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Wessex Water Water Efficiency Trial Report (2009)

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This report outlines a water efficiency trial that Wessex Water undertook together with Somer Community Housing Trust, the Environment Agency and Resource Futures. The trial involved assessing the uptake, effectiveness and costs of different water efficiency activities in 24 blocks of social housing flats in Bath. Blocks were split into four groups, each receiving different educational and technical water-saving measures. Uptake rates amounted to 45% for dual flush devices and 50% for engagement activities. Where interventions took place, up to 14% less water was used. The device interventions appear to be more effective than educational engagement.

EXECUTIVE SUMMARY

This report outlines a water efficiency trial that Wessex Water undertook in conjunction with Somer Community Housing Trust, the Environment Agency and Resource Futures in 2008/09. The trial involved assessing the uptake, effectiveness and costs of different water efficiency activities in 24 blocks of social housing flats in Bath.

The blocks of flats were split into four groups comprising four or five blocks:
Group 1: Devices only – water saving devices installed free of charge
Group 2: Devices and engagement – both education and devices were offered to the flats Group 3: Engagement only – visits made with educational information
Group 4: Control – no visits made to the blocks.

Water use in each block was monitored before and after the interventions using meters and data loggers programmed to record flow at 5-minute intervals.

Uptake rates for the interventions were high. 45% of the flats targeted for device interventions had Ecobeta dual flush devices retrofitted and 50% of householders in the flats targeted for engagement activities participated in discussions about water efficiency in their home. These uptake rates are higher than have been found in other studies and it is thought that this is because householders in social housing are used to tradesmen visiting their homes and so were particularly amenable to the interventions. The uptake for a Water Saving Day in a village hall which was organised as part of the educational interventions was, however, very low (two attendees from 156 invitations to the event). This further suggests that the residents were most receptive to water efficiency messages if they are presented to them and require minimal effort to receive.

Data analysis of average water consumption shows that 11 out of the 13 blocks where interventions took place used less water following the interventions. Changes in water use in these blocks ranged from -14% to +4%. In contrast, only three out of eight blocks in the control group exhibited reductions in water use over the same period and overall changes varied between -14% and + 12 %. These finding suggest the interventions were effective in reducing demand.

The device interventions appear to be more consistently effective than educational engagement. Four of the five blocks fitted with Ecobetas showed a reduction in water use which averaged 6.3%. The four blocks which received only the educational engagement visits also show a reduction in consumption however the savings are generally less. Three of the four saw changes of -2.4% to -5.2% although the fourth block recorded a change of -13.9% which appears to be an outlier in the dataset.

The cost benefit analysis, although not conclusive owing to variability in some of the results, indicates device installation alone cost £0.81 per litre saved per day, engagement alone cost £0.78 – £1.62 litre saved/day and devices and engagement together cost £2.03 litre saved/day.

The largest cost component for each of the interventions was staff time either for plumbers to install the devices or social marketing specialists to engage in educational activities with householders. These costs could be reduced by carrying out multiple interventions in a single visit, or by arranging for Housing Associations to carry out installations at the same time as their routine maintenance visits.