=Flush Tanks.=--The water closet depends for its action on one of two general types of flush tanks, the high and the low forms. The tank is automatically filled with water and when wanted, a large volume of water is suddenly discharged into the sewer, carrying with it the contents of the seat. The tank again fills and is ready for use when required. As illustrations of high flush tanks, those shown in Figs. 105 and 106 furnish examples of a simple and efficient form. The details of the mechanism of this type of tank are shown in Fig. 107. The pipe from the water supply is attached at _G_ to the automatic valve _F_, which keeps the tank filled with water. The piece _F_ of the valve is held against the opening by the pressure exerted through the float _E_. The float is a hollow copper ball. As the ball is lifted it exerts a pressure in proportion to the amount it is submerged. When the water reaches the level _A-A_, the valve is tightly closed. As the water is discharged from the tank the ball follows the level of the water and opens the valve, allowing the water to enter and again fill the tank. [Illustration: FIG. 107.--Details of construction of a simple type of siphon flush tank.] The siphon is made of cast iron, and in the figure is shown cut through the center. The lower end fits loosely in the piece _K_, and makes a water-tight joint around its outer edge, by resting on a rubber ring _C-C_. The right-hand side of the siphon is open at _H_, and when the tank is full, the level of the water is at _A-A_, which is almost at the top of the division plate. To discharge the tank, the chain _L_, attached to the lever _B_, is pulled down; this action raises the siphon from its seat. As soon as the siphon is lifted, the water rushes through the opening around _C-C_, into the pipe _K_; this causes a partial vacuum to form in _D_, and the water is lifted over the division plate _K_, and flows out at _D_, forming the siphon. As soon as the siphonic action begins the siphon may be dropped back on the seat and the water will continue to discharge until the tank is empty. =Low-down Flush Tank.=--The low-down flush tank for water closets has met with so much favor that it has to a great extent displaced the high tank. The reason for this is because of its advantages over the other style. The low tank is more accessible, more easily kept clean, and better adapted to low ceilings. It is used successfully as a siphon tank, but other forms are in use with satisfactory results.