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Useful Facts and Figures

How to convert units of volume, flow rate and weight

To convert from:

To:

Multiply by:

Volume

litres

cubic metres

0.001

cubic metres

litres

1000

UK gallons

cubic metres

0.0045

US gallons

UK gallons

0.8327

UK gallons

litres

4.5

Flow rate

UK gallons/hour

cubic metres/hour

0.0045

UK gallons/minute

cubic metres/hour

0.2727

UK gallons/second

cubic metres/hour

16.36

cubic metres/hour

litres/second

0.278

litres/second

cubic metres/hour

3.6

Weight

cubic metres of clean water

kilograms

1000

litres of clean water

kilograms

1

Typical rates of water use

Item

Average water use

Employee (full-time, no canteen)

25 litres/person/day

Employee (full-time, with canteen)

40 litres/person/day

Toilets

6 - 9 litres/flush

Leaky tap (continual 5mm stream)

60 litres/hour

25mm hose

1 m3/hour

50mm pipe

4.2 m3/hour

Cost of water (2008 - 2009)

Water type

Cost

UK mains supply

£0.60 - £1.60/m3* (standard metered tariff)

Chlorinated water

£0.85 - £2.20/m3

Softened water

£2 - £3.70/m3

Demineralised/
deionised water

£2 - £3.70/3

Condensate

£5 - £7/m3

Steam

£20 - £22/tonne

* Depends on mains water supplier

How to measure flow

  • If sub-meters are installed, take readings over a set time period.
  • If flow-meters are installed, take readings.
  • Use a bucket and stopwatch approach. It is simple but effective.
  • Consider purchasing or hiring sub-meters and/or flow-meters in order to calculate consumption or flow data for key equipment or process lines.