Conserving one of the planet’s most precious resources was the focus of a recent interdisciplinary study into domestic showering in the UK. The results are part of a widespread program to move the country towards a better water-saving regime.

Water use through showering has increased in the UK and is predicted to double over the next 20 years.

Indeed, the trend for consumers to wash more than once a day using high-flow fittings has resulted in water and energy expenditure for showers exceeding that for baths.

This comes at a time when proposals by the Department for the Environment, Food and Rural Affairs recommend a reduction of UK water use from about 150L (39.6 gallons) per person per day to 120-130L.

A recent study by Liverpool John Moores University (LJMU) combined technical evaluation, a consumer focus group and home trials to examine water saving in the shower. The study assessed the main physical performance criteria of different shower types, customer attitudes to showering and the results of home trials using water-saving devices.

“We conducted the study in collaboration with United Utilities, a big water and sewerage infrastructure company in the North West of England,” says Dr David Phipps, who managed the project on behalf of LJMU.

“As part of its social responsibility program United Utilities was looking at water saving – particularly how it is affected by showering.

“The study aimed to establish three things: what people thought about water saving and showers; technical aspects of how the shower works and its influence on ‘the shower experience’, which is to do with water flow, distribution and droplet size and how it affects comfort; and which ways of restricting water flow work best in terms of the shower experience.

“For this last part we conducted tests in volunteers’ homes.”

The study recognized that water use varies greatly according to the type of shower used, and it aimed to investigate how clever shower design can meet the twin expectations of efficiency and performance.

It found that electric showers, which constitute 46% of installations, have typical flow rates of only 3-8L per minute (0.8-2.1gpm). Flows are inherently low and it is not usually possible to modify the showerhead or the flow, as this may damage the heating unit.

Mixer showers without pumps, and pumped showers, are increasingly popular but have heavier flows – in some cases up to 20L per minute (5.2gpm) – but these can be restricted by fitting a flow regulator or water-saving showerhead.

“The report found that mixer and pumped showers tended to use more water, electricity and carbon than washing by bath,” Phipps says.

“This was attributed the flow rates of these types of showers, and the fact that the frequency and duration of showering was much greater than for bathing because of the ease of taking a shower.

“The water use per minute for different types of showers was compared with bath use, which is still relatively high in the UK compared with countries like Australia. The report noted it was difficult to accurately determine the relative use of baths and showers for personal washing.”

Data collected by the study was used in estimating average annual use of water, energy and carbon in the home for each method of personal washing. The findings of the report will help to determine strategies that will encourage efficiency.

To understand consumer expectations of ‘a good shower’, LJMU organized consumer focus groups selected by age and socio-economic status from the North West region of England.

Respondents indicated that in order to wash and enjoy the experience of showering they wanted a good flow at the right temperature. It was important to have sufficient flow of water to cover the body and keep warm.

There is an increasing trend towards showering twice a day because of the convenience of the shower.

“What we found were specific generational differences,” Phipps says.

“Young people have longer showers and shower more frequently. People in this demographic have a positive attitude to environmental issues and want to contribute, but they don’t always make the connection between ‘green awareness’ and having shorter, less frequent showers.”

The laboratory work conducted by the university investigated the flow rate, spray pattern, temperature and skin pressure for 20 showerheads or flow restrictors, as these variables were considered to be the main physical parameters affecting user satisfaction.

It was found that a deliberately restricted flow rate could have implications for shower comfort, even though there was only a weak correlation between flow rate and a temperature drop from showerhead to floor. Reduced comfort can lead to longer showers in an effort to feel warm and clean, countering the efficiency gained by restricting the flow.

“For the purposes of the study we used a flow restrictor that fits inside the pipe of the shower head or a new aerated showerhead designed to give a lighter flow,” Phipps says.

“The volunteers were less happy with the flow restrictor than with the aerated showerhead. It may be because flow restrictors are not always compatible with the shower system they are plumbed into, and this can reduce the comfort of
the shower.”

In 2006 the British group Arup conducted a UK Government-backed research project looking at the physics of shower performance and efficiency (covered by WPR last year).

“What Arup did was to develop the Computational Fluid Dynamic model,” Phipps says.

“Arup used data from our laboratory experiment to validate its model, because it’s no good having a model unless you can be sure it matches real data.

“Most people are broadly in favor of being ‘green’ and saving water, but they don’t always connect this with water use through their shower habits. It’s a matter of educating the public about the benefits of installing efficient showerheads that don’t change the shower experience dramatically.

“The UK is not as developed in the area of water saving and recycling as countries like Australia, but it is moving that way.”