Water Journal : Water Journal July 2012
water efficiency refereed paper 60 JULY 2012 water technical features Abstract Sydney Water monitored the performance of rainwater tanks installed in new homes for more than 12 months. The tanks were found to reduce household drinking water demand on average by about 21%. The energy required to run the tank systems was found to be similar to that for recycled water production. For many households, a choice of better-performing pumps could halve energy use. Introduction The environmental sustainability of rainwater tanks as a water solution for large cities depends on their ability to save water while using minimal energy. In the largest detailed rainwater tank monitoring study in Australia to date, Sydney Water remotely monitored rainwater tank water and energy use at one-minute intervals for more than 12 months for 52 real-life installations. The study's principal objectives were to confirm that rainwater tanks in real-life installations save water as expected and, if they did not, to identify opportunities to further increase water savings and reduce their pumping energy use. Method Monitored households were newly built homes, on average two years old, that had installed rainwater tanks as part of compliance with NSW's Building Sustainability Index (BASIX) water regulation requirements. These households were located all over the Sydney basin, as shown in Figure 1. The households that made up the sample were recruited using a phone survey and a $50 voucher was provided to the participating households to encourage program take-up. Data were collected for the 52 households between July 2009 and June 2010. Meters were installed (as shown in Figure 2) to measure and log at one-minute intervals, including rainwater tank-connected demand (Meter A -- which includes total demand from any non-potable end use connected to the rainwater tank); top-up (Meter B); pump energy demand (Meter C); and, for calibration and comparison, total household mains water use (Meter D). M Ferguson Household drinking water demand was found to be reduced by 21% A 12-MONTH RAINWATER TANK WATER SAVINGS AND ENERGY USE STUDY FOR 52 REAL LIFE INSTALLATIONS SydneyCBD MINTO ST ANDREWS HARRINGTON PARK ROSSMORE HOXTON PARK WEST HOXTON PRESTONS VOYAGER POINT CARINGBAH OYSTER BAY COMO PUNCHBOWL ROSELANDS KINGSGROVE BEXLEY BRIGHTON-LE-SANDS NORTH BALGOWLAH SEVENHILLS DEE WHY FRENCHS FOREST EASTWOOD EPPING CARLINGFORD CASTLEHILL GREYSTANES WENTWORTHVILLE SANS SOUCI CANLEY VALE CHESTER HILL FAIRFIELD MASCOT NORTH PARRAMATTA ENGADINE RYDE ALLAMBIE CHIPPING NORTON WEST PENNANT HILLS LANECOVE MILPERRA NORTHMEAD OATLEY EAST HILLS Figure 1. Location of households in the study. Switching device (optional ) Outdoor tap (s) Toilet Washing machine (cold) Float valve (optional ) Potable Water Rain Water Optional Connection Pump Meter D Meter B Meter A Meter C Other household uses (shower , hot water etc ) Logger Figure 2. Individual household monitoring set-up.
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