Mannamead is one mile north-east of Plymouth City Centre and comprises 1,532 domestic properties, with an increasing student population. The network has 9.2 km of largely pre-War, cast-iron mains, and receives its supply from Bellivere Reservoir via a 100 mm Cla-Val pressure reducing valve. The average night flow of 26 m3/hr indicates high leakage.
Monitoring at the critical node revealed a 20 m pressure drop at peak demand, whilst pressures in the lowest parts of the district were as high as 51 m. The system showed a night-to-day swing of 47 m to 19 m, giving scope for 28 m of modulated pressure reduction. Two large consumers were identified, one drawing water on a continuous basis at low flow rates and one drawing water via a fast operating electric valve.
- Boundary valves inspected and confirmed closed
- Installation of data loggers at six strategic points within the district
- Critical node monitoring
- Initial investigations by the leakage team to identify large consumers
- Detailed monitoring of large consumers
- Installation of Technolog’s pressure controller to modulate pressure in line with flow
- Night flow reduced by 15 m3/hour, representing a net night flow of 4.8 litres/property/hour
- Excess pressure removed at the critical node and at intermediate monitoring points
- Water savings of 188 m3/day achieved through the use of advanced pressure control
- Savings represent a marginal cost saving of over £3,000 per year
- Over 50% of the savings were achieved between midnight and 7 am