| US Gallons per hour (gal US/h) | Cubic centimeters per second (cm³/s) |
|---|---|
| 1 US Gallon per hour | 1.05150327333 cm³/s |
| 2 US Gallons per hour | 2.10300654667 cm³/s |
| 3 US Gallons per hour | 3.15450982 cm³/s |
| 4 US Gallons per hour | 4.20601309333 cm³/s |
| 5 US Gallons per hour | 5.25751636667 cm³/s |
| 10 US Gallons per hour | 10.5150327333 cm³/s |
| 20 US Gallons per hour | 21.0300654667 cm³/s |
| 25 US Gallons per hour | 26.2875818333 cm³/s |
| 50 US Gallons per hour | 52.5751636667 cm³/s |
| 100 US Gallons per hour | 105.150327333 cm³/s |
| Reference | US Gallons per hour (gal US/h) | Cubic centimeters per second (cm³/s) |
|---|---|---|
| A domestic shower | 142.653 gal US/h | 150 cm³/s |
| A kitchen tap | 158.503 gal US/h | 166.667 cm³/s |
| A garden hose | 237.755 gal US/h | 250 cm³/s |
| The Amazon river | 1.98763 × 1011 gal US/h | 2.09 × 1011 cm³/s |
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 cubic centimetre per second is a unit of volumetric flow rate equal to one cubic centimetre passing a point every second. Its symbol is cm³/s, and because a cubic centimetre is exactly a millilitre, the same rate is often written mL/s. It sits in the gap between the laboratory and the workshop: small enough to measure with a syringe, large enough to see.
Physiology uses it constantly. Resting cardiac output of five litres a minute is about 83 cubic centimetres per second, urine production is roughly 0.017, and a quiet breath moves perhaps 500 cubic centimetres over two seconds. Because the human body deals in volumes of this order, medical devices from ventilators to infusion pumps are calibrated in it.
Gas flow measurement adopted it early. A rotameter — the tapered glass tube with a float that appears on every laboratory bench — is graduated in cubic centimetres per second or per minute, and the float position gives the flow directly. Since a gas expands, such readings are meaningful only when the temperature and pressure are stated, which is why standard conditions accompany them.
Engines make an instructive example. A four-stroke engine of 2,000 cubic centimetres running at 3,000 revolutions per minute draws air through its intake at 1,500 cubic centimetres per revolution, or 75,000 cubic centimetres per second at 100 per cent volumetric efficiency. The mass air-flow sensor in the intake measures a quantity closely related to this, and the fuelling calculation depends on it.
Laboratory chromatography and analysis are specified here as well. A gas chromatograph column carries carrier gas at one to two cubic centimetres per minute, while a detector's make-up flow may be twenty or thirty, and the ratio between them determines the shape of the peaks the instrument reports.
The unit's convenience comes from the size of the cubic centimetre itself. A thousand of them make a litre, so a thousand cubic centimetres per second is a litre per second — a bath filling in about two minutes. Anything a person can pour by hand lies within a factor of a hundred of this rate.
One cubic centimetre per second equals one millilitre per second, 0.001 litres per second, or 60 cubic centimetres per minute.