CISTERN.
The cistern is generally located near the rear kitchen wall, say ten or twelve feet therefrom. The walls, arch, and neck are usually four inches in thickness when capacity of cistern does not exceed one hundred and twenty-five barrels. Otherwise the brick work mentioned should be eight inches in thickness. The brick should be laid in domestic cement, and smoothly coated with Portland cement. It should be connected with the down spouts of the house by means of vitrified drain-pipe, the same as described in connection with plumbing work, though it has no connection therewith.
The following table gives capacity of cisterns of various sizes.
CAPACITY OF CISTERN IN GALLONS FOR EACH TEN INCHES IN DEPTH.
| DIAM. IN FEET | GALLONS. | DIAM. IN FEET | GALLONS. | DIAM. IN FEET | GALLONS. |
| 2 | 19·50 | 6½ | 206·85 | 12 | 705·0 |
| 2½ | 30·50 | 7 | 239·88 | 13 | 827·4 |
| 3 | 44·60 | 7½ | 275·40 | 14 | 959·6 |
| 3½ | 59·97 | 8 | 313·33 | 15 | 1,101·6 |
| 4 | 78·33 | 8½ | 353·72 | 20 | 1,958·4 |
| 4½ | 99·14 | 9 | 396·56 | 25 | 3,059·9 |
| 5 | 122·40 | 9½ | 461·40 | 30 | 4,406·4 |
| 5½ | 148·10 | 10 | 489·60 | 35 | 5,990·0 |
| 6 | 176·25 | 11 | 592·40 | 40 | 7,831·0 |
FILTERS.
There are various ways of forming a filter. One is to have a small cistern of eight or ten barrel capacity, located between the main cistern and house. It should be divided by a brick wall laid in mortar, but not cemented on either side. The water enters on one side, passes through the brick wall in the middle, and from thence to the cistern beyond. Another plan is to cement the wall, leave an opening at the bottom, and pack the side on which the water enters with charcoal, sand, and gravel. The water passes through this packing and the opening below to the other side of the filter, and then to the cistern. Still another plan is to build the partition as first described on the inside of the cistern proper. All of the water passes to one side of the divided cistern, and through the partition before being drawn out. Thus it has to pass through the brick before it is to be drawn out. Still another filter is made by building what is called a beehive in the bottom of the cistern. It is a beehive form of brick work, with the pump pipe leading to the inside, so that all water has to be drawn through the brick beehive before it is pumped out. According to this plan, as well as the others mentioned, the water is strained through the brick.
It is best that the cistern and independent filter, when used, should be provided with iron rims and cast-iron covers. It is good practice to connect the cistern with a dry well, which is constructed the same as an open vault excepting that the top is arched. This dry-well connection is by means of five-inch vitrified pipe laid in the same manner as sewer pipe.
There is a practice, altogether too common among builders, of connecting the cistern overflow with the vault or sewer. Nothing could be worse than this. The water is certain to be polluted.