The night shift starts at 10:30 p.m. to search for leaking water mains in Oslo, Norway.
They are the only team at the Agency for Water and Sewerage Works permanently assigned to work the graveyard shift — year round, in all weather. While the rest of the city is deep in slumber, they listen for leaks on the city’s water mains.
Leak detection never use to exist as a job in and of itself. Previously, finding leaks was based on a reaction to an already burst main.
Now due to a focus on water conservation, flood management and capital infrastructure maintenance, the city is combed nightly in a grid-like pattern. This proactive approach to identifying leaks requires two teams of six to work day and night.
The entire city of Oslo is checked once a year. The separate crews have slightly different tasks.
The daytime crew interacts with more of the general public and on occasion has to enter private homes to identify where the location of the leak. The night crew is less likely to enter homes but more likely to meet people in an altered state.
An advantage to working at night is that there is less sound from traffic and water consumption. The sounds of a toilet flushing, a shower running or traffic rumbling past can all effectively hide the faint sound of a leaking water pipe.
It is reasonable to think that leaks occur first on the oldest water pipes but the quality of the material and frequency of use often play more of a role in terms of the lifespan of a water main. The oldest known water main was constructed in 1,600 of wood.
It carried water from the main river to the fortress guarding the downtown core of Oslo. The oldest remaining water main still in service is from a much younger period of the 1890s.
Interestingly, a period of poor quality water main production was the years immediately following the Second World War. Due to the high demand for steel during the war, a shortage and poorer construction of water mains followed.
Oslo loses about 20 million cubic liters of treated drinking water annually. Leak statistics are separated between water mains, which are the responsibility of the municipality, and water pipes in homes and businesses, which are the responsibility of the building owner.
There were 233 leaks on municipal mains and 479 leaks on private mains in 2011. So far in 2012, there have been 100 leaks and 350 leaks on the latter.
There are different kinds of water “breaks” — cracks, punctures, tears, bursts, etc., which ultimately affect the repair job due to the severity of the “break.”
Oslo has a freezing depth of 1.5 to 2 metres but in the north of Norway the freezing depth can reach down to three metres. In smaller towns there is also less stress on the pipes that lead to cracked pipes because of the minimal traffic in comparison to Oslo.
In Oslo most leaks occur when the weather changes in the spring and the ground starts to defrost, which can cause the pipes to buckle and crack.
Steps to finding a leak
The city’s water distribution network is divided into zones based on water consumption patterns. Each zone is meticulously inspected for leaks with the use of a copper wand 2.5 metres long placed on the water main.
A faint hum is an indication of a leak. The team listens to the manholes on the same water main until the sound disappears. This defines the potential starting and stopping point for the leak.
Next, an electronic microphone is placed on these two end points. Within minutes the frequency signals are displayed in a graph form to a laptop where a spike in the graph indicates a potential leak. To more accurately pinpoint the location of the leak, a listening device that resembles a stethoscope is used to locate the leak.
A leak on a water main can quickly turn into an emergency — the velocity of the water can buckle roads and cause sinkholes and flooding, resulting in impassable roads and stranded people.
The leak detection team also has the job of responding to customer calls of a water leak. A leak visible to the naked eye can spell trouble quick and the fire department is brought in to close roads.
The water valve regulating the flow in the leaking main is quickly turned off while at the same time the customer service side of operations springs into action and an automated text message is sent out to all affected residents and businesses.
The leak detection team has a lot of responsibility — they have to respond quickly if there is a leak obvious to the naked eye to close roads and notify customers. And they have to be certain that it is indeed a leak they heard — and not the sound of someone flushing their toilet.
Digging up the city centre is expensive; therefore, it is always best to double check.
Sonya Jenssen previously worked for the Union Bay Improvement District and Wedler Engineering LLP in Courtenay. She is away on assignment as a project co-ordinator for the City of Oslo at the Water and Sewerage Works.