| Cubic inches per hour (in³/h) | Gallons per hour (gal/h) |
|---|---|
| 1 Cubic inch per hour | 0.00360465014991 gal/h |
| 2 Cubic inches per hour | 0.00720930029982 gal/h |
| 3 Cubic inches per hour | 0.0108139504497 gal/h |
| 4 Cubic inches per hour | 0.0144186005996 gal/h |
| 5 Cubic inches per hour | 0.0180232507495 gal/h |
| 10 Cubic inches per hour | 0.0360465014991 gal/h |
| 20 Cubic inches per hour | 0.0720930029982 gal/h |
| 25 Cubic inches per hour | 0.0901162537477 gal/h |
| 50 Cubic inches per hour | 0.180232507495 gal/h |
| 100 Cubic inches per hour | 0.360465014991 gal/h |
| Reference | Cubic inches per hour (in³/h) | Gallons per hour (gal/h) |
|---|---|---|
| A domestic shower | 32952.8 in³/h | 118.783 gal/h |
| A kitchen tap | 36614.2 in³/h | 131.982 gal/h |
| A garden hose | 54921.4 in³/h | 197.972 gal/h |
| The Amazon river | 4.59143 × 1013 in³/h | 1.65505 × 1011 gal/h |
The cubic inch per hour is a unit of volumetric flow rate equal to one cubic inch passing a point every hour. Its symbol is in³/h. Since a cubic inch is a little over a tablespoon, an hour at this rate produces a small puddle — which is exactly why the unit belongs to slow losses, slow doses and slow wear rather than to transfers.
Seepage and weeping are its natural subject. A mechanical seal on a pump is allowed a small permanent leakage to lubricate its faces, and the specification is written in cubic inches per hour on American equipment. A packed gland on a valve stem is similar: a few drops an hour is correct operation, and a dry gland is a gland about to score its stem.
Oil consumption in engines is quoted this way in the imperial world. A large stationary engine's cylinder lubrication is metered at a few cubic inches per hour per cylinder, and the acceptable rate of oil loss past the rings on a diesel is expressed the same way. Because such engines run for thousands of hours between overhauls, an hourly figure is what turns into a drum of oil on the purchase order.
Slow-fill and top-up systems live here too. An automatic battery-watering system, a coolant make-up line, a header tank feeding a boiler and a chemical dosing pump on a cooling circuit all move volumes of this size, and their design lifetime is set by the reservoir divided by the hourly rate.
Corrosion, erosion and permeation figures convert into it when a rate must be given as a volume. A seal that permits so many cubic inches of refrigerant per hour, or a hose whose wall passes so much fuel vapour, is compared against a regulatory limit written as an annual figure, and the hourly rate is what the test bench actually measures.
The relation to larger units frames it clearly. There are 231 cubic inches in a US gallon, so one cubic inch per hour fills a gallon in about ten days, and 61 cubic inches per hour is roughly a litre per hour. A flow that takes a week and a half to fill a milk jug is the very definition of a rate you watch rather than use.
One cubic inch per hour equals about 16.39 cubic centimetres per hour, about 0.01667 cubic inches per minute, or about 0.004329 US gallons per hour.
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.