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The hidden impact of your daily water use
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The amount of water we use in our homes can make a big contribution to our carbon footprint (Credit: Getty Images/Javier Hirschfeld)
The way we do our laundry, clean our dishes and hose down our cars all has a surprising and largely unnoticed impact on the climate.

Jackie Lambert suspects that her habit of showering only every three days is unusual. “But I’m unapologetic for it because I think it’s fine,” she laughs. After all, a daily shower is more about cultural expectations than hygiene.

To be fair, Lambert’s whole lifestyle is on the unusual side. After she and her husband were made redundant in their early 50s, they decided to rent out their house in the coastal town of Bournemouth, UK, and move into a caravan with their four dogs for much of the year. At the moment, they’re in a village in the Italian Alps.

“The limit when you’re caravanning is the fact that you very rarely have water hooked up to the caravan,” explains Lambert, who worked in sales before she retired. “You have to collect all the water yourself.”

The couple typically fill 40-litre water carriers at caravan sites, and roll them along the ground to their caravan. “It’s surprising how quickly you get through that,” says Lambert. “So, certainly, the lifestyle does make you very conscious of how much water you use.”

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A good example is laundry. The couple use a portable twin tub washing machine, an electricity-powered device with two compartments that requires a bit more manual input than a typical modern washing machine. First, they pour warm water into the left side, which runs up to 12 minutes on an agitating cycle. They then move the clothes to the right-hand tub – a spin dryer. “We re-use rinse water for the next wash if it is clean enough to do so,” explains Lambert. Though small, the gizmo can even accommodate duvet covers.

A surprising amount of carbon dioxide is released due to domestic water use as these graphs show for older homes (left) and new build homes (Credit: Waterwise/Javier Hirschfeld)

A surprising amount of carbon dioxide is released due to domestic water use as these graphs show for older homes (left) and new build homes (Credit: Waterwise/Javier Hirschfeld)

This kind of machine may be impractical for most homes. But domestic laundry has a surprisingly large carbon footprint. The power needed to run household appliances, and especially the energy required to heat up water, has a carbon footprint that’s largely invisible to householders. Yet all of our water use adds up. It accounts for 6% of all carbon dioxide (CO2) emissions in the UK, while laundry alone accounts for 8% of all residential-sector CO2 emissions in the US. The energy needed to move, treat, and use water in the US for both residential and commercial purposes produces nearly 290 million metric tonnes of CO2 annually – the equivalent of 5% of the nation’s overall carbon emissions.

For a standard new-build home in the UK, the energy used by utility companies to treat and pump water to domestic property is responsible for only about 10% of water-related CO2 emissions. The bulk of the emissions from household water use, comes from the energy needed to heat water in the home, about 46% if a gas boiler is used. About 17% of the emissions come from using dishwashers, and 11% from washing machines. In the US, about 19% of all energy delivered to households is used for heating water, while doing the laundry in each household in the country is estimated to release an average of 240kg of greenhouse gas emissions a year.

Rather than large white-goods, the kitchen sink is actually the source of the most water-related carbon emissions in the home

“Hot water is one of the bigger energy-consuming issues in a household,” says Elizabeth Shove, a sociologist at Lancaster University who researches everyday energy use. While using solar enegy to heat water can make a big dent in that, it is has high installation costs and is far from being available for everyone. Most modern homes tend to use one of two systems to heat their water – either a gas or an electric boiler.

In the majority of houses with a gas boiler in the UK, the main cause of emissions might surprise many households. Rather than large white-goods, the kitchen sink is actually the source of the most water-related carbon emissions in the home. Keeping the kitchen tap running leads to approximately 157kg of CO2 being released per year while the dishwasher produces 142kg of CO2, the washing machine generates 118kg and the bath creates 103kg. (In a newer home, however, the shower is the water-use device with the highest emissions.)

While these figures date from 2009, they are thought to be a reliable indicator of the kind of emissions that come from different water-intensive activities in the home. But there are ways of reducing that footprint.

Surprisingly, using a dishwashing machine more can help. One analysis in the US found that putting dirty crockery and utensils into a dishwasher uses less energy and less water than doing them by hand. It estimated that using a dishwasher could reduce greenhouse gas emissions from washing up by 72% compared to doing them by hand. Pre-rinsing dishes, as many people do under a running tap, can reduce these savings considerably, as can running a dishwasher that is only half full.

Washing your dirty laundry in a front-loading washing machine has been found to be better for the environment than using a top-loader (Credit: Getty Images/Javier Hirschfeld)

Washing your dirty laundry in a front-loading washing machine has been found to be better for the environment than using a top-loader (Credit: Getty Images/Javier Hirschfeld)

But for those who don’t have dishwashers, it is still possible to keep your emissions to a minimum. Being sparing with the water and using less hot water can all make a difference. Using a bowl for washing up, rather than a running tap, could save about 666kg of CO2 a year, according to one analysis – roughly the same as a return-trip flight between London and Oslo.

“We just have a plastic bowl that we would normally fill with an inch or two of water, and do the washing up in that, and rinse in clean water,” says Lambert.  “We try to use as little water as possible.”

And while very hot water can help to get rid of germs, our hands are unable to cope with the kind of temperatures needed to kill bacteria and viruses with heat alone. However, for dishes, the combination of heat and detergent will make cleaning them a lot more efficient, while leaving them to soak beforehand can also make a big difference rather than trying to blast off any stubborn food with running water.

For those looking to wash something larger than a cup or plate, avoiding running water is also generally a good rule. Using a bucket to wash the car rather than a hose can save a lot of water, energy and carbon. But one study found that using a bucket and sponge to wash a car, and then rinsing with a power washer was the most water-efficient method, using less than half as much water compared to a hose.

Lowering the temperature of the wash, combined with air-drying, could make a big difference to cleaning up your laundry-related carbon emissions

As for laundry, the most carbon-intensive part of dealing with our dirty clothes is drying them off, due to electricity-gobbling tumble dryers. According to one estimate, drying makes up about 5.8% of residential-sector CO2 emissions in the US. Heating the water for laundry accounts for a further 1.59%, while the actual washing itself makes up 0.9%.

Lowering the temperature of the wash, combined with air-drying, could make a big difference to cleaning up your laundry-related carbon emissions. As this also uses less electricity, it could also save you money.

“Cold-water use seems to be the transformation that people can make with the least effort,” according to researchers at Arizona State University who examined the carbon footprint of domestic laundry. For instance, a load of laundry washed at 60C, then dried in a washer-dryer, produces the equivalent of 3.3kg of CO2, compared to just 0.6kg for the same load washed at 30C and dried on a clothesline.

One analysis by the Sustainability Consortium estimated that if one load of laundry a week was washed on a cold cycle rather than warm or hot, each household could reduce its carbon footprint by 23kg a year. Given 26 million tonnes of CO2 are emitted in the US each year from washing clothes, it could go a long way towards reducing this.

Using a bucket and sponge is perhaps the greenest way to wash your car, but consider a power washer to rinse the suds off afterwards (Credit: Getty Images/Javier Hirschfeld)

Using a bucket and sponge is perhaps the greenest way to wash your car, but consider a power washer to rinse the suds off afterwards (Credit: Getty Images/Javier Hirschfeld)

While not everyone can be as fortunate as Lambert, who can hang her duvet cover outside in the Italian sunshine and have it dry within an hour, air-drying is feasible for many. After all, it’s common in damp Britain, and even people in humid climates frequently air-dry. One obstacle in the US, where tumble dryers are ubiquitous, is the prohibition by some homeowners’ associations of hanging laundry outside, because it’s considered unsightly. If you do have to use a dryer, using the high-speed spin cycle on your washing machine can reduce the energy needed as there’s less water to evaporate from your clothing.

Another option is to switch to a more efficient front-loading washing machine, which uses less water and energy, and is smaller, than a top-loading washing machine. The majority of washing machines in US are top-loading, creating a significant opportunity for change. According to one estimate, replacing 25% of US top-loading machines with front-loading ones could reduce electricity consumption and CO2 emissions by 5% on average.

When it comes to washing ourselves, it is obviously important to maintain good hygiene, but replacing a daily bath with a three-minute shower could save approximately 849kg CO2 per year, for a family of four.

Some showers are also less resource-intensive – mixer showers, which combine hot and cold water before the water emerges from the shower head, produce 100kg less CO2 over the course of a year than an electric shower. Installing shower heads that use less water can also reduce the carbon footprint produced by pumping the water to your home and disposing of it once it goes down the drain.

A daily bath can release a surprising amount of carbon dioxide into the atmosphere over the course of a year while showers release less (Credit: Getty Images/Javier Hirschfeld)

A daily bath can release a surprising amount of carbon dioxide into the atmosphere over the course of a year while showers release less (Credit: Getty Images/Javier Hirschfeld)

“A low-flow shower is not an oxymoron,” says Judith Thornton, a low carbon manager at Aberystwyth University in Wales. “You can get shower heads that simply spread the water around in a more efficient way. So you feel like you get just as wet, but you’re only using about seven litres a minute instead of 15.”

To give another example, shaving your legs in a wash basin rather than during a shower might use eight litres of water rather than 48, Thornton says.

In some cases the more convenient option is actually the lower-carbon one. “We’re all washing our hands for longer now,” says Thornton, noting the advice that has been issued about handwashing following the outbreak of coronavirus around the world. “You know how it is when you turn the hot water tap on, and it’s not until you’ve finished washing your hands that the water’s got hot?” If homes have narrower pipes between tanks and basins, or if pipes are better insulated, the amount of waiting time to achieve hot water can be reduced – making for energy efficiency gains as well as a better user experience.

Of course, we don’t necessarily need hot water to clean our hands properly. The mechanical action and the soap itself is responsible for cleaning our hands more than the temperature of the water. In order to kill the Covid-19 coronavirus with hot water alone, for example, it would require water temperatures above 56C (132F), which are hot enough to scald.

Hanging clothes to dry in the air rather than in a tumble-dryer can make a big dent in carbon emissions (Credit: Getty Images/Javier Hirschfeld)

Hanging clothes to dry in the air rather than in a tumble-dryer can make a big dent in carbon emissions (Credit: Getty Images/Javier Hirschfeld)

Washing our hands with a cooler, more comfortable water temperature, along with soap and a bit of elbow grease, could end up being kinder to the climate and just as hygienic.

Overall, individual water-use decisions can’t be one-size-fits-all. “It’s this funny blend of science, morality, public investment, commercial provision, the economy and working hours,” says Shove of people’s very diverse washing habits.

Thornton agrees, arguing that it’s necessary to understand why people wash the way they do, for instance, to get at how they might conserve water while also not breaching their fundamental right to water. People have different motivations for how they shower. An office worker who uses a shower to mark the start of her day, for example, might want to find another ritual such as brewing tea to get going in the morning. (Read more about the peculiar bathroom habits of Westerners.)

Governments can move things along too. For instance, encouraging the use of water meters and water efficiency labels on appliances can help people make better decisions. According to the water research and advocacy group Waterwise, if UK building regulations adopted a mandatory water label associated with a target of 85 litres per day, this would cut CO2 emissions by 55.9 million tonnes over 25 years. This would be equivalent to taking nearly a million cars off the road each year during that period.

But the good news is that some of the most impactful changes will come from tweaks to our daily habits. “The CO2 cost of water is 80% what we do with it in our homes,” says Thornton.

Just a few small changes to the way we wash could make a big difference.

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