One of the first things you should do when measuring your water consumption is to take water meter readings. Water meters report on the quantities of water consumed, generally in cubic meters(m³) or cubic feet (ft³). They can provide you with a detailed view of the quantities of water consumed on your site(s).

First, you’ll need to find your meter. Generally, you will find your water meter near the boundary of the property, where the water supply enters the site. If you’re not able to find your meter, you should speak with your facilities manager, maintenance staff, or your water supplier. Please be aware that your business may have multiple water meters if there are different water sources for various areas of the site.

Once you’ve located your meter, you can take readings. You can do this by looking at the numbers showing on the face of the meter. Once you’ve taken your reading, record it so that you can keep track of the business’s water consumption. You can download the Measuring and Monitoring Spreadsheet to keep a record of these readings.

The more frequently you measure your consumption, the easier it will be to identify opportunities for improvement. Frequent meter readings will show you any short-term fluctuations in your water consumption. It is recommended that you take these readings at least once a week or every two weeks at the same time of day. However, this frequency should be increased if you are carrying out any water efficiency improvements. Taking readings morning and evening can also help you to identify any leaks by assessing the usage when no one is on site overnight.

Water bills can be a great source of information on your business’s water consumption. It is recommended that you review at least two years of water and sewer/effluent data to understand your business’s water use and costs.

Water bills tend to be more complex than energy bills, and this is because they include a number of different charges. Here you will learn how to understand your water bill. Below are some of the most common charges you might see on your water bill:

1. Water charge: this is what you are paying your water supplier to provide you with water. This will vary depending on what country or state/province your business is located but could include a standing charge (a flat rate imposed by the supplier for providing the water) and/or volumetric charge (the amount of water you have actually used).
   
   If you are billed on the amount of water used, your supplier may be estimating your water use unless you are providing them with meter readings. You should check that your bills are based on actual meter readings (if this is how your supplier bills you) rather than an estimated usage. This won’t apply to water suppliers that only charge a standing rate.
   
   
2. Wastewater / sewer charge:  this is the charge for the processing of wastewater that leaves your site and ensures that this water safely re-enters the environment. Like the water charge, this could be a standing charge (billed at a flat rate) and/or a volumetric charge. There may also be a charge based on the contents of the effluent. The volume of wastewater is usually not metered, so some assumptions will be made by your water supplier. In the US, for example, it is generally assumed that all water entering your premises will be leaving the premises as discharge into the sewer. In the UK, the wastewater volume is generally assumed to be 95% of your consumed water volume. If you think that less water than this is leaving your business as wastewater (for example, if most of your water usage is as a raw material for use in your products or as evaporated water if used in a cooling tower), then you should contact your water supplier. You may be eligible for a deduction of your bill.

1. Drainage charge:  in some countries, you may have to pay a charge that covers the cost of surface water/storm water drainage (water that runs from properties into outdoor drains). This will be unmetered and so it may be a standing charge or based on the value or size of your business property.

Your water supplier might provide you with historic data which may highlight any trends in your water use and can help you to track progress against any reduction targets and efficiency initiatives.

If you want or need to measure the water consumption or wastewater of a specific line of production or activity, then direct measurement is a very useful method of measurement. This can be done by using a clamp-on flow meter, which can be rented or bought. These flow meters measure the instantaneous flow of water through pipes as well as recording the total consumption. Clamp-on flow meters use ultrasonic technology, which means they are non-invasive and there is no need to cut into pipework.

Alternatively, you can manually calculate the flow rate to or from water-using equipment/activities over a specific time period. This involves collecting water or effluent in a container and timing it with a stop-watch. You may need to undo a pipe connection to allow the water or effluent to flow from the pipe into your container. It is recommended that you consider any health and safety requirements while doing this.

Once you have timed the water or effluent flowing into your container, measure the volume of the liquid collected (in liters or gallons). Then you can use the below calculation to measure the flow rate:

Flow rate (liters/gallons per second) = volume of water or effluent collected (liters/gallons) divided by the time (in seconds) taken to fill the container.

Ideally, you will be monitoring your water use regularly by taking meter readings and/or measuring water consumption directly. However, sometimes this isn’t practical, and you may only be able to take meter readings occasionally. In this case, you will need to make estimates where there is missing information. You can do this by sampling.

Sampling is where you take a small sample of meter readings and scale them up to be able to generate an estimated total consumption for a longer time period than you have readings for. Some tips for this methodology are below:

• It is best to collect as many meter readings (and for as long a time period) as possible. This will make sure that your estimated consumption is as accurate as possible.
• Make a note of any assumptions that you make when you are scaling up your data (e.g. 340 production days a year – compared with 365 days in a calendar year)
• Take meter readings over a representative period (e.g. a whole day/month/production cycle)
• Make sure to take samples regularly to monitor any fluctuations in your water consumption.

Although bills and meter readings can provide you with valuable information about your site’s water usage, they don’t give you detailed information on where the water is used in your production. To find this out, you can develop a water mass balance. This can be in the form of a diagram or table that shows the movement of water through your site (examples below). It works on the principle that the amount of water entering a site must be equal to the amount of water leaving the site, either as effluent, product, evaporation, or as a leak. Constructing a water mass balance will allow you to find out what volume of water is used in each water-using activity in your business operations, as well as how much effluent is leaving the site. It can also help to identify expensive leaks!

Your water mass balance should be able to account for a large percentage of your on-site water use, ideally 90%. If this is not the case, consider whether meter readings were taken correctly, any recycled/re-used flows were identified correctly, losses are all accounted for, and all leaks have been detected.

You will need to collect some information to be able to produce a water mass balance. This might include:

• Water bills (ideally at least two years’ worth)
• Sources of incoming water
• Locations, numbers, and sizes of water meters
• Diagrams or images of plumbing and water pipes
• Lists of water-using activities/processes
• Any information on water outputs that are not included in your bills (e.g. wastewater that is discharged through separate permitted discharges, or wastewater collected in tanks)

*in the above example, 12m³ has not been accounted for in the ‘water out’ column. In this case, you would want to check for leaks as the water has not left via any of the other outputs. Please note that you might not be able to account for 100% of your water usage and output but you should aim for at least 90%.

Once you have a water mass balance, you will have a much better understanding of where water is used in the business, what activities are producing wastewater, can detect any leaks, and identify areas with the greatest cost saving potential.