Cisterns
These may be made of galvanised iron or slate, when required to be movable or only of a moderate size. As permanent reservoirs for water, Cisterns are generally constructed with stone or brick, and coated inside with cement. The superior value of rain water over any other for plant cultivation and garden purposes generally, is unfortunately often overlooked when building glass houses, as it is frequently conducted to drains when accommodation for its reception should be provided in the shape of Cisterns. These can be placed above or below ground, either inside or adjoining the houses, and, in addition, should be provided with means of supply from another source when rain water fails. An overflow pipe should be attached, and, if practicable, arranged so as to unscrew and open a passage at the bottom, to allow of the Cistern being cleaned out. Iron Cisterns require galvanising in all cases, as this prevents the iron causing rust or otherwise affecting the water. Almost all sizes may be purchased ready for use, and are well adapted for placing in houses where permanent ones are not constructed, so that water may stand and become warmed before being applied to the plants. Cold water is very injurious to plants growing in a warm temperature; hence the necessity for Cisterns of some sort, placed near or over hot-water pipes if possible, and kept filled with water ready for use. Where hard water has, of necessity, to be used for pot plants outside in summer, it may be materially softened by being placed in large open Cisterns, and exposed for a time to the air. Cisterns may also be used successfully for cultivating, on a small scale, tropical or hardy water plants. In connection with a heating apparatus, the cold-water Cistern should, in all cases, be placed at least a few feet above the highest point of the pipes it has to supply. The size of Cistern for this purpose is immaterial, the important part being to keep it filled with water.