Conversion from 2 Gallons per minute to Gallons per second

Information about the Gallon per minute (gal/min)

The gallon per minute is a unit of volumetric flow rate equal to one imperial gallon passing a point every minute. Its symbol is gal/min, usually abbreviated GPM. The imperial gallon is 4.54609 litres, so this unit sits comfortably in the range of pumps, wells and building services, which is where it did most of its work before metrication.

Water wells and boreholes are still described by it in Britain and Ireland. A domestic borehole yields 2 to 10 gallons per minute, an agricultural one 20 to 60, and a public supply borehole several hundred. The yield test that establishes the figure runs the pump for hours while watching the water level, and the sustainable yield in gallons per minute is what determines whether a licence can be granted.

Pumps and pumping stations were rated in it throughout the industrial era. Boiler feed pumps, sewage pumps and fire pumps all carried plates in gallons per minute, and older British pump curves plot head against this unit rather than against cubic metres per hour. Anyone matching a replacement pump to an old installation has to convert the duty point carefully.

Building services used it for hot and cold water services, heating circuits and cooling towers. A heating circuit's flow follows from the heat it must carry and the temperature drop across the circuit, and in imperial terms the arithmetic came out in gallons per minute against a drop in degrees Fahrenheit — a combination that survives in many older plant rooms.

The unit also has a firefighting history. British fire brigade pumps were classified as light, medium and heavy by their output in gallons per minute, and hydrant flow tests, hose reel ratings and sprinkler system design all rested on the same figure before European standards moved the trade to litres per minute.

For scale, one gallon per minute is about 4.5 litres per minute, and 13.2 gallons per minute is one litre per second. A domestic shower running at 9 litres per minute is just under 2 gallons per minute, which puts everyday plumbing at the low end of the unit's range.

One gallon per minute equals about 4.546 litres per minute, about 0.2728 cubic metres per hour, or about 1.201 US gallons per minute.

Information about the Gallon per second (gal/s)

The gallon per second is a unit of volumetric flow rate equal to one imperial gallon passing a point every second. Its symbol is gal/s. The imperial gallon is 4.54609 litres, defined in 1824 as the volume of ten pounds of water at a stated temperature, so one gallon per second moves about four and a half litres — and, conveniently, about ten pounds — every second.

Firefighting is the discipline that works at this scale. A hose reel delivers a fraction of a gallon per second, a standard hose line 1 to 2, and a major pumping appliance 10 or more. British fire service practice quoted pump capacities in gallons per minute for most of the twentieth century, and the per-second figure is what a hydraulic calculation of pressure loss in the hose actually uses.

Large pumps and water mains reach it easily. A borehole pump on a farm might deliver half a gallon per second, a district water main several tens, and a river intake for a power station hundreds. Since the gallon of water weighs ten pounds, a flow in gallons per second converts to a mass flow in stones per second by dividing by 1.4, an arithmetic that older British engineering handbooks used freely.

Flood and drainage engineering in Britain used the unit until metrication. Culvert capacities, pumping station ratings and land drainage schemes were designed in gallons per second or per minute, and much of the surviving infrastructure still carries plates giving its capacity in those terms, which anyone assessing an old asset must convert with care.

The imperial gallon must be distinguished from the American one, which is 3.78541 litres — about twenty per cent smaller. A pump rated 10 gallons per second delivers 45.5 litres per second in Britain and 37.9 in the United States, a difference far too large to ignore in any calculation of capacity or of cost.

For scale, one gallon per second fills a domestic bath in about twenty-five seconds, and 0.22 gallons per second is one litre per second. A flow of ten gallons per second is a small stream, running at about 45 litres per second.

One gallon per second equals about 4.546 litres per second, about 0.004546 cubic metres per second, or about 1.201 US gallons per second.