To reintroduce appropriate pressure management to this large water supply zone (WSA). Historicalpressure management regimes had demonstrated considerable volumetric savings.
The existing flow meter and old PRV were surveyed for possible service and re-use. Electromagneticflow meter was found to be non-operable and beyond repair and the old 10 PRV was seized, againputting it beyond economic repair.Flow prediction software was utilized to calculate expected flow regimes into this WSA, which contains9772 properties, predominantly domestic in nature.Flows were estimated at -: Peak flow - 287m3/hr (79.8l/s) and Min flow - 63.4m3/hr (17.6l/s). Bothestimates have used a background leakage figure of 45m3/hr.
||Replace seized old PRV with new 200mm (8”) diaphragm type PRV - note PRV has been downsizedand a different type recommended.
||Pressure logging has identified a possible 10-12m reduction in pressure with some form of modulationat night. Inlet pressure could be managed from 62m to an outlet pressure of 50m.
||A 200mm Dorot PRV was purchased mated to a Fluid Controls hydraulic modulator.
Graph 1 below demonstrates the impact of the pressure management upon the strategically locatedpressure loggers. The Critical Points (Target Point) for this WSA are Haddington Gardens, OnslowGardens and the top of Castlereagh Road. The infrastructure at Haddington Gardens is characterisedby 5” CI mains (circa 1920-1930) with poor internal condition, which at times of peak demand causesexcessive low pressures. The Castlereagh Road monitoring point is the highest and farthest point fromthe PRV at My Lady’s Road.
Graph 2 depicts flow data from Ravenhill 2 waste zone which has been permanently “zoned in” forthe previous four weeks so data could be collated showing pre and post commissioning flow regimes.The nightlines indicate a reduction in nightline of approximately 1.5l/s.k
Graph 2 - Flow results from a waste zone
Extrapolated Volumetric Savings
Logged flow data from the Ravenhill Road waste zone provided a daily volumetric total in m3/daywhich are summarised in table 1 below.
Ravenhill Road 2 waste zone contains some 1236 properties and the volumetric reduction is calculatedat 0.13mld (million litres per day).
If this volumetric saving is extrapolated over the whole 9770 properties then the calculated volumetricsavings overall is approximately 1.08mld.