Sewage Lift.-A device that is commonly used in buildings to raise sewage and discharge it to the street sewer is shown in the preceding illustration, which illustrates the general principles of this apparatus. The sewer is located at a; drainage from the plumbing fixtures in the subbasement and subsoil water has to be removed by an ejector or lift. The main house drain b is run as low as the sewer will allow, and it takes the discharge from all the fixtures above it, and also the roof water. The subbasement main drain c is located just low enough to take the discharge from all the plumbing fixtures located below the sewer level. The lower end of c discharges into the bottom of a cast-iron or wrought-iron receiver d through a check-valve e. A discharge pipe f having a check-valve g located near the receiver delivers the contents of d into the house sewer h, the connection being made on the sewer side of the main drain trap shown. An air compressor i operated by an electric motor j pumps com. pressed air into an air reservoir k through the pipe l. An automatic switch regulator and rheostat are located in a casing m. A pipe connects the regulator with the air receiver. The pressure carried in k is preferably not less than 1 lb. for each foot that the sewage has to be raised. Thus, if the distance X is 15 ft., the pressure in k must be not less than 15 lb. per sq. in., indicated by the gauge shown on top of k. The apparatus will operate with a lower pressure in k, but the time required to discharge the contents of d to the sewer will be much longer and there will be a liability of the discharges from the fixtures in the subbasement filling c before d is empty.

The automatic discharging of d is accomplished by means of three automatic valves n, o, p. The valve n is a hydraulic valve having its inlet connected to the water-supply main q by a pipe, and its outlet connected to the balanced valve p on the vent pipe. These balanced valves work in opposite directions; thus, when the valve n is open, water under street pressure opens the valve o and closes the valve p. This allows compressed air to flow freely into d, press down on the surface of the sewage that has accumulated therein, and thus

force it up through f to the sewer; the vent valve p, being closed, confines the compressed air in d. As soon as the valve n is closed, the water pressure is removed from the balanced valves and they reverse their position; that is, the valve o is shut and p is opened. This action allows the com

pressed air confined in d to escape through the vent pipe r to the vent stack. The pressure inside d then becomes equal to that of the atmosphere, and sewage can flow freely from c to d.

The water valve n is operated by a stem passing down through the top of the receiver, the upper end of the stem being attached to the balance lever on the valve stem and the part inside the receiver being furnished with a float near the top and a submerged bucket at the bottom. When the sewage has risen in d to the level of the float, the stem is raised by the buoyancy of the float and the water valve n is opened, allowing the air pressure to force the sewage from d. The water valve remains open as the tank is emptied until the water-line falls below the submerged bucket, when the weight of this bucket moves the lever of the valve n and shuts off the water from the balanced valve. Thus, it will be seen that the upper float opens the valve n and the submerged bucket closes it. The subsoil water from the foundation drains discharges by gravity through the pipes t, t into the brick sump u, filling this sump outside of the receiver; checkvalves are placed over the mouth of the pipes t, t inside the sump to prevent rats from entering the subsoil drains. Sump water flows through the check-valve v into the receiver as soon as the air pressure is removed from the receiver, because the water-line in the receiver is then lower than the waterline in the sump. This check-valve automatically closes, however, as soon as the sewage in the receiver has reached the level of the water in the sump. The sump should be covered with movable iron plates laid flush with the floor; the valves n, o, p are usually located under these plates and on top of the receiver.

The advantage in having the subsoil water flow into the sump lies in the fact that should the check-valve v leak, the

water in the sump will become slightly polluted with sewage, which can be readily detected by the engineer. If the subsoil drains were connected directly to the tank, this checkvalve might leak sewage back into the subsoil drains without the fact being noticed, and thus saturate the soil under the building with sewage matter, which would be a dangerous condition. Should the check-valve e leak, sewage matter from d will be forced back to c and overflow the subbasement fixtures if the volume of leakage is sufficiently great to fill these lines while the ejector is working.

Presumably the safest attachment that can be used is a sliding gate valve placed close to the check-valve e and another one close to ; both of these should be operated by a rod attached to a plunger that is moved by water pressure from n. Thus, when sewage is being ejected, the gate valve at e and will be closed but will open automatically as soon as the pressure in d is relieved.

The ventilation of the house-drainage system in the subbasement is accomplished by a fresh-air inlet pipe w that connects with the fresh-air inlet pipe w' for the plumbing system on the floors above. The back-vent connects to the fixtures of the subbasement, being connected to the vent stack. In this way thorough ventilation of the subbasement plumbing can be obtained.

Should only one receiver be installed, it is essential to have auxiliary apparatus that will discharge the sewage while the air-pressure sewage lift, or ejector previously described, is undergoing repairs. To accomplish this, it is customary to attach a steam-jet ejector at x on the discharge pipe from the sump. Without this ejector, should the motor, compressor, or switch be shut down, the tank k will lose its pressure and sewage will flood d and the basement fixtures while the repairs are being made to the machine. While these repairs are going on, it is necessary only to open the gate valve on the ejector steam pipe, allowing the steam to flow through the ejector x. This will lift the sewage from the tank d into the street sewer, but will raise the temperature of the sewage presumably about 15 to 20 per cent. When the

sewage has been sucked out by the steam ejector, cold water will be shut off from an automatic valve on the ejector steam pipe, which will, in turn, shut off the steam from the ejector. The steam ejector, therefore, works intermittently as the tank becomes filled with sewage.

The discharge pipe ƒ connects to the sewer side of the main-drain trap to prevent steam accidentally flowing through ƒ and entering the drainage system, which would ruin the joints in the system throughout the building if it were allowed to blow up through the soil and vent stacks.

When two or more receivers are employed, the check-valve on one should be weighted heavier than the other, so that the receiver with the weighted check-valve will take the surplus sewage that backs up in the line while the receiver with the light check-valve is being discharged.

Should an air-pressure sewage lift work too slowly to take the drainage, it is necessary only to increase the pressure in the air tank k. The average job works under a pressure of about 30 to 40 lb. in k, which gives a rapid discharge to the tank.

DISPOSAL OF SEWAGE.

Methods of Disposal.-Sewage from buildings is disposed of chiefly by the following methods: (1) By connection to the street sewer; (2) by cesspools; (3) by direct or indirect discharge to sea, or river, in close proximity to the buildings. The first plan is always adopted in well-regulated cities having a sewer system, and the work is usually done under the supervision of city authorities.

Cesspools. Where the first and third methods cannot be employed, cesspools are commonly used. They should be built water-tight if within 200 ft. of any buildings or within 100 yd. of any well. Fig. 1 shows common practice in cesspool connections. The main drain from the house is continued through the cellar wall, a trap a and fresh-air inlet b being placed outside; either a vitrified or cast-iron sewer pipe c connects with the cesspool d; and a cesspool vent e is

run up the trunk of a tree. A tight-fitting manhole cover should be provided for access to the cesspool d.

The size of a cesspool must be determined by the approximate amount of discharge. The least size for a 7- or 8-room house is from 6 to 8 ft. in diameter, and from 10 to 12 ft. deep. The following rule is in common use; For a house with 6 rooms or less, make the cesspool 6 ft. in diameter; for a 7-room house, 7 ft.; increase the diameter 6 in. for each additional room up to 10 rooms; then 3 in. for each additional room up to 20; then 14 in. for each additional room. The general depth is from 10 to 15 ft. The cesspool should be brick-lined, domed over, and, if possible, provided with an overflow. Septic Tank System.

FIG. 1.

Fig. 2 shows a septic tank having two parts: A receiving or settling chamber a and a discharge chamber b, in which an automatic siphon is placed. The siphon consists of a discharging limb, or deep-seal trap, c and an intake bell d held securely in place by its own weight over the long leg of the siphon. The sewage flows into the settling chamber through the pipe e, the liquid overflowing into the discharge chamber b through the deeply trapped pipe f. The water gradually rises into the bell d, shutting air in the long leg of the siphon. As the water rises in the tank b, the pressure on the air confined in the long leg of the siphon gradually forces the water therein to the level shown, when the air is ready to escape around the lower bend j of the trap. The distance between the water levels in the two legs of the trap is the same as the distance between the level of the water in the tank b and the level of the water within the bell d. The column of water in the short leg g having the