Book - School of Science and Technology

Secondary outflow and return pipework 601Secondaryflow,returnand CWFPumpCylinderControlvalveReversed return primary circulationFigure 21.2 Dispersed indirect cylinders with central-source primariesFeedcisternFeed andexpansionVent over cisternShowerBasinBathCylinderSinkFigure 21.3 A dead-leg systemTable 21.2 Maximum insulated lengths of uninsulated hot water pipesOutside diameter of pipe (mm)Maximum length (m)12 20Over 12 and up to and including 22 12Over 22 and up to and including 28 8Over 28 3The current Water Regulations require that a hot water system is designed to ensurethat a minimum temperature of not less than 50 C is achieved within 30 seconds after atap is fully open. For energy conservation the Water Regulations also recommend themaximum lengths of uninsulated hot water pipework indicated in Table 21.2.