Conversion from Fluid ounces per hour to Gallons per minute

Information about the Fluid ounce per hour (fl oz/h)

The fluid ounce per hour is a unit of volumetric flow rate equal to one imperial fluid ounce passing a point every hour. Its symbol is fl oz/h. An imperial fluid ounce is 28.413 millilitres, so an hour at this rate delivers about two tablespoons — a rate slow enough that it is measured by what has collected, not by what is moving.

Slow feeding and slow dosing account for most of its use. A drip feeder on a bird cage, a wick humidifier, a fragrance diffuser and a slow-release fertiliser injector on a greenhouse line all move liquid at a few fluid ounces per hour, and the reservoir capacity divided by that rate gives the interval between refills.

Domestic appliances are described by it in older British literature. A paraffin heater consumes a few fluid ounces per hour, a wick lamp rather less, and an oil-filled stove was once sold with its consumption stated exactly this way so that a household could calculate how long a gallon would last through a winter evening.

Evaporation and leakage measurements fall here too. Water lost from an open tank, brake fluid seeping past a seal, or condensate collected from a small cooling coil are all quantified per hour, because that is the shortest period over which enough accumulates to measure in an ordinary graduated cylinder.

The unit's usefulness lies in matching the observation to the human timescale. Nobody watches a drip for a second; a technician checks a container after an hour, a shift or a night, and expressing the rate per hour lets the observed volume be divided by the elapsed hours with no further arithmetic.

For orientation, 160 fluid ounces make an imperial gallon, so one fluid ounce per hour fills a gallon in a little under a week. Thirty-five fluid ounces per hour is about a litre per hour, and sixty fluid ounces per hour is one fluid ounce per minute.

One fluid ounce per hour equals about 28.41 millilitres per hour, about 0.02841 litres per hour, or about 0.01667 fluid ounces per minute.

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.