Water conversion units: 1,000 litres = 1 m3 = 220 UK gallons
When calculating water consumption remember to be consistent with units
so that you are always comparing like with like.
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 |
|
| 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 |
|
| 1" hose |
1 m3/hour |
|
| 2" pipe |
4.2 m3/hour |
|
|
Cost of water (2006 - 2007)
|
|
| 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.
|
|
Sample calculation of water use
|
|
| |
Calculation |
Example |
|
| Event |
|
hosing the floor |
| Flow rate |
F |
measured 1.8 m3/hour |
| Length of event |
T |
measured 2 hours |
| Volume water/event |
V |
F x T 3.6 m3 |
| Frequency of event |
Q |
measured twice a day |
| Daily total |
TotalD |
V x Q 7.2 m3 |
| Daily flow |
TotalD |
7.2 m3/day |
|
Some practical water saving tips are available in the Top tips section
of WaterNet
Good Practice Guide (GG522) Cost-effective water saving devices and practices
provides practical tips on how to save water in commercial and industrial
organisations.
