| Liters per hour (L/hour) | Liters per second (L/s) |
|---|---|
| 1 Liter per hour | 0.000277777777778 L/s |
| 2 Liters per hour | 0.000555555555556 L/s |
| 3 Liters per hour | 0.000833333333333 L/s |
| 4 Liters per hour | 0.00111111111111 L/s |
| 5 Liters per hour | 0.00138888888889 L/s |
| 10 Liters per hour | 0.00277777777778 L/s |
| 20 Liters per hour | 0.00555555555556 L/s |
| 25 Liters per hour | 0.00694444444444 L/s |
| 50 Liters per hour | 0.0138888888889 L/s |
| 100 Liters per hour | 0.0277777777778 L/s |
| Reference | Liters per hour (L/hour) | Liters per second (L/s) |
|---|---|---|
| A domestic shower | 540 L/hour | 0.15 L/s |
| A kitchen tap | 600 L/hour | 0.166667 L/s |
| A garden hose | 900 L/hour | 0.25 L/s |
| The Amazon river | 7.524 × 1011 L/hour | 209000000 L/s |
The litre per hour is a unit of volumetric flow rate equal to one litre passing a point every hour. Its symbol is L/h. It is the unit of slow, sustained flows — the ones too gradual to watch, where what matters is how much has moved by the end of a working day rather than what the stream looks like now.
Irrigation is its clearest home. A drip emitter is rated at 2, 4 or 8 litres per hour, and an orchard is designed by counting emitters: two hundred trees with two 4-litre emitters each draw 1,600 litres per hour, so a three-hour watering delivers 4.8 cubic metres. Because the emitters run for hours, the hourly figure is the one that maps directly onto the water budget.
Fuel consumption is quoted the same way whenever an engine runs at a steady load rather than travelling. A generator burns 2 to 5 litres per hour, a farm tractor 10 to 20, a large marine diesel several thousand. Litres per hour is the honest unit for these machines because litres per 100 kilometres means nothing to something that does not move.
Heating appliances follow. An oil boiler is rated by its burner nozzle in litres per hour, typically 1.5 to 3 for a house, and the figure multiplied by the heating value of the oil gives the heat output in kilowatts. A hot-water tap that produces 8 litres per minute is 480 litres per hour, which is why the same equipment carries both numbers in different parts of its documentation.
Laboratory and process work uses the unit for pumps that must run all day. Peristaltic dosing pumps for chlorination, water treatment and fermentation feeds are specified in litres per hour, often with a turndown range like 0.5 to 20, because the point of such a pump is to keep a slow rate constant for weeks.
Leaks and losses are described here too. A dripping tap loses a few litres per hour, which is trivial in a minute and a hundred litres by the next morning. Water utilities express network losses this way for the same reason: a slow rate compounded over the hours of a year is what turns an unnoticed defect into a measurable volume.
One litre per hour equals about 0.000278 litres per second, 0.01667 litres per minute, or 0.001 cubic metres per hour.
The litre per second is a unit of volumetric flow rate equal to one litre passing a point every second. Its symbol is L/s. It is the unit of pumps, drains and ventilation — the scale at which a flow is large enough to be a design problem but small enough to belong to a single building.
A litre per second is a substantial stream. A kitchen tap fully open delivers about a fifth of it, a bath fills at roughly a third, and a fire hose runs at ten to twenty times as much. In visual terms it is a jet about as thick as a thumb moving briskly, and it would fill a domestic bath in about two minutes.
Building services are specified in this unit throughout Europe. Ventilation rates are given as litres per second per person — around eight to ten in an office, more in a room where people cook or exercise — and a designer multiplies that figure by the number of occupants to size the fans and the ductwork. The same unit describes rainwater drainage, where a roof's area and the local rainfall intensity together determine the flow a downpipe must carry.
Pumps are rated the same way. A domestic circulating pump moves a fraction of a litre per second, a borehole pump a few, and a large sewage pump hundreds. Because the power a pump needs is the flow multiplied by the pressure it must overcome, this figure sits at the centre of every pump calculation.
For gases the unit describes compressors and blowers, though there the volume depends on pressure and temperature and so must be stated at defined conditions. A compressor rated at fifty litres per second of free air is measured with the air at atmospheric pressure, and the same machine moving compressed air is shifting a far smaller volume.
A litre per second is a thousandth of a cubic metre per second, which is why hydrologists and building engineers rarely use the same unit even when they are describing the same water. A river carrying a cubic metre per second is carrying a thousand litres per second, and both figures are correct.
One litre per second equals 1,000 millilitres per second, 60 litres per minute, or about 0.0353 cubic feet per second.