Page:Popular Science Monthly Volume 92.djvu/479

 Popular Science Monthly

��463

��FROM TANK.

��heavy loam soil is used, the discharge cham- ber must be larger and deeper, in order that the discharge interval may be lengthened and the distribution system be given ample time to aerate. If the distribution is in sandy or very porous soil the dis- charge may be more frequent.

The table of dimensions of septic tanks suggests sizes of settling and discharge chambers and the corresponding siphon sizes to apply to various average condi- tions. The depths of siphon chambers given are the minimum allowable.

The table is computed on the basis that the inlet and outlet of the settling cham- ber should be placed with their inverts 12 in. below the roof of the tank, thus making the depth of sewage in both settling and discharge chamber 12 in. less than the mean inside depth.

The tank dimensions given are for average cases only and are not standard for all such cases. They are sub- ject to variations to suit local conditions; yet care should be taken not to vary any of the essential dimensions, and not to go below the given minimum depth of the siphon chamber.

In the illustration Fig. 1, is shown a double-chamber septic tank for a family of six people. Another type of tank for a family of eight people is shown in Fig. 2. These tanks are suited to conditions where plenty of outlet fall is available. A double- chamber tank for a family of six persons is shown in Fig. 3. This tank is suited to flat ground where outlet fall is difficult to ob- tain, as will be noted by the difference in elevation between the floors of the two chambers. For satisfactory operation, a small septic tank should be a size suitable for use by at least six persons.

The septic tank, although airtight and supposedly watertight, should be located as far from the house and the well or spring as convenience and local surround- ings will permit, thus reducing the danger of pollution or nuisance in case of leakage or improper operation of the system.

���Fig. 6: Cross section of a single tile sew- age disposal system

��The sewer from the house should be of vitrified sewer pipe, usually 4 in. in size, with tightly cemented joints, and should

��GATE CHAMBER

���Fig. 5 : A ground plan for the laying of the tile in a system leading from a sewage dis- posal plant to drain the tanks underground

be laid to a grade of less than 9 in. per 100 ft. Where the fall from the house to the tank is excessive, it is a good plan to lay at least 100 ft. of tile to the mini- mum grade to break up entrance velocity. It is assumed that the farmer has a working knowledge of small concrete structures. The septic tank, prefer- ably of concrete, ^^v-m o o-v^oo-o^i'-v- should be made as ^/^/fe^^'^'og^^ nearly watertight /r/;:^'A\«8"VoV^^/<< as possible. The

��� �� ���walls should be 6 or

8 in, thick, the floor

4 to 6 in. thick, and

the roof about 6 in.

thick and reinforced.

Some means should

be provided at the

bottom to facilitate

the cleaning out of the settled sludge.

Either the floor may be sloped toward

��Fig. 7: A single tile system with underdrainage tile

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