Water savings in shopping centres: how to cut costs and improve efficiency

Water savings in shopping centres depend on three points: the air-conditioning cooling tower, the food court and the toilets. At Shopping Center Vila Velha, in the Brazilian state of Espírito Santo, studied at the Federal University of Espírito Santo (UFES), these three added up to 76% of consumption, and half of all the water went to uses that do not need drinking water. Cutting costs and gaining efficiency in a shopping centre means tackling these three points and replacing drinking water with an alternative source wherever it is not needed.

In short:

• In the centre studied, the cooling tower took 31% of the water, restaurants 30% and toilets 16%.
• In other shopping centres cited in the same study, the food court reached 38% and toilets 40%: the profile changes, the three largest consumers do not.
• In the tower, raising cycles of concentration from 3 to 6 cuts make-up water by 20%, according to the US Environmental Protection Agency (EPA).
• Half of the centre’s water went to non-drinking uses. Treated greywater, rainwater and the water condensed by the air conditioning would cover 84% of that demand: 46,000 m³ less a year bought from the utility.
• The dye test found leaks in 29 of 54 toilets, but the loss came to 0.1% of consumption. In a centre with up-to-date maintenance, the challenge is keeping it that way.

Where does a shopping centre’s water go?

To air conditioning, food and toilets. Researcher Fernanda Guzzo measured, activity by activity, the consumption of Shopping Center Vila Velha, with a hypermarket, food court, cinema and events area, which totalled about 9,250 m³ a month:

Use	Share of consumption	Where the savings are
Cooling tower	31.0%	Cycles of concentration, blowdown control, non-drinking make-up water
Restaurants	29.8%	Efficient pre-rinse spray valves, washing without running water, metering per shop
Toilets and washrooms	15.6%	Efficient toilets and urinals, automatic taps, flushing with reclaimed water
Supermarket	7.8%	Its own meter and cleaning and preparation routines
Shops	6.0%	Metering per shop and aerators
Other uses (cinema, events, beauty salon, laundry, gym and others)	9.9%	Metering and tracking

The numbers vary from one centre to another, but the top three repeat. In the São Paulo studies gathered by the author, the tower accounted for 14% to 20% of consumption, restaurants for 30% to 38%, and toilets reached 40%. In a study of the Rio Sul centre, in Rio de Janeiro, cooling accounted for 24%.

How do you save water in the cooling tower?

By controlling how much it throws away. The tower cools the air-conditioning water by evaporating part of it, and evaporation leaves behind salts that must leave through blowdown, the water that is discharged. The EPA, which identifies cooling towers as the largest water use in many commercial and institutional buildings, at 20% to 50% or more of consumption, recommends:

1. Meter make-up and blowdown. A meter on each line shows how much the tower uses and allows the cycles of concentration to be calculated.
2. Raise the cycles of concentration. Many systems run at 2 to 4 cycles, and 6 or more may be possible. Going from 3 to 6 cuts make-up water by 20% and blowdown by 50%.
3. Automate blowdown by conductivity. The controller measures the water’s conductivity and opens the blowdown only when it passes the set point agreed with the water treatment company.
4. Treat the water. pH, alkalinity, hardness, microbial growth and corrosion need to be controlled, or the cycles cannot rise without damaging the equipment.
5. Use an alternative source for make-up. Tower water does not need to be drinkable, and at the centre studied by UFES the tower was the largest of the demands that do not require drinking water.

How do you cut water use in the food court?

By metering each restaurant and changing how washing is done. A commercial kitchen spends most of its water on washing: according to the EPA, the pre-rinse spray valve, the one that removes leftovers before the dishwasher, accounts for nearly a third of the water in a typical commercial kitchen. In the United States, valves made before 2005 run at up to 17 litres per minute, and those sold today use at most 4.8.

The centre does not run the kitchens, but it sets the rules:

• A meter per shop. With each restaurant’s meter read every month and billing by consumption, whoever wastes pays, and tenants gain a reason to save.
• A technical standard for fit-outs. The tenant fit-out manual can require efficient pre-rinse spray valves, aerators and lower-consumption equipment.
• A washing routine. Scraping leftovers before rinsing, not thawing food under running water and washing floors with a squeegee and bucket, not a hose.

The kitchen measures, one by one, are in water savings in restaurants.

How do you save water in a shopping centre’s washrooms?

By looking after the flushes, because that is where almost all the water goes. In the washroom the UFES research metered separately, far from the food court and with sensor taps, the washbasins took only 4% of consumption; toilets and the drinking fountain, 96%. In a São Paulo shopping centre, near the food court, washbasins reached 27%.

• Efficient toilets and urinals, with adjusted valves and frequent maintenance.
• Sensor or self-closing taps, especially in washrooms near the food court, where washbasins weigh more.
• A monthly dye test. At the centre studied, 29 of the 54 toilets in one group of washrooms were leaking. The loss was small, the author says, probably because the building was new and had periodic maintenance, and it is routine that keeps leaks small.
• Reclaimed water for flushing. Since almost all washroom water goes to flushing, that is where an alternative source pays off most.

How much of a shopping centre’s water can come from reuse, rain and condensate?

Up to half, in theory. At the centre studied, the demand that does not need drinking water (tower, flushing and washing) came to about 50% of consumption. The research calculated how much each alternative source would cover:

Alternative source	Volume available	Share of the non-drinking demand covered
Treated greywater, from washbasins and similar uses	About 11,300 m³ a year	20%
Water condensed by the air conditioning	About 3,500 m³ a year	6%
Rainwater from the roof	About 65,000 m³ a year in potential	118% on paper, with shortfalls in dry months
All three together, with the existing tanks	46,300 m³ a year	84%

Rainwater alone would cover the whole demand on paper, thanks to the centre’s huge roof, but it would fall short in five months of the year, when it does not rain enough. Together, the three sources cover 84%, and the centre would stop buying 46,000 m³ a year. A curious detail from the study: each ton of refrigeration of the air conditioning condenses about 5.8 litres of water a day.

Reuse requires design, treatment, pipes separate from drinking water and maintenance, and rainwater follows the Brazilian technical standard for non-drinking uses, NBR 15527. That is why reuse comes after the basics: metering, leaks and efficient fixtures.

How do you measure and keep up water savings in a shopping centre?

With metering by activity and an eye on the small hours. The UFES research installed meters on each major use and tracked consumption between 2 and 5 a.m., with the centre closed, to estimate leaks. It is the same method that works day to day:

1. Meters by activity: tower, food court, washrooms, supermarket, shops and technical areas.
2. Daily and night-time consumption: with the centre closed, whatever the meter records is a leak or a forgotten use.
3. Monthly indicators: consumption by activity and by shop, compared with the same month of the previous year.
4. A maintenance routine: testing toilets, adjusting tank float valves and reading the tower water treatment reports.

The full roadmap, from quick measures to ongoing management, is in the guide to water savings for businesses.

How does T&D help shopping centres save water?

With SEA 360º, which serves shopping centres and large commercial complexes in two phases. Implementation, with no construction work, covers the baseline under the IPMVP protocol, efficiency technology at points of use, electronic leak detection, repairs and maintenance training. In ongoing management, T&D tracks consumption and delivers monthly reports on financial, operational and ESG performance. The ceiling observed in the full programme is a 70% reduction, and each centre’s result is calculated against the building’s own baseline.

TDRR remote monitoring tracks reservoirs, pumps and hourly consumption, with alerts by app, text message or WhatsApp, and GCI handles the monthly reading of each shop’s meter, with a photo of every reading. After the first results, SEA+ uses the savings generated to fund larger projects, such as reuse and rainwater harvesting.

Frequently asked questions

What uses the most water in a shopping centre?

The air-conditioning cooling tower or the food court, depending on the centre. At Shopping Center Vila Velha, the tower took 31% and restaurants 30%. In São Paulo studies, the food court reached 38%. Washrooms come right after.

Can a shopping centre bill each shop for its water use?

Yes, with a meter per shop and the rule set out in the lease or internal regulations. A documented monthly reading, with a photo of each meter, avoids disputes and gives tenants a reason to save.

Can reclaimed water be used in the cooling tower?

Yes. The tower does not need drinking water, and at the centre studied by UFES it was the largest of the demands that do not require it. Water quality must be controlled together with the water treatment company, to avoid scaling, corrosion and microbial growth.

Does a shopping centre’s air conditioning produce water?

It does, by condensing moisture from the air. At the centre studied, each ton of refrigeration condensed about 5.8 litres a day, adding up to nearly 3,500 m³ a year. It is little next to total consumption, but it is water that can supply the tower or the toilets.

How do you know if a shopping centre has a leak?

By reading the meters in the small hours, with the centre closed, and by running the dye test on the toilets. Night-time consumption above the usual pattern signals a loss. The step by step is in invisible leaks: find them before the bill does.

Sources

• Guzzo, F. R. Strategies for conserving drinking water by using non-potable sources in a large commercial building. Master’s dissertation, Federal University of Espírito Santo, 2017, in Portuguese: consumption by activity at Shopping Center Vila Velha, leaks, alternative sources and comparison with other centres
• EPA WaterSense at Work, section 6.3, Cooling Towers: the share of towers in consumption, cycles of concentration and blowdown control
• EPA WaterSense at Work, section 4.1, Pre-Rinse Spray Valves (2023): the weight of the pre-rinse spray valve in a commercial kitchen
• T&D SEA 360º, TDRR and GCI