| US Gallons per hour (gal US/h) | Liters per minute (L/min) |
|---|---|
| 1 US Gallon per hour | 0.0630901964 L/min |
| 2 US Gallons per hour | 0.1261803928 L/min |
| 3 US Gallons per hour | 0.1892705892 L/min |
| 4 US Gallons per hour | 0.2523607856 L/min |
| 5 US Gallons per hour | 0.315450982 L/min |
| 10 US Gallons per hour | 0.630901964 L/min |
| 20 US Gallons per hour | 1.261803928 L/min |
| 25 US Gallons per hour | 1.57725491 L/min |
| 50 US Gallons per hour | 3.15450982 L/min |
| 100 US Gallons per hour | 6.30901964 L/min |
| Reference | US Gallons per hour (gal US/h) | Liters per minute (L/min) |
|---|---|---|
| A domestic shower | 142.653 gal US/h | 9 L/min |
| A kitchen tap | 158.503 gal US/h | 10 L/min |
| A garden hose | 237.755 gal US/h | 15 L/min |
| The Amazon river | 1.98763 × 1011 gal US/h | 1.254 × 1010 L/min |
The US gallon per hour is a unit of volumetric flow rate equal to one United States gallon passing a point every hour. Its symbol is gal US/h, commonly abbreviated GPH. At 3.785 litres to the gallon, an hour at this rate delivers a little under four litres, which places it among the slow, continuous flows of heating, irrigation and fuel systems.
Drip irrigation is its most familiar use in America. Emitters are sold rated at 0.5, 1 and 2 gallons per hour, and a garden bed is designed by choosing an emitter for each plant and multiplying by the number of plants. A zone of two hundred one-gallon emitters draws 200 gallons per hour, and a two-hour cycle applies 400 gallons — figures a homeowner can check against the water bill.
Oil burners are rated in it in the United States, exactly as in Britain. A residential oil furnace carries a nozzle marked 0.75 or 1.00 gallons per hour, and multiplying by about 140,000 British thermal units per gallon gives the burner's firing rate. The nozzle is thus both a fuel metering device and the effective rating plate of the appliance.
Water heaters and small appliances follow. A tankless water heater's recovery, an ice machine's water consumption, a humidifier's evaporation rate and a coffee urn's draw are all commonly expressed in gallons per hour, since these appliances run more or less continuously and are chosen to match a daily demand.
Fuel consumption of engines under steady load is quoted this way in American practice. A generator burns 0.5 to 3 gallons per hour depending on size and load, a boat's engine several, and a large marine diesel dozens. Dividing the tank capacity by the hourly rate gives the endurance, which for a boat is the number that actually matters.
For scale, one US gallon per hour is about 3.79 litres per hour, and 264 gallons per hour is about a cubic metre per hour. Sixty gallons per hour is one gallon per minute, so the two American flow units are connected by the same factor that connects the minute to the hour.
One US gallon per hour equals about 3.785 litres per hour, about 0.003785 cubic metres per hour, or about 0.8327 imperial gallons per hour.
The litre per minute is a unit of volumetric flow rate equal to one litre passing a point every minute. Its symbol is L/min. It is the unit of taps, showers and small pumps — the flows a person meets directly, at a rate slow enough that a minute is the natural interval to count over.
Household plumbing is specified in it almost everywhere. A modern shower head delivers 6 to 9 litres per minute, an older one 15 or more, a kitchen tap 5 to 10, and a bath filler 15 to 20. Water-efficiency regulations in many countries set maximum figures in exactly these terms, because the flow rate multiplied by a typical shower length gives the volume of water and the energy needed to heat it.
That calculation is the reason the unit matters beyond plumbing. Reducing a shower from 12 to 8 litres per minute cuts both the water and the heating energy by a third, and heating water is one of the largest energy uses in a house. A restrictor costing very little changes a household's energy bill measurably.
Medicine uses the unit for gases. Oxygen therapy is prescribed in litres per minute — 2 through a nasal cannula for mild supplementation, 15 through a mask with a reservoir in an emergency — and the flowmeter on the wall of a hospital room is calibrated in exactly this unit. Anaesthetic machines are set the same way.
Engines and compressors also appear here. A small air compressor delivers 100 to 200 litres per minute of free air; a car's cooling system circulates tens of litres per minute; a garden pump moves 20 to 60. In each case the number is the useful one because the equipment runs for minutes at a time rather than seconds.
Sixty litres per minute is one litre per second, so the two units differ by the same factor as the two time units. That makes the conversion easy to do mentally, and it explains why the same equipment is often described in litres per minute by its manufacturer and litres per second by the engineer designing the system it goes into.
One litre per minute equals about 0.01667 litres per second, 1,000 millilitres per minute, or about 0.22 imperial gallons per minute.