Pressure Management and AMI-MeterSYS

Advanced metering systems allow for near real-time monitoring and, thus, better management of water pressure in a distribution system. The key drivers of pressure loss include main breaks, power loss, and equipment failure. Main breaks and equipment failure are obvious contributors to pressure loss, but loss of electricity is sometimes overlooked. Energy is required to pump water through the pipes at consistent pressure levels, and power loss would impact this.

The official definition of pressure loss from the U.S. Environmental Protection Agency (EPA) is when the distribution system reaches 20 Pounds per Square Inch (PSI) or less. Pressure loss events are dangerous to the water utility because they compromise the quality of the water being released to customers, create Non-Revenue Water Loss (NRWL) events, and limit the ability of the utility to efficiently serve its customer base. For example, from a human health perspective, when pipes have breaks or openings of any kind, it can result in the back-flow of water, which brings the risk of contaminants being released into the water distribution system. The EPA has created a list of water quality problems that can occur when pressure losses are present in the distribution system. Pressure loss events can increase the risk of the problems listed in the chart below.

Table 1: Displays possible contaminants and unfavorable conditions to water quality management [1].

To avoid water quality problems, the distribution system should stay within 10% of the recommended ranges more than 95% of the time to maintain good system health. Limiting the fluctuation of pressure is important to protect the physical integrity of water, reduce energy consumption, system maintenance, and limit leakage [2].

>0 psi during emergencies

>20 psi under max day and fire flow conditions

>35 psi under normal conditions

<100 psi under normal conditions

Table 2: Displays ideal water distribution system pressures [2].

Interestingly enough, time of day can also play a role in pressure. Any leak in a distribution system conforms to a square-root equation, which allows for a leak to increase by ~40% if pressure in the distribution system is doubled. During the day, pressure is usually lower due to the increased usage, but at night, when water usage is less, pressure can build in the distribution system and cause main breaks as seen below [3]:

Figure 1: Displays the pressure build-up that can occur when water usage drops overnight in a water distribution system [3].

Pressure can be managed in these situations with Fixed Outlet, Time Modulated, or Flow Modulated pressure control in addition to system pressure monitoring. Pressure Reducing Valves (PRVs) no matter the type, essentially, are working towards limiting pressure fluctuations under multiple demand scenarios on the distribution system as seen below. A utility can deploy these in areas where pressure is a consideration in limiting damage to the water system’s infrastructure.

Figure 2: Displays the purpose of a PRV; to manage pressure fluctuations in a water system [3].

Managing pressure in a water distribution system is not an isolated objective. Pressure management works best as one element of a multi-faceted program that also includes acoustic leak detection and temperature monitoring. These sensor systems can become more impactful when interfaced or hosted on an Advanced Metering Infrastructure (AMI) system and approached as one component of a holistic asset management program. AMI can help reduce instances of undiscovered leaks through system-generated alerts and keep track of other important metrics and indicators, such as water temperature, which would compromise the integrity of the water pipes and cause new leaks.

The American Water Works Association recommends that water utilities begin with an assessment of pressure and leaks in the distribution system with about 12 months to develop a system baseline. A custom plan should be built based on the needs of the specific utility and the financial justification of installing pressure management systems should be completed as well. Following that approach, a plan that incorporates industry best practices can be deployed to improve system oversight, with the following positive results listed as key drivers and benefits:

Costs to implement the pressure management system will be minimal in comparison to system losses in an unmonitored system
NRWL will be reduced by around 10-15%
Main breaks will occur more infrequently
Energy usage reduction in pumping water

There is significant value contained within a pressure management plan underpinned with acoustic leak detection and temperature management. Advanced monitoring systems allow for the better maintenance of water quality, limit structural water loss, and protect the water utility’s long-term financial viability, while being great additions to the utility’s larger service plans. The ability of a pressure management program to help the utility run efficiently and increase service quality should be evaluated in comparison to the costs to identify a return on investment.

MeterSYS is experienced in the evaluation, design, and deployment of AMI systems and helps utilities evaluate the business case for technology acquisition.

1 American Water Works Association (AWWA), et al. “Effects of Water Age on Distribution System Water Quality.” Environmental Protection Agency (EPA).

2 LeChevallier, Mark W., et al. “Pressure Management: Baseline to Optimized Utility Case Studies.”Water Research Foundation, 2013.

3 McKenzie, R S, and W Wegelin. “Implementation of Pressure Management in Municipal Water Supply Systems.” N/A, 2009.