LOURES — Some 80,000 cups of water, 4,000 toilet flushes or 800 five-minute showers — that’s how much water is saved every day since the public swimming pools in Loures, a district of the Portuguese capital Lisbon, introduced a project to reuse water.
To comply with Portuguese regulations on water quality and treatment, swimming pools must discard 2% of their total water volume each day. But the Loures City Council, together with the pool management company GesLoures, came up with a better plan: Instead of wasting that water, why not store it in reservoirs and reuse it for irrigation and street cleaning?
While swimmers splash around in the pool, water continuously falls into gutters. Previously sent down the drain, this water is now filtered, treated, and redirected to reservoirs. What was once flushed away into the sewage system is now put to good use.
At the Santo António dos Cavaleiros public pool in Loures, the recycled water takes two different paths: the local parish council uses it for cleaning public spaces, or the irrigation system diverts it to the nearest garden.
Reusing to prevent droughts
With global temperatures on the rise, periods of drought are expected to become more intense and frequent in the coming years, warns Sara Correia, a water resources expert at the environmental association ZERO. “If we see a significant drop in rainfall due to climate change while demand for water stays the same — or worse, increases — the situation will become even more critical,” Correia said.
To ease the strain on water resources, solutions like urban water reuse are crucial. Correia believes we can “reuse much more than we currently do.” Across Portugal, less than 2% of treated wastewater gets reused.
While this water isn’t safe for drinking, it has plenty of other possible uses.
That’s why GesLoures Chairman Nuno Vitorino describes the water-efficiency initiative as “a drop in the ocean.” Still, he sees it as an important first step: “We’re not going to stop using swimming pools. There will always be some water waste, but we can at least reclaim part of it.”
Over the past year, GesLoures has implemented the reuse system in three public pools. Together, these facilities now save around 20 cubic meters of water per day. “For years, that water was simply wasted. What matters is that we’ve turned a corner, and now it’s being put to good use,” Vitorino says.
The water recovery tanks outside one of Loures swimming pools in 2024. Source: GesLoures via Facebook.
The journey of reused water
Sharing water management responsibilities with the parish councils has proven beneficial for everyone involved. “We’ve all realized the savings,” Vitorino says. “Especially the councils, which used to buy water — now they just come here to collect it.”
Without much fanfare, parish council cleaning trucks regularly pull up behind the pool complex to refill their tanks directly from the reservoirs. During the rainy months, water is collected less frequently. But in summer, it’s taken several times a day, says Marco do Ó, a pool maintenance technician.
He leads us into the underground section of the facility, a dimly lit, humming cavern filled with water tanks and filtration machines. “This is the part no one ever sees,” he says, “but it’s essential for the pool to function.”
But how can chlorinated water be used to water gardens?” For skeptics, he has a simple answer: after 24 hours of rest, the chlorine evaporates, making the water safe for irrigation. Dispelling myths around treated wastewater is key, says Correia. While this water isn’t safe for drinking, it has plenty of other possible uses — including, believe it or not, brewing beer.
Spreading the idea further
Students from Portela High School in Loures recently got a firsthand look at how the pool water reuse system works. “During a field trip, we explained the process and highlighted the importance of finding new ways to manage water,” says Telmo Simões, who coordinates activities for the People and Planet project in Portugal.
Funded by the European Union, the project spans 22 cities across the country, aiming to get young people thinking about ways to improve their local communities — especially regarding sustainability and water scarcity.
The initiative was well received by local teachers, who, “due to lack of time or resources,” often struggle to incorporate these issues into the classroom. One idea students from Portela High School proposed was raising awareness in the local community about how public pools are reusing water.
Looking ahead, GesLoures hopes to expand the project to Loures Public Pool. But since it sits below sea level, additional solutions will be needed to pump the water into reservoirs.
Loures was a pioneer in this water-efficiency initiative, and other cities are already looking to “tap into the idea,” says Nuno Vitorino.
