| US Gallons per hour (gal US/h) | Milliliters per hour (mL/h) |
|---|---|
| 1 US Gallon per hour | 3785.411784 mL/h |
| 2 US Gallons per hour | 7570.823568 mL/h |
| 3 US Gallons per hour | 11356.235352 mL/h |
| 4 US Gallons per hour | 15141.647136 mL/h |
| 5 US Gallons per hour | 18927.05892 mL/h |
| 10 US Gallons per hour | 37854.11784 mL/h |
| 20 US Gallons per hour | 75708.23568 mL/h |
| 25 US Gallons per hour | 94635.2946 mL/h |
| 50 US Gallons per hour | 189270.5892 mL/h |
| 100 US Gallons per hour | 378541.1784 mL/h |
| Reference | US Gallons per hour (gal US/h) | Milliliters per hour (mL/h) |
|---|---|---|
| A domestic shower | 142.653 gal US/h | 540000 mL/h |
| A kitchen tap | 158.503 gal US/h | 600000 mL/h |
| A garden hose | 237.755 gal US/h | 900000 mL/h |
| The Amazon river | 1.98763 × 1011 gal US/h | 7.524 × 1014 mL/h |
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 millilitre per hour is a unit of volumetric flow rate equal to one millilitre passing a point every hour. Its symbol is mL/h. It is the unit of slow, sustained delivery, and above all of the infusion pumps that keep hospital patients supplied with fluid, nutrition and medication over many hours.
An intravenous line is almost always programmed in millilitres per hour. Maintenance fluid for an adult runs at 80 to 125, a slow drug infusion at 5 to 20, and a paediatric or neonatal line at 1 or 2. Those are the numbers a nurse enters, and the pump converts them into the mechanical rate of a screw driving a syringe plunger.
At the bottom of that range the precision required is remarkable. A syringe driver set to one millilitre per hour is advancing the plunger by a fraction of a millimetre per minute, and it must do so smoothly enough that the drug arrives at a steady concentration rather than in pulses. The engineering of these devices is largely about eliminating the stiction that would otherwise make the delivery uneven.
Insulin pumps work below this again, in tenths of a millilitre per hour, and deliver in tiny discrete pulses rather than continuously. Implanted pumps for pain medication may run at a fraction of a millilitre per day, which is a thousandth of a millilitre per hour, and are refilled at intervals of months.
Outside medicine the unit describes laboratory perfusion, slow chemical dosing, and the leakage rates that a seal is designed to stay below. A seal specified to leak less than a millilitre per hour is losing about a cupful a week, which for many purposes is entirely acceptable and for others is a failure.
For scale, a millilitre per hour would take a full day to fill a tablespoon and about a month to fill a small cup. It is slow enough that the total delivered over a shift is the meaningful quantity, and every pump displays that alongside the rate.
One millilitre per hour equals about 0.01667 millilitres per minute, 0.000278 millilitres per second, or 0.001 litres per hour.