Tap (valve) - Water Taps

Water Taps

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. In kitchens and bathrooms mixer taps are commonly used. In this case, hot and cold water from the two valves is mixed before reaching the outlet, allowing the water to emerge at any temperature between that of the hot and cold water supplies. Mixer taps were invented by Thomas Campbell of Saint John, New Brunswick and patented in 1880.

For baths and showers, mixer taps frequently incorporate some sort of pressure balancing feature so that the hot/cold mixture ratio will not be affected by transient changes in the pressure of one or the other of the supplies. This helps avoid scalding or uncomfortable chilling as other water loads occur (such as the flushing of a toilet). Rather than two separate valves, mixer taps frequently use a single, more complex, valve controlled by a single handle (single handle mixer). The handle moves up and down to control the amount of water flow and from side to side to control the temperature of the water. Especially for baths and showers, the latest designs do this using a built-in thermostat. These are known as thermostatic mixing valves, or TMVs, and can be mechanical or electronic. There are also faucets with color LEDs to show the temperature of the water.

If separate taps are fitted, it may not be immediately clear which tap is hot and which is cold. The hot tap generally has a red indicator while the cold tap generally has a blue or green indicator. In the United States, the taps are frequently also labeled with an "H" or "C". Note that in countries with Romance languages, the letters "C" for hot and "F" for cold are used (from French "chaud"/Italian "caldo" (hot) and French "froid"/Italian "freddo" (cold)). This can create confusion when English speakers visit these countries or vice versa. Mixer taps may have a red-blue stripe or arrows indicating which side will give hot and which cold.

In most countries, there is a standard arrangement of hot/cold taps. For example, in the United States and many other countries, the hot tap is on the left by building code requirements. Many installations exist where this standard has been ignored (called "crossed connections" by plumbers). Mis-assembly of some single-valve mixer taps will exchange hot and cold even if the fixture has been plumbed correctly.

Most handles on residential homes are connected to the valve shaft and fastened down with a screw. Although on most commercial and industrial applications they are fitted with a removable key called a "loose key", "water key", or "sillcock key", which has a square peg and a square ended key to turn off and on the water. You can also take off the "loose key" to prevent vandals from turning on the water. In older buildings before the "loose key" was invented it was common for some landlords or caretakers to take off the handle of a residential tap, which had teeth that would meet up with the gears on the valve shaft. This Teeth and cog system is still used on most modern faucets. Although most of the time a "loose key" is on industrial and commercial applications sometimes you may see a "loose key" on homes by the seashore to prevent passers-by from washing the sand off their feet.