Conversion from US Gallons per second to Gallons per hour

Information about the US Gallon per second (gal US/s)

The US gallon per second is a unit of volumetric flow rate equal to one United States gallon passing a point every second. Its symbol is gal US/s. The US gallon is exactly 3.785411784 litres, descended from the English wine gallon of 231 cubic inches, so one US gallon per second is a little under four litres every second.

Fire protection in the United States works at this scale. A fire hydrant flows several gallons per second, a pumper truck delivers 20 or more, and a large sprinkler system's design demand runs to tens. Fire codes state these figures in gallons per minute, but hydraulic calculations of friction loss in the mains use the per-second value, and the two are the same number divided by sixty.

Municipal water and wastewater engineering also reaches it. A neighbourhood water main carries a few gallons per second at peak hour, a lift station handles tens, and a treatment plant's influent hundreds. American practice usually states plant capacity in million gallons per day, and one gallon per second is 0.0864 million gallons per day — a conversion any water engineer performs from memory.

Industrial cooling and process water are described here as well. Condenser cooling water, quench flows and washdown systems all reach gallons per second, and the pump power required follows from the flow multiplied by the head, so an increase in flow of ten per cent shows up directly on the electricity bill.

The difference from the imperial gallon deserves a clear statement. The US gallon is about 17 per cent smaller than the imperial one, so the same numerical rate is a materially different flow on either side of the Atlantic. Equipment documentation should say which gallon it means, and prudent engineers convert to litres before comparing anything.

For scale, one US gallon per second is about 3.79 litres per second, and 0.264 US gallons per second is one litre per second. A flow of ten US gallons per second is nearly 38 litres per second, enough to fill a domestic bath in three seconds and comparable to a small stream.

One US gallon per second equals about 3.785 litres per second, about 0.003785 cubic metres per second, or about 0.8327 imperial gallons per second.

Information about the Gallon per hour (gal/h)

The gallon per hour is a unit of volumetric flow rate equal to one imperial gallon passing a point every hour. Its symbol is gal/h, often abbreviated GPH. One imperial gallon is 4.54609 litres, so this unit describes the slow, sustained flows that matter over the length of a working day rather than a minute.

Fuel consumption is its most durable use. A boat's diesel engine burns 1 to 5 gallons per hour at cruising speed, a generator 0.5 to 2, and an agricultural tractor 2 to 4. Because such engines run at steady load for hours, the hourly figure multiplied by the hours of running gives the fuel bill directly, which is why boat and plant operators still think in these terms.

Oil-fired heating uses the unit for burner nozzles. A domestic oil boiler is fitted with a nozzle rated in gallons per hour — 0.5, 0.65 or 0.85 for a house — and that rating, multiplied by the calorific value of the oil, gives the heat output. Changing the nozzle changes the output, so the nozzle size on the burner label is effectively the rating of the appliance.

Water treatment and dosing are described the same way. A softener's regeneration flow, a chlorinator's feed rate and a chemical dosing pump on a cooling system are all set in gallons per hour, chosen so that the treated water leaves the plant with the concentration the process requires over a whole shift.

Older domestic water fittings carried the unit too. A header tank's fill rate, a cistern's refill and a slow-running standpipe were measured in gallons per hour in British practice, and the same figure told a householder how long a tank would take to recover after a bath had emptied it.

For scale, one gallon per hour is about 4.5 litres per hour, and 220 gallons per hour is about a cubic metre per hour. A rate of one gallon per hour would fill a domestic bath in about eighty hours, which is a fair reminder that this unit measures processes, not deliveries.

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