A privy when safely located and properly built and maintained is satisfactory for its purpose on the farm. Privies should be built 50 to 150 feet from the farmhouse, preferably on the opposite side of the house from prevailing winds, and at least 50 feet from the well. A site downhill from the well is generally safest. In some cases, however, the ground water may flow in a direction opposite to the slope of the surface, in which case the privy should be built on the other side of the well. Direction of flow may sometimes be learned from soil surveys, well-driller's data, or other similar sources. A distance of at least 6 feet from fences or other buildings allows for proper mounding of the privy and keeps it away from roof drainage from adjacent buildings.

Good, tight construction with screened ventilators keeps insects and birds from entering, prevents rapid deterioration of the building, and provides greater comfort for the user.

Certain features, while not essential to sanitation and satisfactory service, add to personal convenience. A paved walkway, well protected from cold winds and rain, is desirable. A neat, whitewashed lattice, as shown in figure 13, an arbor covered with vines, or a hedge screen adds to privacy.

The earth-pit privy is the simplest to build and the one most widely used. It is not generally recommended in localities where underground rock has crevices.

For a sanitary type of privy with reinforced concrete[9] floor, riser, and supporting sills see figure 14. Because privy units are commonly used as urinals, the use of impervious materials for risers and floors facilitates cleanliness. In the colder climates, wood treated with a preservative is durable and reduces the problem of moisture condensation. Therefore, wood could be used if approved by the State department of health.

When it is considered impracticable to build the slab and riser of concrete, these parts may be of wood, as shown in figure 16. The building itself may be as shown in either illustration. A wood structure is easy to move to a new location.

A pit with a minimum capacity of 50 cubic feet[10] will usually serve five people over a period of 5 to 10 years. The privy should be moved when the pit is filled to within 18 or 20 inches of the top and a strong disinfectant spread in the old pit before covering it with earth.

It is important to have the earth-pit privy more than 50 feet from the well even where the water table is not near the surface. The ground water should flow from the well toward the privy, and it is important that this direction of flow be determined in advance.

Wood is most commonly employed for the main part of the building. The ground outside should be sloped as shown, to shed water away from the building, and the roof should extend beyond the walls to shed water away from the pit.

CARE AND MAINTENANCE

All privies require periodic attention. Seats and covers should be washed weekly with soap and water or with disinfectants, such as cresol, pine oil, and hypochlorite or chloride of lime. These have deodorant properties and are available at most grocery or drug stores. Druggists generally carry a more refined product and consequently the price is higher.

During the fly season fly and mosquito eggs will be destroyed by pouring half a pint of crude oil, crankcase oil, fuel oil, kerosene, or borax solution (1 pound powdered borax dissolved in about 10 gallons of water) over the contents of the pit about once a week.

Odors from privy pits and vaults can be reduced by covering the contents with dry earth, ashes, manure, or sawdust. These materials fill up the pit rather quickly, but can be used where other deodorants are not available. Sometimes two cakes of yeast dissolved in 2 gallons of water are effective in reducing odors. Commercial deodorants are available from suppliers of disinfectants.

If a person in the family has typhoid fever or is a carrier of that disease or has dysentery, it is advisable to disinfect the excreta. Fire, live steam, boiling water, and such chemicals as caustic soda (sodium hydroxide), caustic potash (potassium hydroxide), or hypochlorite or chloride of lime may be used. The heat generated by the slacking of quicklime is also effective. Best results are obtained if the infected material is treated prior to depositing it in the privy. Further advice may be obtained from physicians, local health officers, or State health departments.