Draft (water)

A suction pump creates a partial vacuum (a "draft") and the atmospheric pressure 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.

[1][2] Standard atmospheric pressure is 101 kPa (14.7 lbf/in2) and that can only raise water to a theoretical maximum of 10.3 metres (34 feet).

[3] Depending on application, fire department pumps lift water 6 to 10 metres (20 to 33 ft).

Multiple relays could be used if the need arises, with a suction pump drafting up to 10 metres (33 feet) and discharging at great distances.

It is also possible to use a gravity siphon 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.