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FIG. 11.-INSIDE VIEW OF L. R. S. PRIVY (STILES AND LUMSDEN, 1911). The liquefying tank may be of wood (zinc lined or heavily tarred) or of iron.






This has all the advantages had by the barrels and will last indefinitely. It will cost more, perhaps, in the beginning than barrels, but in the end be cheaper. (Ferrell, 1911.)

BILL OF MATERIAL AND DIRECTIONS FOR CONSTRUCTING PERMANENT CONCRETE TANKS. [By John A. Ferrell, M. D., assistant secretary for hookworm disease to North Carolina Board of Health, Raleigh, N. C.]

To construct the concrete tank as a modification of the L. R. S barrel privy (fig. 13), excavate a pit at the site selected for the privy 3 feet 2 inches deep and slightly larger than the outside dimensions of the tank. The bottom of the excavation should be perfectly level to receive the concrete forming the floor for the tank.

Build the forms to the dimensions given on drawings, the outer form to be 3 feet wide by 5 feet 6 inches long, inside measurements. The two inner forms should be 2 feet square, outside measurements. When the two inner forms are set inside of the outer form there should be 6 inches left all around and between the inner forms, so that when filled all walls and the partition between the tanks will be 6 inches thick.

Mix the concrete in the proportions 1 part Portland cement, 2 parts clean sharp sand, and 4 parts clean creek or bank gravel free from loam or other foreign matter, or crushed stone of a size to pass a 4-inch mesh screen. In mixing the materials the sand should be first spread in a mortar box. or on a tight platform or mixing board, and the cement spread on top of the sand; the sand and cement should first be mixed dry, and then wet and mixed until it shows a uniform color. The gravel should be spread over the mortar and the whole batch turned over at least three times and until the gravel or stone is all incorporated into the batch and the consistency uniform throughout. Sufficient water should be added to make a wet mixture that will flow into place in the forms, and that can be puddled against forms with a shovel or tamping bar.

In depositing the concrete, first put down a 6-inch layer on the bottom of the excavation and puddle and tamp into place with a shovel or tamping bar. Next set up the forms on this base, keeping the spacing by using spacing blocks of wood cut 6 inches long, set between the forms. These blocks should be removed as soon as enough concrete is deposited in the bottom of the forms to hold them in place. The concrete should be well puddled and tamped against forms in order to insure a dense and water-tight wall.

The lid for the effluent tank can be cast in a mold of the required dimensions, and should have an iron ring embedded in the top while the concrete is green, to serve as a handle in lifting the cover.

In order to use the sanitary privy shown by accompanying cuts (figs. 6, 7, and 10) with this tank system, it is only necessary to line the space occupied by the can with zinc, cut a hole in the floor under the seat and immediately over the liquefying tank, and provide a float with rod. as shown by drawings. Materials required for one concrete liquefying and effluent tank, as shown by drawings:

Walls and floor 6 inches thick.

Two and a half barrels Portland cement.

Three-fourths yard of sand.

One and one-fourth yards clean gravel of a size to pass a 4-inch mesh screen and under.

One hundred and fifty feet -inch surfaced sheathing for forms.

One overflow pipe built up out of 2-inch galvanized-iron pipe and fittings, and with strainer and zinc lining for box under seat.

One piece -inch galvanized-iron pipe 12 inches long, to act as a guide for antisplasher rod. This pipe should be run through an augur hole in the forms before the concrete is poured and plumbed up to come level with privy floor. The antisplasher rod can be a or inch heart pine or hardwood rod let into augur hole in the antisplasher and fastened with a brad.

Oil or vinegar barrels (fig. 10) can be used for tanks if a cheaper and less permanent construction is desired. The barrels to be sunk below the surface of the ground or set on the surface and a platform and steps provided up to entrance. If set at the surface of the ground, additional materials will be required to board up around privy from the surface of the ground to floor line and for platform and steps, the quantity required depending on the height at which the tanks are set above the grade line.

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