The well-known forms of steam-pumping engines need not be considered in detail, because high-pressure steam is not often available in country houses. Where electric current is brought to the building, or generated for lighting purposes, water may be pumped by an electric pump. Electric motors are easy and convenient to run, very clean, but so far not very economical. Electric pumps may be arranged so as to start and stop entirely automatically. Water may be pumped, where electricity forms the power, either by triplex plunger pumps or by rotary, screw, or centrifugal pumps.
Space forbids giving a description of the many simpler devices used for lifting water. In small farmhouses lift and force pumps worked by hand are now introduced, and the old-fashioned, moss-covered draw-bucket, which is neither convenient nor sanitary, is becoming a relic of past times.
The water pumped is stored either in small masonry or earth reservoirs, or else in storage tanks of either wood, iron, or steel, placed on a wood or steel tower. Wooden tanks are cheap but unsightly, require frequent renewal of the paint, and give trouble by leaking, freezing, and corrosion of hoops. In recent years elevated tanks are supplanted by pressure tanks. Several such systems, differing but little from one another, are becoming quite well known. In these water is stored under suitable pressure in air-tight tanks, filled partly with water and partly with air.
One system consists of a circular, wrought-steel, closed tank, made air- and water-tight, a force pump for pumping water into the tank, and pipe connections. The tank is placed either horizontally or vertically in the basement or cellar, or else placed outdoors in the ground at a depth below freezing. Water is pumped into the bottom of the tank, whereby its air acquires sufficient pressure to force water to the upper floors.
This simple system has some marked advantages over the outside or the attic tank. In these, water gets warm in summer and freezes in winter. Vermin and dust get into the tank, and the water stagnates. In the pressure tank, water is kept aërated, cool, and clean.
Another pressure tank has an automatic valve, controlled by a float and connected with suction of pump. It prevents the tank from becoming water-logged by maintaining the correct amount of air inside.