High pressure showers help save water, new research finds

droplet of water

A more satisfying shower could be the answer to water conservation, says Rachel England.

Minimising water consumption is a key focus in the quest to conserve natural resources and mitigate the impacts of climate change, but experts now say that swapping to more powerful high-pressure showers could actually help to save water.

Researchers from Swansea, Surrey and Bristol Universities installed sensors in 290 showers around the University of Surrey Campus. Over the course of 39 weeks, they gathered data on more than 86,000 individual showers, including information on average shower length and water flow rate.

The findings revealed that at any given flow rate, higher-pressure showers were associated with lower water consumption. While low-flow showers delivered less water than high flow-rate showers, high-pressure showers delivered less water overall because they were turned off sooner.

According to Ian Walker, a co-author of the study and professor of environmental psychology at the University of Swansea, these results point to an important showering behaviour. “It suggests that people turn the shower off when they have achieved a desired sensation, not just when they have completed a certain set of actions,” he said.

The researchers also installed visible shower timers in half of the showers, and found they were effective in preventing shower length from increasing as time went on. “We wonder if people ‘anchor’ on whatever is the length of their first shower, and stick to this when there’s a timer,” said Walker.

The research found that the length of the showers was “quite variable”, with the average shower taking 6.7 minutes, the median 5.7 minutes, and 50% of showers taking between 3.3 and 8.8 minutes. Showers over one hour were discounted. “Believe me, they happened,” said Walker.

Putting the findings together, the researchers saw water consumption drop from nearly 61 litres per shower in those with low pressure and no timer, to under 17 litres to those with a timer and high pressure. For showers with middling water pressures, a smart timer helped reduce water consumption by up to 53%.  “This is hot water, so there are potentially massive carbon savings here,” Walker told elemental.

According to Energy Saving Trust, showers are now the largest user of water in the home. Across Britain, we use in the order of 840 billion litres each year, and spend around £2.3 billion on heating water for showers. Hot water accounts for 875kg of CO2 emissions per household per year.

The Surrey University research shows that the 290 showers monitored by the researchers used 4.4 million litres of hot water and around 15 tonnes of CO2e (carbon dioxide equivalent) across 39 weeks. “Let’s say everyone in the country had a low flow, high pressure shower. We could save 15 or 20 litres of water per shower. That’s extremely significant,” he said. “And crucially, people wouldn’t feel like they’re going without. A lot of environmental messaging is centred around ‘giving things up’ for the greater good, but not in this case, so it’s a win-win.”

For social landlords looking to retrofit their existing housing stock, this represents a big opportunity. “Typically, there’s a big disconnect in rented properties between the person who buys equipment and the person who uses it,” said Walker. “Tenants often don’t have any control over the appliances and fixtures in their home. But if landlords are already motivated to act more sustainably, then it makes sense to install low-flow, high pressure showers that will just by their very nature save water and energy. And there’s no detrimental impact at all on the tenant.”

Walker said that the study, which is available as a pre-print and has not yet been peer-reviewed, is good news for the sustainability sector, but raises important additional questions. “We know what’s happening: high pressure showers are shorter. But why is this? Do they make it easier to rinse soap off? Do they make you feel clean more quickly? And at what point does high pressure stop resulting in water savings? More research is needed to understand the drivers here.”

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