use of a single main trap is that it impedes the free outflow of sewage and is subject to stoppage.
The use of two traps would certainly increase these troubles, and their use would seem to be inadvisable. As already stated, simplicity rather than complexity is to be desired in all parts of the plumbing system, and especially at such a point as the main trap, where serious trouble affects the entire system.
As stated above, the house sewer begins at the point where the house drain ends, which is generally 10 ft. from the inside face of the foundation wall, although some plumbing ordinances make this distance only 5 ft. In general, the house sewer is constructed of vitrified earthen pipe, and should be one size larger than the house drain. If the house drain is 4 in. in diameter, the house sewer should be 5 in.
All pipe that is buried deep underground, and therefore not easily accessible, should be of larger size than for the same line when running above ground, whether the pipe be used for drainage or supply purposes. When the house sewer is laid in made ground, or in ground that has been filled in, or is in danger of destruction from roots of trees or from the action of frost, earthenware pipe should never be used. Under these conditions nothing but extra-heavy tarred cast-iron pipe should be used, laid with caulked lead joints, but not with cement joints. When the house sewer must of necessity run close to any cistern, or any source of water supply, it should be constructed of cast-iron pipe.
Joints on the earthen pipe of house sewers should be given as careful attention as joints on any other part of the plumbing system, although this work is often constructed in a most careless manner. Portland cement of the best quality should be used, three parts of clean sand to one part of Portland cement.
The opening between the spigot and the hub should be entirely filled with cement, and whatever cement has squeezed out into the interior of the pipe should be cleaned off and removed before the next length or fitting is laid. A lath is convenient for cutting off the superfluous cement. A stronger and better joint may be made by caulking a ring of oakum into the hub before the cement is put in.
The spigot end should be inserted into the hub so that the thickness of the cement will be uniform around the circumference. Depressions should be cut into the bottom of the trench for the hubs to set into, thus allowing the pipe to rest firmly on its entire length rather than on the hubs only. The bottom of the trench should have a uniform grade of not less than 2 ft. in 100 ft., and more where possible, and in long lines of trench work it becomes almost necessary to have the grade laid out by an engineer in order that the work may be done properly. This is especially true when the total pitch for the entire length is barely sufficient, and must be distributed evenly.
Before trenches are filled in, the earth around pipes should be thoroughly rammed, and no pipe, whether water or drainage, should be covered until inspected by the proper official. Changes in direction of the house sewer, entrances into it of rain leaders, etc., should be done under the same general rules regulating like work in connection with the house drain.
When rain leaders connect into the house drain or house sewer, it should be seen to that these two lines are of sufficient size to handle the large volume of rain water entering them during severe storms. The amount of water which a line of pipe can safely be depended upon to carry depends largely on the grade at which the pipe is laid.
The connection of the house sewer into the street sewer should be made as shown in Plate 31, that is, by the use of a Y-branch on the main sewer and a bend on the house sewer.
This is more satisfactory than entering a tee, just as it is on the house-drainage system. When the street sewer and house sewer are of such levels that a proper grade can be secured, the house sewer should enter the main street sewer above the center of the arch of the latter.