1. Rainwater Harvesting For Domestic Use InBachelor of Engineering Technology Building Services Engineering IrelandCathal McDermottDublin Institute of Technology2012 CIBSE AWARDS

2. Contents What is Rainwater Harvesting? Irelands climate Water Usage Types of rainwater harvesting systems Components of a rainwater harvesting system Case studies Conclusion 3. What is Rainwater Harvesting? Rainwater Harvesting is atechnology used forcollecting and storingrainwater from rooftops,land surfaces or road 4. Irelands Climate Irelands climate is influenced by the Atlantic Ocean On average it rains 188 days of the year Rainwater harvesting is ideal for Irelands high level of rainfall 5. Water Use in Ireland 6. Types of RainwaterHarvesting SystemsIndirectly pumped systemDirectly pumped systemsGravity fed systems 7. Indirectly Pumped System 8. Directly Pumped Systems 9. Gravity Fed Systems 10. Components of a Rainwater Harvesting SystemRunoff delivery systemTreatment of WaterStorage tanksCisternControls 11. Runoff Delivery SystemRainwater is transferred to the storage tank through: Gutters Downpipes The downpipes and gutters have to regularlymaintained This ensures that the maximum amount of rainfall canbe transferred to the storage tank Typical storage tank size 2-4m 12. FiltersInline downpipe filters & Subsurface Vortex filter: Treatment of Water 13. Treatment Filters Continued of WaterFloating FilterSituated in the storage tankProtects the pump and 14. Treatment of Water ContinuedFiltersUltraviolet disinfection Removal of bacteria from the rainwater. No residual effect on the water. Situated in the distribution pipework 15. Storage TanksRainwater can be stored in several ways:1.Water barrel 2.Over Ground tanks 3.Undergroundtanks 16. ControlsThe control unit for a rainwater harvesting system shouldincorporate Control pumps Insufficient rainwater control monitor High level alarm 17. ControlsFloat switch 18. Case studies for rainwaterA review of a study into the potential Case study 1harvesting in Ireland as an alternative to mains watersupply undertaken by a team in DIT led by Dr. Sean OhOgain Aims of the study1. To see if the harvestable rainfall collected could meetthe toilet demand of the house2. To evaluate the economic basis of installing a rainwaterharvesting system for the householder 19. Case Study 1Rainfall, harvestable rainfall and toilet demand between March 2006-March 20082006 J F M A M J J A S O N D TotalRainfall mm9131982810419280114 112695.5HarvestableRainfall (m)4.6 1.551.4 0.5 2.1 4.645.8 5.7 35.2Toilet Demand(m) 0.7 1.110.5 1.110.6 0.9 0.8 0.88.52007 J F M A M J J A S O N D TotalRainfall mm 12 71581038419.8 833821 4584509.8HarvestableRainfall (m)0.6 3.6 2.9 0.5 1.9 2.1 0.5 4.2 1.9 1.1 2.3 4.3 25.9Toilet Demand(m) 0.7 0.6 1.1 0.7 0.7 1.110.810.8 0.7 0.8102008 J F M A M J J A S O N D TotalRainfall mm120 3853 210.6HarvestableRainfall (m)6.1 1.9 2.7 10.7Toilet Demand(m) 0.7 0.6 0.31.6 20. Case Study 1Economic Analysis of Rainwater harvestingInstallation costs of rainwater harvesting systemRainwaterItem 2m tank installationFittings2012Precast reinforced Concrete Tank 650Installation Costs 525Total Capital Costs 3,188 21. Case Study 1Economic Analysis of Rainwater harvestingEstimated cost benefit forrainwater harvesting facilityGrant ( based on % ofMain water charge per 1,000 litres (m) 1.002.433.00with 2m storage tank capital costs)Estimated payback period (years)(yrs) (yrs)(yrs)50% 23.51675% 96.680% 7 595% 13.510.7 22. Case study 2Financial savings to suppliers of waterDetails of Study:4 Bedroom HouseSingle flush cistern -9 litre cistern -7.5 litre cistern -6 litre cisternDual flush cistern- 6/4 litre cisternTypical 5 flushes a dayCost of treatment of water taken at 0.34/m3 23. Case Study 2Single flush systemsSingle Flush Toilets Volume of flush (litres) 97.5 6 No. of people per house44 4No. of flushes per day55 5Daily water usage per household using Dual flush system (litres)single flush system180 150 120 Dual flush toilets Volume of flush No. of people per houseRatio of flushesVolume of high flush (litres) 64 1Volume of low flush (litres) 44 4 Daily water usage per household using single flush system (litres) 88 24. Case Study 2Water savings for treatment of water to a potable standard Water savings Type of cistern 9 litres7.5 litres 6 litres 6/4 litresDaily water usage per household (litres)180150120 88365 x 180 365 x 150 365 x 120 365 x 88 Annual water usage (litres) 65,700 54,75043,80032,120 Cost of treatment of water per (/m )0.34Annual cost of water per household () 22.35 18.62 14.89 10.92Annual cost of treatment of water for all 4 bed private homes in Ireland (243,303) ()5,437,822 4,529,085 3,623,268 2,657,063 25. Conclusions Water suppliers have financially the most to gain fromdomestic rainwater harvesting Rainwater systems are not a viable economic option for thehomeowner due to the relatively poor pay back period For rainwater harvesting systems to become a viableeconomic option for householders, there will need to begenerous aid in the forms of grants or other schemes fromthe government to promote the installation of rainwaterharvesting systems in Ireland 26. Thank you