Planning for water efficiency will help you to identify where water is used in your business,
and identify areas to save water. Having a good understanding of your operations will also help you to identify opportunities to improve your use of energy and materials and achieve further environmental and economic benefits.
A water balance can be used to show where water is being consumed and to map how it is entering and leaving your site. The time and effort needed to produce a water balance will be dependent on the size of your site and the complexity of the processes being investigated. To decide how detailed your water balance should be, consider the potential benefits versus the cost:
- what is the likelihood of identifying cost-effective opportunities to save water?
- how much money could you save?
- how much will it cost to investigate water use in more detail?
For sites with significant water consumption, the potential savings will be more than sufficient to justify drawing up a detailed water balance.
The first step is to complete an initial review of your site to gather baseline data on annual water use and costs, and identify any gaps in data or knowledge. Remember to consider all elements of water use, wastewater and effluent that leaves the site. You should aim to account for 80 per cent of the water you pay for.
Identify the location of the water meter on site and make sure that the meter reference on your bills matches the serial number on the meters. If you are unsure how to read your water meter, contact your water supplier for help. Use your bills, combined with any data on pump heating, chemicals, operational, labour and maintenances costs to estimate the annual cost of water for your organisation.
Use the following checklist during your initial review to help you think about the how each process of activity uses water. You may find it helpful to draw a simple pictorial representation of your site to visualise where water enters the site, is used and water or effluent leaves.
Next, add the detail of your review to your block diagram. Make sure you mark the major uses of water by type of activity or process, location of water meters, and points of water entry or wastewater exit. Arrows can help show flows, and connect processes.
After completing your block diagram you should now be able to quantify water use, typically measured in m3/day. Water use can be quantified in a number of ways. These are:
- direct measurement using flow meters or a bucket and stopwatch;
- calculate from other measurements;
- calculate from manufacturers’ published information;
- calculate from typical use information; and
- estimate from knowledge of the operation, process or use of equipment.
Sum all your incoming water supplies, and then sum your site outputs to produce an initial water balance. In theory, the total of all inputs should equal the total of all outputs, whether for individual operations or the whole process; this, however, is rarely the case in practice. If there are large discrepancies check your calculations – are you comparing like with like, are your meters reading correctly, are any leaks and losses all identified and accounted for?
Further information on measuring water and effluent flow to produce a water balance can be found in good practice guide tracking water use to cut costs. You are now ready to identify and prioritise water saving opportunities. Have a look at the Reduce Water use Factsheet and Top tips here.