Tap (valve)

Water for baths, sinks and basins can be provided by separate hot and cold taps; this arrangement is common in older installations, particularly in public washrooms/lavatories and utility rooms/laundries.

This helps avoid scalding or uncomfortable chilling as other water loads occur (such as the flushing of a toilet).

Mixer taps may have a red-blue stripe or arrows indicating which side will give hot and which cold.

Mis-assembly of some single-valve mixer taps will exchange hot and cold even if the fixture has been plumbed correctly.

[citation needed] Before the "loose key" was invented it was common for some landlords or caretakers to take off the handle of a tap, which had teeth that would meet up with the gears on the valve shaft.

The term tap is widely used to describe the valve used to dispense draft beer from a keg, whether gravity feed or pressurized.

Like all ball valves its handle will parallel the gas line when open and be perpendicular when closed, making for easy visual identification of its status.

Bubbles of cool water vapor form and collapse at the restriction, causing the familiar hissing sound.

Most older taps use a soft rubber or neoprene washer which is screwed down onto a valve seat in order to stop the flow.

This is called a "globe valve" in engineering and, while it gives a leak-proof seal and good fine adjustment of flow, both the rubber washer and the valve seat are subject to wear (and for the seat, also corrosion) over time, so that eventually no tight seal is formed in the closed position, resulting in a leaking tap.

Gate valves use a metal wedge with a circular face, usually the same diameter as the pipe, which is screwed into place perpendicularly to the flow, cutting it off.

Thermostatically controlled electronic dual-purpose mixing or diverting valves are used within industrial applications to automatically provide liquids as required.

Foot controlled valves are installed within laboratory and healthcare/hospitals, as well as in industrial settings where extremely dirty hands operating taps might leave residues on them.

Modern taps often have aerators at the tip to limit water flow and introduce air in the form of bubbles to reduce splashing.

These taps exploit the uniquely low value of the coefficient of friction of 2 ceramic surfaces in contact, especially in the presence of water as a lubricant.