02 03 Ideal Standard guide: 4 The Water Efficiency Calculator An introduction to the new Water Efficiency Calculator which provides the way to calculate the theoretical water usage per person per day in a domestic building. The calculator requires the input of water usage data on bathroom and kitchen appliances for a new building or building that has change of use. 6 Low flush WCs Over the years WC flush volumes have reduced from as much as 20 litres in the mid 20th century down to 6 litres or less today. This section explains the options available and the factors that need to be considered in selecting the most effective flush in a building. 9 Low volume baths The bath typically uses a considerable amount of water in the bathroom. Today changing habits mean that showering has reduced bath usage. This section shows the options of baths and shower/ baths available and the water they consume. 10 Flow regulators for taps, mixers and showers For the most efficient use of water it is important to have the right balance between effective flow rate and pressure versus over- consumption of water. This section explains the considerations needed in selecting the optimum fittings. 14 Thermostatic hot water control There are different ways to comply with the new requirement to have thermostatic temperature control on baths. Here we show the different solutions that can meet this need. This guide is provided to help you quickly understand Part G and the considerations you need to make when planning a building. It is not intended to be used in isolation and we would recommend you always consult the water regulations or planning officer before specifying any project. The full Part G document can be downloaded at www. planning portal. gov. uk. The Water Efficiency Calculator document can be downloaded at www. communities. gov. uk.
How water consumption is measured The calculated consumption figure is obtained by inputting the manufacturer's stated performance, of the specified fixtures and fittings, into the official new Water Efficiency Calculator tool. The Calculator contains predetermined daily water patterns that have been identified by BRE ( Building Research Establishment). The calculator multiplies each fitting's performance against a usage figure and for certain fittings adds on a ' fixed usage' figure. The totals of all the house fittings are then added up and multiplied by a ' normalisation' factor. The sum is reduced by any positive effect from rain water or grey water recyling before being multiplied by a ' normalisation' factor of 0.91.* Finally an automatic 5 litres of water is added on for Part G conformance to cover outdoor water usage.** What is measured The following list shows which fixtures and fittings are measured to calculate the water efficiency of a house and the performance information required. WCsflushing capacity in litres ( full and part for dual flush). Taps and Mixers( inc. restrictors and regulators) full flow rate at 3bar dynamic. Bathsfull capacity to overflow ( excluding displacement). Showers( inc. restrictors and regulators) full flow rate at 3bar dynamic delivered at 37 º C. Dishwasherslitres per place setting as per energy label or assume 1.25 litres per setting. Washing machinelitres per kg of dry load as per energy label or assume 8.75 litres per kg. External tapsfixed usage of 5 litres per person per day. ( Part G only, Code is assessed under WAT 2). Part G introduces a new methodology and calculation tool, the Water Efficiency Calculator for New Dwellings. The new Calculator assesses the whole house water efficiency by using the manufacturer's stated performance against a number of generalised/ assumed water usage patterns. This calculator is used for Part G and the Code for Sustainable Homes, replacing all previous published calculator tools. The Calculator Multiple fittings It is likely there will be more than one type of fitting, such as multiple WCs, installed within a project, however the Calculator tool requires just one performance figure to be entered. Additional tools are provided with the Calculator, to determine the average performance figure for ' multiple fittings'. To encourage a consistency of water efficient products across the whole dwelling project, two methods of calculating the multiple fittings performance are required. The two derived performance figures, are then assessed against each other. The first multiple fitting calculation is the standard averagefigure. When several stated values are presented, add them all together and divide them by the number of stated values. Example: ( 8 + 2 + 5) ÷3 = an average value of 5. The second multiple fitting calculation is the weighted average. Multiply the highest performance value stated on your multiple fitting by 0.7. Example: flow rates, en- suite 8 litres per minute, cloakroom 2 litres per minute, bathroom 5 litres per minute. The en- suite tap is the highest figure so you multiply 8 x 0.7= 5.6. When you have completed the two average calculation processes, compare them - the highest value is the one entered into the Calculator. In the two examples above, the weighted figure of 5.6 is higher than the average 5, so this is entered into the Water Efficiency Calculator. With the introduction of the weighted average figure, the DCLG are ensuring that all of the fittings are water efficient and avoiding the installation of one mega-efficient product, to offset the performance of others. * Normalisation Factor: the DLGC studied a cross-section of built and occupied Code for Sustainable Homes dwellings over one year and assessed the actual usage of the water efficient fittings. The results demonstrated that the real life usage was lower than the Calculator's assumed usage. The normalisation factor reflects real time patterns as users begin saving more water through changed behaviour. ** For Code compliance level 1- 6, the 5 litres of external water use per day is not included, but section WAT 2 - External Water Use within the Code for Sustainable Homes is reverted to. Performance Target Part G Code level 1- 2 Code level 1- 2 Code level 1- 2 Maximum ' Wholesome' consumption, litres per person, per day 125 litres 120 litres 105 litres 80 litres Summary of water consumption targets for Part G and the Code for Sustainable Homes Installation typeUnit of measureCapacity/ Use factorFixed useLitres/ Flow rateperson/ day column 1x column 2+ column 3= column 4 WC single flushFlush volume ( litres) 4.42 WC dual flushFull flush volume ( litres) 1.46 Part flush volume ( litres) 2.96 WCs multiple fittingsAverage effective flushing volume ( litrres) 4.42 Taps ( not kitchen sink) Flow rate ( litres/ minute) 1.581.58 Baths ( where showerCapacity to overflow also present)( litres) 0.11 Shower ( where bath also present) Flow rate ( litres/ minute) 4.37 Bath onlyCapacity to overflow0.50 Shower onlyFlow rate ( litres/ minute) 5.60 Kitchen sink tapsFlow rate ( litres/ minute) 0.4410.36 Washing machineLitres/ kg dry load2.1 DishwasherLitres/ place setting3.6 Waste disposal unit( litres/ use) 1 or 03.08 Water softener( litres/ person/ day) 1.00 Total A Deduct contributions from grey water and rainwater ( separate calculation tables provided)- Total B Normalisation factor: ( Total A - Total B) x 0.91Total C External water use: Total C + 5 litresTotal Litres