It is of the utmost importance to the health of the inmates that the cellar be kept as free from dampness as possible.

In the case of damp soil, a system of subsoil drainage should always be employed.

Subsoil drains are constructed of earthenware drain tile, laid with open, uncemented joints. The moisture of the damp soil enters the drain through these open joints. The subsoil drain should be laid completely around the cellar wall, and whenever necessary may have branches running in to the center of the cellar. The drain should be laid on a level with the bottom of the foundation wall, and about six inches inside of it. The subsoil drain should be laid on an even grade, pitching toward the catch basin to which it is to be connected, it being necessary to connect it always into such a catch basin properly trapped and entered into the house drain.

The catch basin is generally constructed of concrete, and made in the form of an open well in the concrete cellar bottom, and covered by a stone or cast-iron cover.

Whenever the sewer to which such a catch basin is connected is known to back up, the trap of the catch basin should be provided with a back-water valve.