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What the Surprising Similarities Between Drinking Straws and Plumbing Fittings Mean for System Performance

By: Jonathan Simon on August 15th, 2023

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What the Surprising Similarities Between Drinking Straws and Plumbing Fittings Mean for System Performance

Contractors  |  PEX  |  residential plumbing  |  Plumbing Systems  |  CPVC

Of all the ways to move fluid, the two that most people interact with most frequently are plumbing pipes and drinking straws. Surprisingly, there is a remarkable correlation between the diameter of common straw sizes and the internal diameter of the fittings used in PEX and FlowGuard Gold CPVC plumbing systems. By using drinking straws as a comparison, it becomes easy to see the significant differences between various plumbing fittings and why FlowGuard Gold CPVC outperforms PEX in flow and pressure.

For example, a drinking straw that you would get at a fast-food restaurant with a soda is almost exactly the same diameter as a ½” PEX crimp fitting, coming in at .32” and .315” respectively. That’s significantly less than the .38” diameter of an expansion PEX fitting, which is pretty close to the .36” diameter of a typical smoothie straw.

While expansion fittings represent an upgrade over crimp fittings in terms of internal diameter, both pale in comparison to the internal diameter of a ½” FlowGuard Gold CPVC fitting. With an internal diameter of .489”, the FlowGuard Gold CPVC fitting is slightly larger than a .48” boba or bubble tea straw, which is designed extra wide to allow the tapioca pearls in bubble tea to be consumed through the straw.

If, like me, you’ve never had bubble tea, check out the image below for a visual of the difference in diameter. Or just remember that ½” FlowGuard Gold CPVC fitting is 29% wider than a ½” PEX expansion fitting and 55% wider than a ½” PEX crimp fitting.



Some in the plumbing industry have promoted the use of 3/8” PEX; however, that makes the disparity even worse. The internal diameter of a 3/8” crimp fittings is 18% smaller than the smallest standard straw size.

The difference in the internal diameter of PEX and FlowGuard Gold CPVC fittings is a result of the design of each system—and it translates directly into performance. With FlowGuard Gold CPVC, the pipe is inserted into the fitting while PEX fittings are inserted into the pipe, narrowing the flow path at the fitting. And the narrower the diameter of the fitting, the greater the pressure loss. PEX fittings can cause up to 7-10x more pressure loss compared to a CPVC fitting.

PEX insert fittings can also create turbulent zones in the pipe as water jets out of the restriction created by the fitting, potentially exceeding the velocity limit for the pipe. These higher-velocity zones may require that the design velocity of the system be reduced to remain within manufacturer specifications.

Plumbers can try to compensate for these issues by employing home run designs for some fixtures, or upsizing PEX piping. But both of these solutions come with significantly higher material costs to overcome this inherent limitation of the PEX system.

With FlowGuard Gold CPVC you and your customers get the flow and pressure you expect without the extra cost of PEX. And that’s just one of the benefits of the FlowGuard Gold CPVC system. To learn more, download our brochure.


Download Making the Switch to FlowGuard Gold CPVC brochure now