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same depth as that of the water in the tank above the level at which the water stands in the bell, the two columns of water balance each other at certain depths. When the depth of the water in the tankb is increased, so that a portion of the air confined in the long leg is forced around the lower bend j of the trap, carrying some of the water with it in its upward rush out of the short leg g, equilibrium is destroyed and the siphon is thereby brought into full action, drawing the water out of the tank until the pipe h is uncovered, when the siphonage is broken by the air admitted to the trap leg c.

A free escape of water from the short leg of the siphon is insured by arranging the discharge mouth to be a little above

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the outlet casting i, as shown. Between the house and the septic tank and from the tank to the filter bed, where the sewage is finally discharged, glazed-tile piping is used, the joints being well cemented.

The sewage discharged from the septic tank is delivered to a disposal field or subsurface filtration bed, where it is absorbed by the soil. The sewage is carried to the absorption bed through a glazed-tile main distributor from which it flows into absorption drains of ordinary field tile, 3 in. in diameter and 1 ft. in length. The field-tile drains are laid in tile gutters, as shown at a, Fig. 3. A space is left

between each section of the tile, the space being protected from the entrance of earth by a loose-fitting cap b. The gutter and cap are made of a larger radius than the outside of the absorption tile, as shown by the illustration, so that practically the whole joint is available for the escape of

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sewage into the ground. The gutter a is laid about 12 in. under the surface of the ground.

The amount of absorption tile required in a reasonably porous soil is about 1 lin. ft. for each gallon of water discharged from the septic tank. If the soil is heavy the length of the tile should be increased to at least 3 ft. for each gallon in the tank. Clayey soil is not suitable for subsurface disposal by filtration.

The fall of the main drain from the tank after reaching a point within 20 ft. of the absorption tiles should not be more than 1 in. in 25 ft. The absorption lines should have a fall of

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not more than 1 in. in 50 ft. If a greater fall is given, the sewage may be carried to the far end of the line, where the sewage is liable to break out at the surface.

In designing the absorption bed, the tile may be run in one continuous line, or a number of short-line branches may be taken off from the main pipe leading from the septic tank, eccentric Y-branch fittings being used as shown in Fig. 4. As a rule, two disposai beds are employed, the deliv. ery piping to each bed being provided with a gate valve, so that the sewage may be directed to either bed, permitting each a period of rest and thus preventing the field from becoming saturated by the sewage.

When it is necessary or desirable to arrange the disposal field on a hillside, the distributing main cannot be laid to fol. low the natural surface of the ground because at each discharge of the siphon the sewage would flow with great force

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directly to the lower end of the bed. This difficulty may be Qvercome, as shown in Fig. 5, by the use of special drops through which the sewage flows with but little fall. The drops are of vitrified pipe, made in one piece, and having hub and spigot ends. Between the drops are placed special drainage branches. These are also vitrified pipe and are made right and left, as the invert of the 3" branch is on the same level as the invert of the pipe itself. Thus water flows as easily into the upper branches that supply the upper rows of field tile as it does into the lower branches, and a uniform distribution of effluent to all the field-tile lines is insured.

WATER SUPPLY AND DISTRIBUTION.

METHODS OF SUPPLY, Street Service. The source of supply of water to a build. ing will depend on prevailing conditions and the location of the building. City buildings are usually supplied from city mains, while country buildings are supplied from wells, lakes, and streams, by means of pumps, hydraulic rams, etc.

House pipes should connect to the mains by corporation stops. A stop-and-waste cock should always be placed under the sidewalk at the curb and also a separate stop-and-waste cock on the service pipe just inside the cellar wall.

If the street pressure is great enough to force water to the top floor of a building, all fixtures are usually supplied with both hot and cold water by street pressure. If the pressure is too low, or the supply intermittent, a tank is placed in the attic to supply the building. If the pressure is too high, it is customary to apply a pressure regulator in the cellar.

The sizes of street service pipes depend chiefly on the street pressure and the size of building to be supplied. The table “Sizes of Street Service Pipes” gives the common practice These pipes should be increased one size if the pressure is low.

SIZES OF STREET SERVICE PIPES.

Class of Building.

Size of Pipe.

Inches.

Single dwellings, two or three stories high
Larger dwellings
Tenement buildings and apartment houses
Hotels and factories.

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Pumps.-The amount of water raised by single-acting pumps is estimated by multiplying the number of strokes which the piston travels in one direction per minute by the volume displaced or traversed by the piston in a single stroke, the supposition being that the water flows into the pump barrel only when the piston ascends. It has been found, however, that the column of water does not cease flowing when the piston descends, and that the amount of water delivered is greater than usually supposed; in some cases, it is nearly double the theoretical amount.

At sea level a column of water 34 ft. high is balanced by the pressure of the atmosphere, but in practice it requires a very good pump to draw to a height of 28 ft.

The height to which hot water can be raised by suction is much less than that of cold water, the height varying with the temperature. This is due to the increased pressure of the vapor. Where possible, the hot water should flow into the pump by gravity. The table “Suction Lifts” gives the theoretical maximum vertical heights of suction pipes for different temperatures.

SUCTION LIFTS.

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In deep-well pumps, the plunger and valves should be below the water. This will make the pump self.priming in case the valves leak. All piston and plunger pumps, particu larly single-action deep-well pumps, should be provided with

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