Municipal Water

PolyPipe^® - A Leader in Total Piping System Solutions for the Municipal Water Market

PolyPipe^® offers a complete range of polyethylene (PE) piping system products. PolyPipe^® is known for quality products, superior service, state-of-the-art facilities and a team of people dedicated to the industry and our customers. PolyPipe^® is one of the largest manufacturers of pressure rated High Density Polyethylene pipe.

PolyPipe^® uses only select resins meeting our demanding standard of excellence and quality. As a result, you can safely predict the performance of any PolyPipe^® system, as specified. Whether your application calls for new construction, rehabilitation of existing lines, horizontal directional drilling, plowing or river crossing, PolyPipe^® is your total municipal water piping system solution.

Superior Flow Characteristics

Unlike other products in the market that must allow for a reduction in flow capacity over time, the smooth inner surface of PolyPipe^® HDPE pipe remains relatively constant for the life of the pipe.

In addition, the smooth inner surface of PE provides a higher maximum flow rate for a given size compared to other types of piping materials.

PolyPipe^® has excellent fluid flow properties. For liquid flow under pressure, the Hazen-Williams equation may be used with a value of 150 for "C".

Even though HDPE pipe will typically have thicker walls than ductile iron, comparable flow rates can be achieved with a smaller ID for HDPE. By utilizing PolyPipe^® high-density polyethylene (HDPE) with its smoother surface, the pipeline ID can be 3.8–15.4% smaller than ductile iron pipe.

PolyPipe^®: Meeting the demands of the water market

• Applications include Potable Water, Reclaim Water, Intake Water, Raw Water and Waste Water
• Heat-fused, fully restrained, leak proof joints
• Flexible and lightweight
• Maintains optimum flow rates
• Improved flow, reduced pumping costs
• Superior corrosion, chemical and abrasion resistance
• Durability, long-term strength and integrity
• Pipe, fittings, custom fabrications and valves provide total system solutions
• Sub-zero temperatures do not cause failure
• No damaging effects from freeze-thaw cycles
• Black HDPE contains a minimum of 2% carbon black to protect against ultraviolet degradation, which eliminates storage problems
• Flexibility allows for fewer fittings
• Wide variety of joining methods, including fittings for transition to other piping materials
• Material of choice for trenchless technology
• Excellent resistance to water hammer events – 100% for occasional surges, 50% recurring surges, (see AWWA C-901 and C-906).

Pressure ratings, Working pressure ratings and Water hammer

The inherent advantages of PolyPipe^® HDPE pipe, when compared to a rigid piping system, lie in the material's ability to withstand continuous system pressures with additional surges resulting from dynamic events such as an instantaneous change in water velocity. Fused lengths of HDPE pipe, as opposed to gasket push joints, can also eliminate thrust blocking requirements.

Design Pressure Rating (PR)

The pressure rating of PolyPipe^® polyethylene pipe is determined in accordance with the Plastics Pipe Institute (PPI) recommended hydrostatic design basis for the material and the physical dimensions of the pipe. Pressure design calculations are based on the "ISO" equation, which relates the stress on the pipe to the internal pressure.

working pressure (WP) and working pressure rating (WPR)

Per AWWA, the working pressure (WP) is defined as the maximum anticipated, sustained operating pressure applied to the pipe exclusive of transient pressures.

For recurring pressure surges, the sum of the WP and maximum anticipated recurring pressure surge may not exceed 1.5 times the pipe's nominal pressure class. For occasional pressure surges, this value may not exceed two times the pipe's nominal pressure class.

The WPR establishes a pipe's pressure design capacity for the anticipated system temperature and surge pressure conditions. The WPR, which considers pipe DR system surges and temperature, must be equal to or greater than the WP of the system with consideration for the effect of anticipated pressure surges.

WPR>WP

By comparison, AWWA defines working pressure rating for PVC to be equal to or less than the pressure rating of the pipe depending on the safety factor and allowances for pressure surge.

For further explanation, please refer to AWWA C-906, "Polyethylene Pressure Pipe and Fittings, 4" through 65", for Water Distribution and Transmission."

The following graph shows the relationship between WPR and flow rate for HDPE and PVC. It is important to note that the WPR for HDPE may not need derating for flow rates of up to 4 ft/sec. As a result, comparable DR's can typically be used for both HDPE and PVC for typical system design flow rates of 4 – 5 ft/sec.

pressure surge and water hammer events

Water hammer in a piping system is best described as a hydraulic transient pressure and is a sudden change in pressure due to fluctuations in the velocity of flowing fluids. The change in velocity can be caused due to sudden opening or closing of valves, a pump shutdown or start-up, a pump failure or other dynamic event.

The magnitude of the pressure wave and associated pressure surge can be calculated using equations provided in the AWWA design manuals or PolyPipe^® Design and Engineering Guide for Polyethylene Pipe. By using these equations, the magnitude of the expected surge pressure and the total system pressure can be compared for different piping materials.

Different materials respond to water hammer events in different ways. This depends on the material's ability to dissipate the energy from the pressure wave.

The elastic properties of polyethylene absorb a significant amount of the energy from a pressure surge in comparison to more rigid materials such as ductile iron and PVC.

This elasticity provides for a reduction of the shock wave. As a result, HDPE pipe can withstand repetitive surges up to 150% and occasional surges up to 200% of the design operating pressure. This characteristic of HDPE means that the system is not "over designed" to handle water hammer and may result in a cost savings for the piping system.

High Density Polyethylene, Extra High Molecular Weight PolyPipe^® is manufactured in accordance with one or more of the following standards: ASTM - D3035 - F714 - AWWA C-901 - AWWA C-906. In addition, this product meets NSF Standard 61 for potable water and is approved for Factory Mutual PC150 and PC200. Other dimensional standards or custom requirements are available.

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