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Engineering Week: Alan Gaines Explains Distribution System Water Pressures

“What is my water pressure?”

That is a very simple question that can also be very important to Charlotte Water’s customers. Alan Gaines, Senior Engineer with Charlotte Water, explains more in-depth about the water pressure across our distribution system.

utility technician wearing orange safety vest positions a large metal wrench to open the top of a yellow fire hydrant

If the water pressure is too low, customers may have trouble performing basic tasks such as washing clothes or dishes. However, water pressure that is too high can make some tasks, such as taking a shower, uncomfortable, or cause damage to pipes and appliances.

Charlotte Water serves all of Mecklenburg County with over 4,500 miles of water mains. Pressures will be dependent on where the customer’s service is in our system. Customers should expect to see a range of pressures that can occur throughout the day. This is because water pressure depends on many factors such as the water supply pumping into the water system, water levels in the system’s elevated storage tanks, and water use by other customers.

graphic depicting flow of water through underground pipes from pumping station to water tower to customers' homes

The elevation of a customer’s home is also a major factor in their water pressure. Customers in low-lying areas, closer to creeks and streams, can expect higher pressures than neighbors on top of a hill or along a ridgeline. Because of topography in our Charlotte Water’s service area, pressures could be 40 psi or lower in some areas of higher elevation and well above 100 psi in areas with lower elevation.

Distribution System Recorded Pressures chart:

Chart titled in grey font, Distribution System Recorded Pressures. Beneath appear 2 graphs, one red and the other, blue. On the left in grey font lists, Pounds per Square Inch -PSI with tiers of 0, 20, 40, 60, 80, 100, 120. Across the bottom are time increments: 1pm, 7pm, 1am, 7am, and repeated and beneath them is the legend Location A for blue lines and red line for Location B

If a customer is concerned about their water pressure, they should consult with a licensed plumber or they can measure their water pressure themselves (many home hardware stores sell gauges that attach to a hose spigot).

Based on the plumbing code, if a customer or plumber finds a reading above 80 psi, then the customer should consider having a pressure-reducing valve (PRV) installed to protect their plumbing. A PRV is a small bell-shaped device that is typically installed right after the water meter or at the home’s shut-off valve to bring pressures to an optimal level for domestic use. This is important to help protect the customer’s appliances and maintain the life expectancy of the customer’s private plumbing. PRVs should be checked periodically and may need to be replaced on a frequency similar to a water heater tank (10 to 15 years on average).

Addressing a customer’s low water pressure concerns is a more complex process because there are multiple potential causes. Because of this, customers will likely need to contact Charlotte Water customer service and a licensed plumber to help evaluate the issue and develop an appropriate solution.

If the low-pressure cause is due to the customer’s ground elevation, then Charlotte Water will be unable to help in most circumstances. Pressure is created by adding energy to the distribution system, typically with a pump. Utilities can only add so much energy into the system without creating problems for other customers or making significant changes in major water infrastructure.

If the low pressure occurs during the customer’s water use, then there is likely a restriction between the water main and the plumbing fixture in the home. Customers are responsible for infrastructure past the meter and Charlotte Water is responsible for the meter and service line to the water main. A restriction’s location will determine which party is responsible to address the issue.

Diagram titled, Charlotte Water Water Service Connection illustrates how water connects from water main under a residential to a home. The grey and blue water main pipe buried underground connects via pipe notated with grey caps font as the Hydrant Line to the area between the curb and sidewalk to provide water to a yellow fire hydrant located outside the home. Another grey blue pipe called a Service Line runs underground and then turn upwards connecting via what is identified in grey caps font as an Angle Value to a semi-buried grey box in the ground notated with grey caps font as a Meter Box. The water then connects out of the box via a grey part called a Tail Piece and then continues through the grey and blue pipe into the how, connecting in the basement or crawl space via a large value, this is notated as a Shut Off Valve. Between where the Tail Piece appears and the blue grey pipe resumes the journey of the water to the house, a black dotted line is indicated. To the left of the line is all the plumbing that is the responsibility of Charlotte Water. Everything to the right is the responsibility of the homeowner. The Charlotte Water logo in black font appears in the lower right corner of the page.

“What is my water pressure?” This simple question has a complex answer involving multiple factors. Water pressures for Charlotte Water customers will occur in a range dependent on conditions in the Utility’s system as well as the customer’s plumbing.

 

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