Ballcock
Encyclopedia
A ballcock is a mechanism
or machine for filling water tanks, such as those found in flush toilet
s, while avoiding overflow and (in the event of low water pressure) backflow. The modern ballcock was invented by Joseph Bramah and Thomas Twyford..
The diagrams and description ONLY apply to the USA (these are not typical in the UK or Europe). It consists of a valve
connected to a hollow sealed float
(literally, a device that floats on top of water) by means of a lever
, mounted near the top of the tank. 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. When the water level rises, the float rises with it; when the level rises to a pre-set level (called a fill line), the mechanism forces the lever to close the valve and shut off the water flow. This is an example of negative feedback
and of proportional control
.
When a toilet's handle is turned, a flapper valve is pulled upward by means of a rod or chain. It is designed to sink more slowly than the water, which will exit to the toilet bowl below, so that the tank may empty. As the tank water level drops, the float descends and actuates the fill valve. Water is fed to the tank to replenish its supply, and a smaller flow is directed into the overflow tube to refill the bowl.
Once the flapper valve closes, the water flow from the fill valve continues until the tank level again reaches the fill line. 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. (Note that although this wastes water, it is a successful attempt to mitigate the flooding that would otherwise occur under that single-point valve failure.)
These devices are sold at most hardware
, plumbing
supply, and home improvement stores.
Mechanism (engineering)
A mechanism is a device designed to transform input forces and movement into a desired set of output forces and movement. Mechanisms generally consist of moving components such as gears and gear trains, belt and chain drives, cam and follower mechanisms, and linkages as well as friction devices...
or machine for filling water tanks, such as those found in flush toilet
Flush toilet
A flush toilet is a toilet that disposes of human waste by using water to flush it through a drainpipe to another location. Flushing mechanisms are found more often on western toilets , but many squat toilets also are made for automated flushing...
s, while avoiding overflow and (in the event of low water pressure) backflow. The modern ballcock was invented by Joseph Bramah and Thomas Twyford..
The diagrams and description ONLY apply to the USA (these are not typical in the UK or Europe). It consists of a valve
Valve
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...
connected to a hollow sealed float
Float (liquid level)
Liquid level floats, also known as float balls, are spherical, cylindrical, oblong or similarly-shaped objects, made from either rigid or flexible material, that are buoyant in water and other liquids. They are non-electrical hardware frequently used as visual sight-indicators for surface...
(literally, a device that floats on top of water) by means of a lever
Lever
In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to either multiply the mechanical force that can be applied to another object or resistance force , or multiply the distance and speed at which the opposite end of the rigid object travels.This leverage...
, mounted near the top of the tank. The valve is connected to the incoming water supply
Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...
, and is opened and closed by the lever which has the float mounted on the end. When the water level rises, the float rises with it; when the level rises to a pre-set level (called a fill line), the mechanism forces the lever to close the valve and shut off the water flow. This is an example of negative feedback
Negative feedback
Negative feedback occurs when the output of a system acts to oppose changes to the input of the system, with the result that the changes are attenuated. If the overall feedback of the system is negative, then the system will tend to be stable.- Overview :...
and of proportional control
Proportional control
A proportional control system is a type of linear feedback control system. Two classic mechanical examples are the toilet bowl float proportioning valve and the fly-ball governor....
.
When a toilet's handle is turned, a flapper valve is pulled upward by means of a rod or chain. It is designed to sink more slowly than the water, which will exit to the toilet bowl below, so that the tank may empty. As the tank water level drops, the float descends and actuates the fill valve. Water is fed to the tank to replenish its supply, and a smaller flow is directed into the overflow tube to refill the bowl.
Once the flapper valve closes, the water flow from the fill valve continues until the tank level again reaches the fill line. 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. (Note that although this wastes water, it is a successful attempt to mitigate the flooding that would otherwise occur under that single-point valve failure.)
These devices are sold at most hardware
Hardware
Hardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....
, plumbing
Plumbing
Plumbing is the system of pipes and drains installed in a building for the distribution of potable drinking water and the removal of waterborne wastes, and the skilled trade of working with pipes, tubing and plumbing fixtures in such systems. A plumber is someone who installs or repairs piping...
supply, and home improvement stores.
| A traditional gravity toilet tank | ||
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| The handle is pressed and the flush cycle begins. | The flapper has closed, and the tank refills within seconds. | |
| 1. float, 2. fill valve, 3. lift arm, 4. tank fill tube, 5. bowl fill tube, 6. flush valve flapper, 7. overflow tube, 8. flush handle, 9. chain, 10. fill line, 11. fill valve shaft, 12. flush tube |
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