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Pressure Management

Pressure Management is one of the fundamental elements of well-developed non-revenue water and leakage reduction strategy. The rate of leakage in water distribution networks is a function of the pressure applied by pumps or by gravity.

 
Relationship between the leakage and pressure

A well thought out pressure management program also reduces the frequency of water main bursts.

 

  • The higher the pressure, the higher the leakage

  • The relationship is complex, but it is generally accepted that the relationship will be linear (at worse). For example, a 10% reduction in pressure would leak >10% reduction in leakage

  • Pressure level and pressure cycling strongly influence burst frequency

  • Advanced pressure management techniques can be employed so that pressures are managed at off-peak periods thereby ensuring sufficient pressure is provided for customers at peak periods

Activities to commence pressure management

To assess the suitability of pressure management in a specific DMA or network, operators should first carry out a series of activities:

 

  1. Identify potential zones, installation points, and customer issues through a desktop study and use of hydraulic models (or digital twins)

  2. Identify customer types and control limitations through demand analysis

  3. Consider any legislative requirements (for example, for fire fighting)

  4. Gather field measurements of existing flow and pressure. Pressure needs to be collected at the inlet, average zone point (AZP), and critical pressure points (CPP)

  5. Model potential benefit using specialized hydraulic models

  6. Determine the control valves and control devices that will be used to implement the strategy.

  7. Model correct control regimes to provide desired results. In more modern times, advanced algorithms can be used which utilize AI and Machine Learning to optimize the operations of pressure managed zones

  8. Analyze the costs and benefits

There are a number of methods for reducing pressure in a reticulation system, including variable speed pump controllers and break pressure tanks. However the most common and cost-effective is the automatic pressure reducing valve or PRV.

Installing Pressure Reducing Values (PRVs)

PRVs are instruments that are installed at strategic points in the network to reduce or maintain network pressure at a specific level. The valve maintains the pre-set downstream pressure regardless of the upstream pressure or flow-rate fluctuations (flow modulated PRVs).

 

It is common that PRVs are usually set up next to the flow meters. The PRV should always be downstream of the flow monitoring point so that turbulence from the valve does not affect the flow device accuracy. It is good practice to install the PRV on a bypass pipe to enable future maintenance works.