The term drafting water refers to the use of suction to move a liquid such as water from a vessel or body of water below the intake of a suction

Suction

Suction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not...

 pump

Pump

A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...

. A rural fire department

Volunteer fire department

See also the Firefighter article and its respective sections regarding VFDs in other countries.A volunteer fire department is a fire department composed of volunteers who perform fire suppression and other related emergency services for a local jurisdiction.The first organized force of...

 or farmer might draft water from a pond as the first step in moving the water elsewhere. A suction pump creates a partial vacuum (a "draft") and the atmospheric pressure

Atmospheric pressure

Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...

 on the water's surface forces the water into the pump, usually via a rigid pipe (sometimes called a "dry hydrant") or a semi-rigid "hard suction hose

Hard suction hose

Hard suction hose is a specific type of fire hose used in drafting operations, when a fire engine uses a vacuum to draw water from a portable water tank, pool, or other static water source. It is built to withstand vacuum, rather than pressure, abrasion, and heat...

".

Standard atmospheric pressure is 101 kPa (14.7 lbf/in²) and that can only raise water to a theoretical maximum of 10.3 metres (33.9 ft). Depending on application, fire department pumps lift water 6 to 10 metres (20 to 30 ft).

To reduce drafting friction and obtain a larger flow or higher lift, a larger cross-section of suction hose is employed. For example, using a 5 inch (127 mm) hose, a pump that could lift 500 US gallons per minute (30 L/s) up 23 feet (7 m) would only be able to lift the same amount of water 12.5 feet (4 m) through a 3.5 inch (76 mm) hose. Fire engines are often seen carrying two or three 10 foot (3 m) lengths of suction hose, but the longer the lift, the lower the flow, for a fixed diameter suction hose and a given pump. Multiple relays could be used if the need arises, with a suction pump drafting up to 10 metres (30 ft), and discharging at great distances.

It is also possible to use a gravity siphon

Siphon

The word siphon is sometimes used to refer to a wide variety of devices that involve the flow of liquids through tubes. But in the English language today, the word siphon usually refers to a tube in an inverted U shape which causes a liquid to flow uphill, above the surface of the reservoir,...

 to draft water for a small lift, and this technique is often used in forest fire suppression, where portable reservoirs of 1,000 to 3,000 US gallons (5 to 10 m³) are filled with water and small hoses are used downhill of the tanks. The nozzle pressure is proportional to its distance below the reservoir surface. Forty-three percent of the distance, in feet, is approximately the number of pounds per square inch pressure (e.g., 100 feet lower: 43 psi). The tank may itself be gravity-fed through hoses from a nearby water source, or by pumps or helicopters delivering water from further away.

See also

• Glossary of firefighting terms
  Glossary of firefighting terms
  Firefighting jargon includes a diverse lexicon of both common and idiosyncratic terms. One problem that exists in trying to create a list such as this is that much of the terminology used by a particular department is specifically defined in their particular standing operating procedures, such that...
  
  
• Portable water tank
  Portable water tank
  A portable water tank is a collapsible temporary tank designed for the reserve storage of water in firefighting, emergency relief, and military applications. These tanks can be either supported or unsupported. The supported tanks have a steel or aluminum frame and range in size from 600 to 5000 US...