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
04 05 Bath capacity The Water Efficiency Calculator requires the input of the capacity of baths up to the bottom of the bath overflow. Today there are a wide diversity of bath shapes and sizes and it is possible to purchase baths from Ideal Standard with a capacity as low as 116 litres ( a typical average capacity for baths is around 190 litres). To keep water usage down it is recommended that both a bath and a shower are installed in a dwelling. If there is only one bath or one shower it will be given a very high weighting. Tap and mixer flow rates All taps and mixers inside the house are measured and they can account for high water consumption. Whether you need to reduce the flow rate on taps or mixers will be determined by the water pressure in the building. Most Ideal Standard mixers and pillar taps can be fitted with water regulators that either regulate the water into or out of the fitting. WC flush volume The calculator takes into account the amount of water required to flush WCs in the house. Modern WCs often require less water than they used to and by specifying a dual flush suite the smaller flush will be measured in a 2: 1 usage ratio - dramatically reducing the amount of water consumed. Concept Arc 55cm basin; pedestal; close coupled wc with Arc cistern; 170cm water saving bath ( right handed) with Ideal Waste System. Ceraplan single lever basin mixer, single lever bath filler.