Water Efficiency Retrofitting: A Best Practice Guide (2009)

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This is an update of the best practice guide “Water Efficiency Audit Programmes” published by Waterwise in 2008. It will summarise current best practice for water efficiency retrofitting, for those wishing to carry out large-scale projects and for companies wishing to carry out water efficiency trials to contribute to the evidence base. Drawing on experience by practitioners, it will suggest ways in which trials can contribute to existing knowledge gaps, with a particular focus on the planning phase. It seeks to reinforce the connection between company-led water efficiency retrofitting projects and the need to build an evidence base to support large-scale water efficiency.

In March 2008, Waterwise published ‘Water efficiency audit programmes: a best practice guide’and this was useful for several water companies, many of whom were embarking on their first water efficiency trials. This update to the best practice guide will summarise current best practice for water efficiency retrofitting, for those wishing to carry out large scale projects and for companies wishing to carry out water efficiency trials to contribute to the evidence base. We will do this by building on the experience gained by those who have been involved to date in water efficiency retrofitting. However it is also important that we extract further meaningful insight from the water efficiency projects that we carry out in the future.

We have learned, for example, how to carry out water efficiency in social housing through three major projects in this area: the Preston Water Efficiency Initiative, the Wessex Water – Water Efficiency Trial and the ongoing SHARE Project (Social Housing Action on Resources and the Environment). And we are already in a position to learn from these experiences how to carry out larger scale retrofitting projects in social housing in the most cost-effective way. However, there are a number of areas of uncertainty where further understanding from industrial practice, regulatory and policymaking perspectives would be helpful in driving water efficiency even further. So in this best practice guide we also suggest ways in which trials can contribute to the still-expanding Evidence Base. Some such areas that need further work are:

the water savings we can expect from carrying out water efficiency retrofitting under different scenarios such as water companies working in partnership with social housing providers, energy companies, or local energy advice providers, or piggybacking on other water company activities such as metering to deliver showerhead or toilet retrofits.

how we can carry out water efficiency retrofitting in a more cost-effective way
identifying which water efficiency devices provide most effective savings

how the water savings observed in water efficiency trials compare to microcomponent data we currently use to estimate demand
the carbon emissions reductions associated with water savings from trials

whether retrofitting multiple devices per home is more effective at saving water than a single device retrofit

Through these trials water companies are able to contribute to the body of evidence required to ensure improved regulation and policy. For example, understanding such issues could be of direct consequence to the Periodic Review, water efficiency targets and Water Resources Management Plans as well as cost benefit analysis for metering programmes. Therefore, in this best practice guide, we will place more emphasis than before on ensuring that at the end of a trial we are able to present the results needed to fill the gaps in the current evidence base.

The Evidence Base for Large Scale Water Efficiency was published in October 2008 and brings together about 20 of the largest scale water efficiency trials and clearly stating the water savings and evaluating the level of uncertainty in the savings. The trials carried out have helped water companies, policymakers and regulators start to gain a better understanding of the potential contribution of water efficiency to the supply-demand balance.