What is water loss?
Water loss is the amount of distributed drinking water that does not reach customers, and that water utilities therefore do not receive payment for. This is also known as non-revenue water (NRW).
- the amount of water lost due to e.g. ruptures and leaks in the pipeline grid and reservoir overflows (also knows as physical losses)
- unauthorised consumption, such as illegal tapping and meter inaccuracies (also known as apparent losses)
- authorised consumption used to flush pipes at new installations and during repairs, water used for fire fighting and sprinkler systems checks, etc. (also known as unbilled authorised consumption)
Water loss is often either calculated as the percentage og total distribution or as cubic meters per network kilometre per annum.
Denmark has implemented systematic measures to reduce the loss of drinking water as it makes its way from waterworks to the consumer. Danish drinking water providers are actually among the best in the world in this area.
Water loss is a waste of resources
Water loss in Denmark is 7.8 per cent on average. In comparison, many countries lose as much as 30 to 60 per cent of their treated water before it reaches customers. This is not only an enormous waste of clean water, it is also a waste of the resources that have been used to extract the water, treat it and distribute it.
One of the reasons why Denmark is so good at keeping drinking water in the pipeline grid is that providers use new technologies, methods and knowledge. This makes it possible to measure and register water data and to quickly identify even the smallest pipeline leaks.
Another reason is that, since 1994, waterworks with a water loss of more than 10 per cent have been required to pay a penalty fee to the state. Furthermore, since 1996, all properties connected to public water utilities have been required to install water meters. This has resulted in significantly more reliable data on which to base efforts to reduce water loss.
This website provides an description of a number of these methods and technologies. Additionally, there are examples of three water utilities that have succeeded in reducing water loss significantly over the past few years by applying a systematic approach to the issue.
Overview of methods and technologies
Water utilities can use methods and technologies such as monitoring, leak detection and compartmentalisation of the pipeline grid to minimise water losses.
Quick repairs of known leaks
Even small leaks should be repaired as quickly as possible. A seemingly small amount of water at surface level can be indicative of a larger leak at the source
Proactive replacement of problematic pipeline sections
Water meters installed at waterworks and consumers can be inaccurate. Among other things, this inaccuracy depends on the type of meter and the physical installation. Meter inaccuracy can result in readings that are either too high or too low.
Monitoring exit meters at waterworks
In order to register real water loss, it is vital that the exit meters at waterworks are accurate. For example, if a meter reading is 2 per cent too high, the waterworks will suffer considerable additional costs if water wastage is already more than or close to 10 per cent. The inaccuracy can be due to the type of meter, the manufacturer, the age of the meter, dimensioning or incorrect installation on the pipes.
Even the best meters will not be accurate if the fitting instructions are not followed. There are usually requirements regarding the dimensions and length of the pipe immediately before and after the meter. The type of meter and the manufacturer can also influence the accuracy throughout the measurement area. Even though there are no requirements regarding the age of a meter, it may be a good idea to replace meters at regular intervals. Alternatively, meters can be sent for testing and adjustment in order to ensure - and document - that the meter is accurate.
All consumption meters are subject to a guideline on control systems for cold and hot water meters in operation (”Måleteknisk vejledning om kontrolsystem for koldt- og varmtvandsmålere i drift” - in Danish only). This guideline states that all meters must be approved and tested or replaced in accordance with relevant guidelines.
However, errors can still occur during the meter-installation period. for example the meter can stop registering. If the error is not detected, the lack of charges will increase water loss.
It is important to monitor and react to unusually low water consumption, which typically becomes apparent in connection with the annual meter reading. Some newer meters have built-in technology that notifies waterworks automatically if the meter stops working. In this situation, immediate follow-up is required to avoid the lack of metering being registered as water loss.
Placement of consumption meters
The waterworks distribution grid usually stops at the boundary of a property. At this point, the waterworks branch pipe is connected to the property's underground service pipe. The coupling point often consists of a branch pipe valve or a meter well. However, if waterworks meters are located in the building itself, then a leak in the underground service pipe will usually result in an increased water-loss rate for the waterworks. If the leak is detected, the owners of the property have to carry out the necessary repairs or replacement at their own expense.
Leakage from private underground service pipes can effect water-loss rates at waterworks. To avoid this, waterworks can place a water meter in a well at the border of the property. If the meter is placed at a border, a leak in the underground pipe will be detected much quicker than if the meter is placed in the building. This also means that any water loss due to leakage can be invoiced.
Meter reading frequency
Consumption meters are normally read once a year. If a property's water installation has a leak, a high volume of water might be from when the leak first occurs to when it is detected and stopped. If water wastage is registered, waterworks will usually only receive payment corresponding to "normal" consumption + 300m3. Moreover, this is a waste of resources and an unnecessary expense for the consumer.
New meter technology makes it possible to read meters more frequently. This means that leaks can be detected earlier. The same applies to the underground service pipe if the meter is placed in a well at the border of the property.
One important factor in reducing water loss is renovating pipes before leaks occur. The quality of the renovation is also important to prevent new leaks.
Old iron pipes
Since 1970, waterworks in Denmark have mainly used PE and PVC pipes in their pipeline grids, but private underground service pipes have also used iron pipes. Depending on local soil conditions, iron pipes are susceptible to corrosion and leaks. This means that iron pipes must be monitored closely to avoid water loss.
Iron pipes can be monitored effectively by placing water meters at the border of a property. Additionally, iron pipeline sections should be more closely monitored using acoustic leak detectors, pressure tests or via monitoring wells.
Asbestos pipes do not rust. However, they are vulnerable to subsidence. This means that the pipes might rupture and require emergency repairs. Handling asbestos pipes requires great care as the dust from the pipes is dangerous to inhale.
Sections with asbestos pipes with many cracks should be replaced by pipes made of a different material. This will limit water loss and simultaneously cut operating costs in connection with emergency pipe repairs.
Aluminium tapping saddles
During the 1960s and 1970s, poor-quality aluminum tapping saddles were fitted to Danish pipeline grids.
The problems became apparent 10 to 15 years later. Today, better quality saddles are used, but the old aluminum saddles are still causing problems. In addition to water loss, waterworks are burdened by emergency excavation requirements outside of normal working hours.
If the locations of the old tapping saddles are known, waterworks should consider replacing them to avoid leakage. In addition to limiting water wastage until the leak appears at the surface, the individual cost per tapping saddle replaced will be significantly reduced.
Errors can occur when laying new water pipes. These errors might not be discovered before the pipes are buried. Such errors can result in leaks that are not immediately detected because new water pipes are often placed in draining materials that delay signs of leaks on the surface. A leak could therefore remain undetected for many years and cause significant water loss.
The number of errors can be reduced by combining staff and external-contractor training with quality control and supervision during and after completion of the work. The price of pipeline work is important, but it is not more important than quality. Over the pipe's operational life of 75 years, a loss of only 1 liter per minute will result in total water wastage of 40,000 cubic meters.
Each year, excavation damage causes pipe ruptures and other damage to water pipes. This damage is usually repaired quickly, but sometimes the damage is not detected or not reported to the waterworks.
Work is carried out blind during controlled under-drilling since it is based on maps and test boreholes. Severe damage to a water pipe will cause a rupture that will require immediate repair. Less serious damage to a water pipe might cause a leak which might not be detected from the surface or via the borehole.
The risk of damaging water pipes can be reduced by thorough preparation beforehand. Among other things, this will require procuring up-to-date maps and clearing known pipes. A dialogue with local pipeline experts can also be an important part of these preparations.
Private underground service pipes
Water loss from private underground service pipes can account for a large percentage of a waterworks' water loss. The reason for this is a combination of smaller pipe dimensions and a short distance to the drain. This means that water wastage does not always become visible at ground level.
The underground service pipe can be monitored if a meter well is installed at the border of the property. Any possible waste of water resources will be registered and payment can be charged, either in part or in full. If fitting a meter well is not an option, then leaks can be detected via systematic pressure tests or leak detection on the underground service pipes.
Flushing water pipes
The water used to flush water pipes will always be included with water loss. If the flush speed is too high or if it goes on longer than necessary, then this will result in unnecessary water loss.
Water wastage can be reduced by optimising flush speeds and durations. This will save both resources and energy. Flush speeds should normally not exceed 0.5 meters a second and flushing should only last until the pipes are clean. This can be checked by taking a water sample. Flushing should be stopped or reduced until the results of the analysis are ready.
Water used for fire-fighting benefits society and should therefore not be included as water loss. Waterworks should therefore enter into agreements with municipalities that water usage in connection with fire fighting and tests must be reported. Furthermore, fire hydrants should regularly be checked for leakage.
Fire hydrant leakage
Fire hydrants -particularly older ones - sometimes leak slightly after use or testing. Dripping fire hydrants can waster up to 10 liters an hour. This corresponds to an annual 87 cubic meters of water wastage.
Waterworks should routinely consider the fire hydrants in their area and possibly inspect them at least once a year. Waterworks should also have a written agreement with the municipality regarding receiving immediate notice if the municipality discovers a leaking hydrant. In cases of water wastage, the fire hydrant should be repaired, replaced or shut down permanently as fast as possible.
Large amounts of water are sometimes used in connection with fire fighting. In order to put out a fire, easy access to the required amount of water is clearly vital. If the amount of water used is not reported to the waterworks afterwards, then it will be registered as water wastage, which is not the case.
Waterworks themselves should note incidents requiring the use of fire hydrants. Waterworks should also enter into a written agreement with the municipality that they will register and notify water consumption in connection with fire fighting. Waterworks will also be able to assess the water consumption themselves by reviewing the amount of water distributed on the day in question. The water consumption can also be read accurately at the waterworks' SRO installation. If the municipality is subsequently billed for the amount of water used, then this will not effect the water-loss rate.
Theft and other unauthorised usage
Unauthorised tapping of water from fire hydrants sometimes occurs. This may be vandalism or simply theft. It can also be a matter of ignorance if a contractor acutely needs water for his asphalt cutter or cement mixer. This is naturally completely unacceptable and should be considered theft. In addition to water wastage, this also results in wear to the fire hydrant and the risk of incorrect use which may result in damage to the fire hydrant.
Possibly in collaboration with the municipality, the waterworks can send a letter or flyer to all local builders and contractors on the rules for fire hydrant use. This should state that unauthorised use of water from fire hydrants will be considered theft. It is also a good idea to inform citizens living in the supply area of the rules.
Consumption in connection with fire hydrant testing
Water for building sites
Water consumption at a building site can fluctuate from zero to several hundred cubic meters. Many price lists charge for a fixed number of cubic meters for building water. If the consumed volume of building water exceeds the charged amount, then this amount will be registered as water loss. If water consumption at a building site is not measured, then there is little incentive to avoid water wastage during the building period.
Water consumption at both small and large building sites should be measured and charged as far as possible. It is therefore recommended that a metering point be located at the entrance to the building site, so that all water consumption during the building period can be charged. Before the water is opened, a written agreement should be made with the project developer, stating that payment can be charged in advance.
Unauthorised use of hoses
Hoses reels/fire alarm boxes are often fitted at businesses, institutions and larger housing units. Hose reels are sometimes used for other purposes than extinguishing fires or testing. Since the water used for fire extinguishing is not measured, this use will effect the wastage rate of waterworks and result in lost revenue.
Facilities with hose reels should have their own independent pipeline grid without a meter and it must be easy to access and use. By securing the box or hose nozzle with an easy-to-break seal, with regular inspection the waterworks can make sure that they are not being misused. There should be clear signs stating that the hose reel can only be used to extinguish fires and that the waterworks must be contacted immediately if a seal has been broken.
Theft before meters
Intentional tapping of non-metered water should be considered theft. The tapped amount of water will effect the water-loss rate and result in a financial loss for the waterworks’ consumers. Unintentional tapping before meters is also unacceptable and should therefore be invoiced retrospectively based on estimates by the waterworks.
In addition to general information for consumers and local plumbers, the waterworks themselves should also keep an eye out for anything unusual.
Personnel from waterworks and external fitters and plumbers should report abnormalities or suspicions of fraud that they observe in connection with replacing meters.
It may be related to a missing or defective seal on the water meter or tapping components located between the meter and the distribution pipe.
For more information
You are welcome to contact the organisations below if you would like to know more about specific technologies. They can also help you identify the appropriate advisors and suppliers.
DANVA - stakeholder organisation for drinking water and wastewater utilities as well as all professionals in the field of water and wastewater.
Danish Environmental Technology Association - the sector association for Danish environmental technology companies.
Danske Vandværker - the sector association for Denmark's waterworks.