Filters on faucets should be cleaned or renewed every day. Large filters for rain water should be renewed every few months.
CHAPTER XX
Pressure Tanks; Plumbing Fixtures
141. Pressure Tanks. A pressure tank is a device for storing water under pressure. It is usually placed in the basement of dwelling houses.
142. Construction of the Pressure Tank. The tank is tight and strong, so that it will hold air and water under pressure. The tank originally has some air in it. When the water is pumped in, the air not being able to escape, is compressed. When there is a chance for water to escape from the tank which is connected to water pipes, the pressure of the compressed air on the water forces it to upstairs rooms and other points. To this tank is attached a pressure gage which indicates the amount of pressure; or, in other words, the amount of water in the tank, for when the water gets low, the pressure is reduced unless the air has escaped. A glass gage shows the height of water. Provision is made to let some air into the tank, for otherwise it may in time be all forced out of the tank or absorbed by the water. The water in a pressure tank may be used to pump water from a cistern into another tank.
143. Care of Pressure Tanks. A pressure tank must not be pumped up to the extent that the pressure becomes greater than the strength of the tank. A safety valve is used in controlling the pressure.
144. Hot-Water Kitchen Tank. A force pump is generally used for pumping water into kitchen tanks, except when water from another tank, such as a city reservoir, flows into it.
