nRF9160 cellular IoT module detects leaks in water pipes
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7Sense has partnered with the Norwegian Municipality of Horten to implement its nRF9160 SiP-powered leak detecting system to reduce water waste and meet sustainability goals.
Water waste is a critical global issue, with countries around the world grappling with both the environmental and financial consequences. Fresh drinking water, in particular, is increasingly valuable, as over 2.2 billion people around the world already have no access to “safely managed drinking-water services” (that is, uncontaminated, on-site, and freely available water sources).
And it’s not just large-scale losses that are of concern – up to 30% of the world’s water supply is lost simply due to inefficient usage and leaks. This is perhaps less surprising in the context of the cumulative effect of small losses over time – a faucet that leaks at a rate as low as one drop (approximately 0.05 mL) per second can result in a loss of more than 1,500 litres of water each year.
While technology has shown incredible promise in its ability to detect leaks and provide continuous monitoring in otherwise inaccessible areas, there are still a number of challenges that must be addressed.
Sensitivity and ultra-low power
“As water supply networks are typically located several meters underground, any monitoring devices must be equipped with highly sensitive radio modems and designed for ultra-low power consumption,” explains Jan Einar Nornes, the project manager at Smart City Horten – a Norwegian municipality that has adopted a smart water monitoring solution to combat water loss from leaks. “This helps extend the time between having to replace them in these difficult-to-reach locations.”
To help address this issue, Norwegian company 7Sense has created a powerful sensor network for detecting leaks in drinking water systems. Powered by the nRF91 Series SiP, these sensors employ highly sensitive microphones to monitor the acoustic levels of the water pipes, continually recording a broad spectrum of audio frequencies to identity potential anomalies.
From there, the data can be transmitted to the Cloud platform for analysis via the SiP’s robust cellular connectivity. The SiP’s highly sensitive modem supports both SIM and eSIM, as well as 23 dBm output power and -114 dBm RX sensitivity in NB-IoT mode for a healthy link budget.
“For the final product, we aim to support a hybrid communication setup using both NB-IoT and LoRaWAN technologies,” continues Nornes. “Like many larger municipalities in Norway, we operate our own LoRaWAN network for collecting water consumption data. Reusing this existing infrastructure could lead to significant cost savings as we scale up – potentially deploying between 500 and 1,000 sensors across our medium-sized water network.”
Enabling early intervention to minimise water loss
This solution has already been trialed in Horten, a municipality in Norway’s Vestfold county. In partnership with 7Sense, local authorities have implemented these sensors into the drinking water network. By enabling the early detection of leaks, technicians can quickly intervene before significant water loss occurs.
“The microphone head is mounted onto water pipes or valves using a strong magnet,” says Frode Stensaa, the CEO at 7Sense Technologies. “This design not only simplifies installation but also helps minimise the risk of accidental displacement during maintenance.
“However, factors such as rust accumulation can weaken the magnetic hold, and inadvertent contact by service personnel may also cause the sensor to shift. To address this, the final version will include a three-axis accelerometer to monitor orientation and detect any changes in position.”
Norway has one of the highest water leakage losses in Europe, with the country experiencing an average loss of 30% due to leaks in 2021, with some water supplies losing over 40% of their purified drinking water.
In line with its sustainability targets, Horten Municipality has deployed these devices to help reduce water loss to 18% by 2028. Encouragingly, over the past three years, the system has consistently recorded leakage rates between 16 and 17%. The initiative aims not only to maintain this progress but also to drive further reductions by pinpointing small, otherwise undetectable leaks – especially those occurring within private service connections.
The Norwegian Institute of Public Health (NIPH) has also provided support for the project, as even these smaller leaks have the potential evolve into ones – causing significant pressure loss across the network and creating an intrusion point for potentially contaminated water to enter the system. This then poses a health risk once normal water distribution has been restored.
“The advantage of continuously monitoring noise levels in the pipes is that the noise is often strongest early in the leakage phase with a clear high pitch,” explains Nornes. “As the leakage grows the noise levels tend to decrease and it’s harder to distinguish from background noise. The solution was deployed early in 2024, and while it’s still early we have detected at least one leak so far.”
The data is then transmitted to the Municipality’s Cloud platform, where advanced analytics and machine learning (ML) algorithms are used to identify anomalies as they emerge over time. By creating a large network of sensors, these algorithms can use this data for accurate analysis and to identify anomalies that may indicate a potential leak. This allows Horten Municipality engineers to respond promptly to investigate issues and minimise potential water loss.
“We’ve developed a simple visualisation platform that displays the geographic locations of sensors within the test area, alongside time-series plots of key parameters,” Nornes says. “This allows users to visually monitor noise levels detected by each sensor, with any sensor registering unusual activity highlighted in red on the map.”
Extended battery life
Because of the challenging deployment location, these sensors must also be able to operate for extended periods without the need for cell recharge or replacement.
“Frequent battery replacements would be both cost-prohibitive and extremely logistically difficult, which is why battery life is so key in this application,” explains Stensaa. “The device is powered by a D-size lithium primary battery cell, offering a battery life of more than five years.”
Battery life is aided by the nRF91 Series SiP’s support for both PSM and eDRX power saving modes, allowing it to sleep for longer periods of time and conserve power.
“We have worked with Nordic and the nRF91 Series since the introduction of the [nRF9160] in 2018,” says Stensaa. “The level of integration, Arm processor, NB-IoT modem, and well-known SDK [software development kit] – alongside the radio sensitivity and low power consumption – made the Nordic module a clear choice for the sensor.”
By identifying and addressing leaks at an early stage, cities can conserve vital water resources while also reducing the environmental, financial and infrastructural impact of prolonged losses. This proactive approach plays a key role in preserving one of our most precious resources.
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