When a major fire broke out at a toxic waste management plant in Tuas last month, PUB engineers monitored the water supply to the hydrants to ensure firefighters had enough water to combat the blaze.
They also tracked drainage flows in the area, to check if any contaminated water from the fire was flowing to parts of the sea from which nearby desalination plants were drawing water.
They did so with a sophisticated real-time monitoring system in the national water agency's control centre, nestled somewhere in the Environment Building in Scotts Road.
The centre has 12 large screens and 16 smaller ones mounted on the wall, and many more on rows of consoles manned by engineers.
The screens display information on Singapore's water infrastructure in real-time - from detailed maps of water pipes and valves, to data on water pump pressure, flow rates and water quality. Set up in 2012 as part of PUB's Water Systems Unit, the control centre also draws information from other government agencies, like the National Environment Agency's weather radar.
When there is heavy rain and sensors in the canal warn of flooding, PUB engineers can take direct control of the Land Transport Authority's (LTA) traffic surveillance cameras via a console and joystick, to monitor and better manage the flood.
It is reminiscent of a scene in spy movie Jason Bourne, where the US Central Intelligence Agency takes control of the surveillance camera system in Athens to track down the renegade agent played by actor Matt Damon in real-time. "But we have LTA's permission," Mr Bernard Koh, the water agency's director of Water Supply (Plants), said with a laugh.
The Republic's water network is dispersed islandwide - from desalination plants in the west to reservoirs in the forested interior and the Changi Water Reclamation Plant in the east, linked by thousands of kilometres of drains and pipes.
All of it has to be monitored round-the-clock by at least one engineer and two assistant engineers in the control centre, to ensure the system runs like clockwork.
Mr Koh recalled getting occasional phone calls at 3am when there were plant disruptions due to equipment failure.
His staff needed him to assess the risk and decide how to respond.
The 47-year-old can securely log in to the system from anywhere using his iPad. "You check that the water levels at the affected service reservoirs are still okay, and how long you need to recover the plant (that supplies water to them). If you cannot do it by next morning's peak water use at 6am, you need other plants to come in and augment the supply," he said.
Water flows between plants and service reservoirs via multiple routes, making the system robust to the failure of any one part of it.
Mr Koh said his gynaecologist wife understands his occasionally erratic schedule, as she sometimes has to rush to hospital at odd hours too. "Both of us get called in the middle of the night," he quipped.
The centre's Web-based information technology also allows engineers to keep tabs on the water pipes buried in the ground.
There are 5,500km of potable water pipes and 3,500km of sewage pipes, including those extending to offshore islands such as Jurong Island and Sentosa, which are connected to the Singapore's main water grid. The potable water pipes are equipped with sensors that measure subtle changes in water pressure over time. This data is transmitted back to the control centre and compared to a baseline using data analytics, to detect anomalies that could indicate leaks.
Meanwhile, sewage pipes are equipped with sensors that detect chokages, allowing PUB to send men down to clear them before the sewage overflows onto the streets and becomes a health hazard.
For Mr Koh, water is a way of life. Although he is constantly on the alert for things like changes in the quality of reservoir water, he still finds it soothing to take a stroll with his daughter at MacRitchie Reservoir. "You can't really get away from water wherever you go, be it a drain, a (sewer) manhole, people using water. Water is part and parcel of our lives," he says.