UNDER PRESSURE: How Municipal Water Commutes to Work

Eau Claire water tower above the treeline. For the City of Eau Claire, Wisconsin, Ayres designed a 1.5-million-gallon water tank located in a west-side high-pressure zone, an area that includes two business parks.

For the City of Eau Claire, Wisconsin, Ayres designed a 1.5-million-gallon water tank located in a west-side high-pressure zone, an area that includes two business parks.

By Michael Stoffel, PE
With a mere turn of the faucet, water arrives when and where we need it so routinely that few give this modern-day miracle a second thought.

Portrait of Ayres civil engineer Michael Stoffel.

About the Expert:

Michael Stoffel, PE, is a senior project manager in Ayres’ Municipal Group with extensive experience in well and pumphouse design and modifications, and chemical feed design including instrumentation and control, water main design, and booster pump station design. He has served as project manager for Wisconsin projects including the City of Phillips Well No. 7 and tower projects in Baldwin and Prentice.

But the process of making water readily available in municipalities across the country depends a great deal on the forethought civil engineers lend to it. Water’s journey from its original source to your kitchen sink likely includes a fair number of twists and turns, along with temporary sidetracks for treatment, storage, filtering, heating, and other important reasons to pause. So how do we keep water moving in the right direction? Pressure.

What Is Water Pressure, And How Is It Generated?

Water pressure is the force applied to water in order to overcome friction, pushing it through infrastructure and fueling its momentum along the matrix of pipes on its way to your shower. This force can be created by pumps and pressure stations along the route, or in many cases through water towers, which take advantage of height, water weight, and gravity to generate adequate pressure. The taller the tower, the more pressure available to move the water.

How High Does a Water Tower Need to Be?

Typically, municipal water pressure measures somewhere between 35 to 100 psi (pounds per square inch). To provide such pressure, the height of the tower is critical. For every 2.31 feet of height, the tower exerts 1 PSI of pressure, but the design must also factor in size and terrain of the distribution area. In addition, we consider the number of homes, businesses, and industries relying on it for daily water consumption and fire protection.

In Medford, Wisconsin, where we’re currently designing a new 155-foot water tower, the terrain tends to rise and fall, which can certainly impact design. Medford’s new tower is the latest addition to a water utilities system that includes two other existing towers. Scheduled to begin operation in 2021, tower No. 3 will hold 250,000 gallons of water to serve an area of Medford that lies uphill from the rest of the system.

Due to this tower’s comparably high location, we isolated it from the current network, creating a high-pressure zone where it will be supplied with water pumped from two wells that will also be isolated in this zone. By operating independently, tower No. 3 is free to exceed the height of the existing two, and now will be built tall enough to generate sufficient pressure for the area to be served. As a result, we anticipate this high-pressure zone will be well-supplied with an average water pressure of 67 psi.

Cumberland, WI, water tower. Ayres designed a new 600,000-gallon composite water tower and 1,700 feet of water main extension for the City of Cumberland, Wisconsin, in 2011.

Ayres designed a new 600,000-gallon composite water tower and 1,700 feet of water main extension for the City of Cumberland, Wisconsin, in 2011.

What Materials Are Used in Water Pipes?

The City of Medford uses polyvinyl chloride (PVC) or high-density polyethylene (HDPE) pipes, which have gained popularity in the United States since their introduction in Germany in the 1930s. The flexible plastic pipes demonstrate excellent performance in pressure applications, including municipal water mains, where they provide a durable, corrosion resistant, and cost-effective alternative to traditional iron or steel infrastructure.

What’s the Right Water Pressure for Homes?

Residential plumbing is also subject to complications from pressure, which, if too low, can become a quite a nuisance. Residential water pressure that’s too high can damage pipes and fixtures and cause water loss, which results in unnecessary expense and needless demand on the municipal water supply. If you suspect that the water pressure in your home falls outside the normal range of 40 to 80 psi, check with your local water department or call a certified plumber to identify the problem and consider options to resolve it.

Contact any of our municipal service leads for answers to your municipal water questions.

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