Pumps and Water Filters

136. Suction Pumps. A pump is a device for lifting water. The pumps in common use work on the principle that water which is under the pressure of air will rise to fill a vacuum or a partial vacuum. The pump is composed of a combination of valves and a piston for forcing the air out of the pipe to allow the water from below to be forced into it. A valve catches the water as it starts to flow back. The weight of the water holds the valve closed.

An outlet above the piston permits the water to flow into a tank or sink when the piston is again lifted to make a new vacuum and draw more water (Fig. 68).

137. Care of Pumps. The leather or material forming the piston must be kept moist, or it will shrink and leak. When it becomes worn and old, it must be renewed. It is not a difficult task to put new packing on a small suction pump. To do this, remove the pin attaching the piston to the handle. Lift out the piston, unscrew the bolt which holds the leather packing in place; put on the new packing, and replace the bolt, piston and pin.

Always pump with a regular, even stroke—a jerky one tends to wear the working parts of the pump.

The cylinder and pipe containing water must not be allowed to freeze. There is usually a plug in the pipe which may be removed to let out the water when there is danger of freezing. A cracked cylinder or pipe will leak air and not raise water.

Keep the bearings for the handle well oiled. When the pump gets old, the cylinder becomes worn and leaks. It can sometimes be replaced with a new cylinder, or more packing must be put on the piston.

138. Force Pumps. Force pumps are used on deep wells and in forcing water into storage tanks. They should be kept oiled; they should be operated with an even stroke, and the packing in them should be renewed if they leak air. In force pumps, the valves differ in their arrangement from suction pumps (Fig. 69).

139. Compressed-Air Pumps. Compressed-air pumps consist of a tank for storing the compressed air—a pump to force air into the tank and cylinders equipped with valves. These act automatically. Whenever an outlet pipe is opened, the extra pressure of air from the storage tank raises the water from the well or cistern (Fig. 70). Air should be kept in the pressure tank.

When this arrangement is used, open and close faucets slowly, not with a jerk. Fig. 70-a shows plumbing where such a system is used.

140. Water Filters. Water filters are devices for straining minute particles out of water. They are made of sand, charcoal or porcelain, kisselguhr and other materials. They are without value unless they are kept clean. A dirty filter is worse than none. Almost the only way to clean them is to sterilize them or put new material in them. Only with expert care can filters be made effective for removing disease germs. A dirty filter may prove a menace. Filters are valuable for removing coarse dirt from the water.

Filters on faucets should be cleaned or renewed every day. Large filters for rain water should be renewed every few months.