[Illustration: Fig. 20.--Sewer-cleaning tools--how to use them. _A_, Ordinary 1½ or 2 inch auger welded to a piece 1¾-inch extra strong wrought pipe about 5 feet long: the stem is lengthened by adding other pieces of pipe with screw couplings, and is fitted with a pipe handle; all cleaning work should proceed upstream; _B_, twist or open earth auger; _C_, ribbon or closed earth auger; _D_, spiral or coal auger; _E_, ship auger; _F_, root cutter; _G_, sewer rods, with hook coupling, usually of hickory or ash 1 or 1¼ inches in diameter and 3 or 4 feet long; _H_, gouge for cutting obstructions; _I_, scoop for removing sand or similar material; _J_, claw, and _K_, screw, for removing paper and rags; _L_, scraper; _M_, wire brush for removing grease, drawn back and forth with a wire or rope; _N_, homemade wire brush (for a 5-inch sewer use a 1½-inch wooden pole to which is securely tacked a piece of heavy rubber, canvas, or leather belting or harness leather 5½ by 8 inches, spirally studded, as shown, with ordinary wire nails 1½ inches in length)] In Northern States, particularly in exposed situations, it is desirable to have the top of the tank 1 to 2 feet underground, thus promoting warmth and uniformity of temperature in the sewage. In Southern States this feature is less important, and the top of the tank may be flush with the ground. Every tank should be tightly covered, for the reasons above stated and to guard against the spread of odors, the transmission of disease germs by flies, and accidents to children. Considerable latitude is allowable in the design and construction of septic tanks. No particular shape or exact dimensions can be presented for a given number of people. One family of 5 persons may use as much water as another family of 10 persons; hence the quantity of sewage rather than the number of persons is the better basis of design. Exact dimensions are not requisite, for settlement and septicization proceed whether the sewage is held a few hours more or a few hours less. As to materials of construction, some form of masonry, either brick, building tile, rubble, concrete, or cement block, is employed generally. Vitrified pipe, steel, and wood have been used occasionally. [Illustration: Fig. 21.--One-chamber septic tank--does nothing more than a tight cesspool. Brick construction, heavily plastered inside; size suitable for 180 to 280 gallons of sewage daily (nominally 4 to 7 persons)]