Meeting water-efficiency regulations

Published:  10 September, 2009

Meeting new requirements for lower water consumption is not difficult and need not be expensive. Jacob Tompkins explains how.

It might not feel like it, but some parts of the UK are experiencing water shortages, and the south east of England has less water available per person than Sudan and Syria.

The current UK per capita consumption per day (daily PCC) of water is 146 l, but Defra estimates that we will need to reduce that figure to around 131 l to cope with higher water demand and reduced water availability due to climate change. Water-efficient new homes will play an important role in meeting these targets.

Looking outside the UK 13 other European countries manage with a lower daily PCC than the UK, including Belgium at 107 l, so the new Part G of the Buildings Regulations target of 125 l is clearly realistic and achievable So, too, are the higher levels of the Code for Sustainable Homes (CSH).

Waterwise East works with homebuilders and developers to help deliver water efficient buildings that work for the end consumer. The recently launched website* captures the lessons learned over the past two years and provides a valuable resource to anyone looking to develop a water efficient building.

So how can the CSH and Part G targets ó be met?

For a new build PCC is calculated is through the Water Calculator for new Dwellings, which uses information provided by manufacturers about flow rates and capacities of the fixtures and fittings specified in the new home and applies use factors for each appliance to calculate an estimated water consumption for each appliance, which is then totalled to give a whole-house consumption. The calculator methodology is the same for CSH and Part G, but Part G adds 5 l per person per day for external water usage to the CSH total.

Research commissioned by Waterwise East examined which water-efficient products consumers were happy to accept and which they were less keen on. The study found that consumers are happy with water-efficient showers and dual-flush toilets, but less keen on the idea of a water-efficient bath. Full details of the research are available on the website.

In terms of cost-effectiveness, the best way to start a water-efficient new home is to ensure that the products specified are as efficient as possible while still delivering effective water services.

One manufacturers (Grohe) estimates that there should be no additional cost to meet CSH levels 1 and 2 (equivalent to the Part G requirements) and an additional cost of around £125 for CSH levels 3 and 4 (105 l per person per day). Grohe predicts that with economies of scale this extra cost will be reduced to around £12.50.

Taking these two factors into consideration, it is possible to specify a home that meets level 3 of the CSH in a consumer-friendly way through smart specification.

A dual-flush toilet such as a Twyford Galerie Flushwise will only use 4 or 2.6 l per flush, and a Mira Eco shower will get you clean with a flow of only 7.5 l/min.

For taps, consider their function within the room. There is no need for a high-flow tap in a cloakroom that will only be used for hand-washing, so go low (e.g. 2.2 l/min). In a kitchen, however, it is more important to be able to quickly fill a kettle, so make sure flows are higher (e.g. 6 l/min). Bristan offer a range of taps with various flow rates suitable for all uses within the home.

As the contribution that baths make to overall water consumption is relatively small when a shower is also available, it is possible to specify a medium-sized bath (around 155 l) to satisfy consumer demand whilst still achieving code ratings.

Default settings for dishwashers and washing machines can be assumed in the Water Calculator, as most developers would not actually supply these. Using the specifications outlined above, it is possible to achieve a whole-building CSH performance of 93 l per person per day. For full details of this specification, as well as listings of other water-efficient products, see the website.

Rainwater and greywater should be considered as a last option. They are costly, both in terms of finance and in terms of environmental impact, as there is high embedded energy associated with the systems. However, for levels 5 and 6 of the CSH, rainwater and/or greywater harvesting would need to be employed to meet the 80 l per person per day requirements, with much higher associated costs.

Achieving a good score on the Water Calculator is a good starting point, but there are others areas that should be considered in water-efficient design which are not included in the Water Calculator. These include considering the layout of fixtures and fittings to minimise dead-legs and smaller pipework to supply appliances.

A variety of innovative technology is available, such as 2-stage taps (not considered in the May 2009 version of the Water Calculator) and a shower that maintains temperatures whilst switched off to enable the user to turn it off whilst lathering up ó without being bombarded with cold water afterwards.

It is also worth keeping watching out for new products. For example, Leeds University has been developing a washing machine that only uses a cup of water! In the future, you may even want to consider technology that is not currently socially acceptable (such as composting toilets) but may become the norm in our water-stressed-future. Jacob Tompkins is director of Waterwise *Special thanks go to EEDA, the Environment Agency and Anglian Water, which have provided funding and expertise to get the water-efficient-buildings website up and running.

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