Preston and Thomastown pumping stations – mitigating the risks of hydraulic surges

Client: Melbourne Water
Location: Victoria, Australia
Date: October 2012 – November 2013

Reviewing hydraulic transients for existing and proposed pumping stations to ensure safe and reliable water distribution.


A review by Melbourne Water of its water supply strategy recommended a change in operation for the existing Preston pumping station to meet projected water demand. The review also recommended that when demand dictates, a new higher capacity pumping station should be built at Thomastown to replace the Preston pumping station.

A hydraulic transient study was required to determine the need to develop concept designs to mitigate hydraulic transients (high or low pressure surges that can damage the plant or pipelines).


Entura was engaged to model the hydraulic networks to predict the pressure transients and recommend preferred mitigation options to Melbourne Water for both the Preston and Thomastown pumping stations. Entura liaised with Melbourne Water (water supplier) and Yarra Valley Water (water retailer) to develop the transient mitigation options including provision of pressure relief valves, surge chambers or flywheels on the pumps.

Entura identified that transient mitigation would be required for both the Preston and Thomastown pumping stations to prevent negative pressures occurring in the bulk transfer main pipeline and to meet the function requirements at the retail offtakes.

Entura developed a transient mitigation solution of providing added flywheels at the pumps to treat the transient issue at the source, without needing numerous mitigation devices at multiple locations in the transfer mains.


A major operational change in the water transfer and distribution system posed significant risks, including the risk of asset failure due to water hammer resulting from a power failure while pumps are in operation. Entura’s solution eliminated this risk by removing the source of unacceptable negative pressures resulting from sudden uncontrolled pump shutdown.

Space was available in the existing building to accommodate Entura’s pump flywheel  solution, and minimal pump upgrades were required to retrofit the flywheels. Containing the solution within the existing pumping station building avoided planning issues and land acquisition costs, saving the client time and money.

Implementation is on hold as water demand has not yet reached projected levels, but will proceed when water demand reaches the critical level.