Typically the fill valve is secured by a ballcock shank washer, which prevents leakage from the supply line. Although this does not stop the wastage of water, it avoids the flooding that would otherwise occur after a single-point valve failure. Should the float or valve fail and allow the water level to exceed the fill line, the water will pour into the overflow tube and out to the bowl (in the flapper valve type) or to an outside drain (in the siphon type). Toward the end of the discharge process, the ballcock responds to the drop in water level and refills the tank. When the column of water passes over the siphon bend and starts to fall down the exit pipe, the siphon action continues to empty the tank until the water in the tank falls below the siphon intake. The rod or chain lifts a piston that pulls an initial charge of water up into the siphon. Īnother discharge mechanism, common in the United Kingdom, is a siphon (or syphon). Note: These diagrams represent a configuration typical in the USA, mechanisms may vary in other countries. The flapper has closed, and the tank refills within seconds.ġ. The handle is pressed and the flush cycle begins. Once the flapper valve closes, the water flow from the fill valve continues until the tank level again reaches the fill line. Water is fed to the tank to replenish its supply, and a smaller flow is directed into the overflow tube to refill the bowl. As the tank water level drops, the float descends and actuates the fill valve. The mechanism may be a flapper valve, which is designed to sink more slowly than the water, which will exit to the toilet bowl below, so that the tank may empty. When the handle of a flush toilet with a tank is turned, a discharge mechanism is activated by means of a rod or chain. This is an example of negative feedback and of proportional control. When the water level rises, the float rises with it once it rises to a pre-set level, the mechanism forces the lever to close the valve and shut off the water flow. The valve is connected to the incoming water supply, and is opened and closed by the lever which has the float mounted on the end. The float is often ball-shaped, hence the name ballcock. It consists of a valve connected to a hollow, sealed float by means of a lever mounted near the top of the tank. The ballcock device was patented in 1797 for use in steam engines by Edmund Cartwright. The modern ballcock was invented by José Antonio de Alzate y Ramírez, a Mexican priest and scientist, who described the device in 1790 in the Gaceta de Literatura Méxicana. ( Learn how and when to remove this template message)Ī ballcock (also balltap or float valve) is a mechanism or machine for filling water tanks, such as those found in flush toilets, while avoiding overflow and (in the event of low water pressure) backflow. JSTOR ( June 2013) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
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