Viega PureFlow PEX vs. Cold Expansion

A leading competitor falsely claims that its PEX-a cold expansion fittings deliver a 25% greater flow. We performed a demonstration to show what the actual performance difference, if any, is between these two variations of PEX systems in a scenario designed to exaggerate the fitting performance.
These tests show the difference in flow performance between Viega’s PureFlow system and cold expansion systems is unnoticeable in everyday use. Additionally, it is often the fixture at the point of use that is most restrictive in residential plumbing, not the piping components behind the wall. Considering this, why choose a PEX system that has lower material ratings like the 5106 cold expansion that also causes additional wait time? Go with the Viega PureFlow system which maintains the industry’s highest ratings, allows for immediate pressurization and a 25-year warranty.
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[@JonathonNeville]

Viega, can you do this test where the line goes to a bathroom and then a kitchen and then upstairs to another bathroom and kitchen, and open multiple faucets? Quicker and cheaper than doing the full test, can you reason thru whether in that context people would notice a difference?

[@teeg3275]

I love my expansion pex it’s always a good day throwin up some pex A shit use pex A with B fittings all the time. Never use viega pex or fittings but honestly look the same in size

[@willrogersplumbing4053]

I would agree with Viega-the faucets, stops, supply lines etc are where you will notice the most difference. Trunk lines/main feeds can be sized and installed in a way to offset any differences between a cold expansion and crimp flow rates. I wish Viega was more common in my area. I use the F1807 system most and I have never had an issue in over 20 years. PEX B out performs most PEX A also in the real world. Never seen issues with PEX B, I have seen multiple issues with PEX A and PEX C. In defenses of cold expansion like F1960, the connection is solid and I have never seen or had an issue, the piping is another story issues all over the place....

[@AltPlumbingSanMarcos]

Let's do a realistic test and fill at toilet and run the shower at the same time or turn on a hose bibb or run a washing machine. This is when the pressure drops due to volume issues.

[@shawnd567]

Wow! The tub fill was very surprising! Nearly 4gpm with barely any noticable difference! I also thought the pex-a fittings would provide much better flow. Brass fittings for pex-b also have a larger diameter than the plastic ones. Hey could you run this test with 1/2 pex?

[@shawnd567]

@phillip miller Wow! I didn't think it was that high.

[@TheRealJackassJesse]

Moen Posi-temp rough in valve has a max flow of 4-6gpm at 60 psi.... These tests are to show that in typical home usage the difference in negatable. I wouldn't doubt that Uponor Wirsbo fittings do have a 25% flow difference in full flow conditions.

[@ziegle9876]

My tub fills with 15gpm....

[@JonathonNeville]

You ask if the test can be run with 1/2 PEX. I thought this test was 1/2 inch PEX. ?

[@patricklafontaine4313]

Hi, I try to know the flow of my home main water line and could not find any test on that and its hard to evaluate since I need to evaluate the velocity and it depends on flow... I can find pressure drop but I need to know the flow before to install my sprinkler system. I wish not to cut the line just to check because if it have not enough of flow I ll do differently... My main line is pex 3/4 (7/8 OD) and my static pressure is about 64 psi. Do you have an idea about the max flow? If you can tell me the flow while keeping a 40 psi pressure it would be the best since the max flow could not be use as it would drop pressure to 0. Thanks!

[@SL-uy7hc]

The true test would be to test the flow rate when using a full port hose bib or boiler drain. The tub/shower/lav all went through valves and cartridges with integrated restrictive channels which render this test useless if it's truly meant to test flow rates of pipes and fittings. This test concluded that fixtures are restrictive.

[@ScottAcy]

Exactly!

[@isabellavision]

No, this test acknowledged what is commonly known, that fixtures are restrictive, often by design, and concluded that the difference in flow rate in pex systems is negligible in real world use with those fixtures.

[@mikejones5364]

Do you drink or shower out of your hose bib? They used fixtures people use daily.

[@devanmanansingh2591]

Let's say I have a 1" full port valve and 2 GPM flows through it and I have a 1/2" valve and 2 GPM flows through it. Which valve has more flow? Answer, they both are the same, 2 GPM. How? Physics. Velocity will increase in the valve or fittings with a smaller diameter to match. Another note: a cold expansion fitting is not full sized. The I.D. of the fitting is smaller than the I.D. of the tubing and is still being inserted into the tubing. Small difference of the I.D. between Viega pureflow fittings and a cold expansion fittings. That is why the differences are minimal.

[@jeremytine]

except the real world may have multiple fixtures being fed by a single pex line/trunk being used simultaneously, at which point it may matter. Yes you could upsize the line as well, but then you will waste more hot water flushing the line.

[@alankwellsmsmba]

using a manifold with pex straight runs to each fixture resolves all issues. Just need to keep the manifold close to the water heater.

[@mikejones5364]

That's silly. Space them manifolds out for maximum flow.

[@SuperVeeZee]

This test is not designed to exaggerate fitting performance. Quite the opposite. It's designed to mask it. Household water fixtures are flow-restricted. Showerheads are commonly restricted to 1.75GPM. What this test shows is that, in all of the tested systems, the fixture was the most restrictive part, not the pipe. If you want a real show of flow rate in one piping system vs. the other, remove the fixture and shower valve. Go to a full-port valve at the end of the line. You then remove the flow-restricted fixture, and you are testing only the pipe and fittings.

[@jbarizonaa]

Tub spigot was full port or almost,

[@SuperVeeZee]

@@jbarizonaa That's true of the spout itself. But the cartridges that feed that valve likely are not. At every fixture, there is a limiting factor that is NOT the pipe and fittings. That's the point. What the test shows is that end-user experience is not really effected. That much is true. But it doesn't really refute the claim that expandable pex fittings provide more flow. It's a simple math game at the end of the day. The pipe is SDR9 CTS on both sides. If the fitting on the expansion side is the same ID of the pipe, and the fitting on the crimp side is a smaller ID than the pipe, the expansion side will have a higher maximum flow, all else being equal.

[@danielsaucedo8098]

what size pex was this test preformed with?

[@MisterRay11]

1/2”

[@RRA556]

I wonder what the difference would be if you were to run all three fixtures at the same time.

[@ziegle9876]

Because the problem is with the debit from the Clinton kitchen faucet and the Obama shower head, no the pipe. Thus this test is non-representative.

[@blitz8619]

This isnt truly an accurate test since only 1 fixture is being tested at a time. In a normal household there are couple faucets running, like a shower, washing machine, toilet. A better test was to have all 3 on.

[@jbarizonaa]

Right now Uponor has two class action suits pending, because there pex is falling apart after a few years, and it leaches chemicals in the water , don't believe me look it up yourself, I am very happy with my Viega no problems, plenty of water flow,

[@SuperVeeZee]

What's the second suit about? I'm aware of one suit regarding their color-coating process. They were basically over-cooking the pipe to apply the coating, and, over time, exposure to hot water would break it down. I had several people come in with hot-side lines that were orange with flaking coating. They've since switched to uncoated clear pipe with colored lettering.

[@JtotheRizzo]

This test is VERY MISLEADING! The difference in flow rate drastically changes when multiple fixtures are running at the same time. Example: if I am doing dishes only, flow rate is great at my kitchen sink faucet. Once my kid gets in the bath tub, it's a noticeable reduction. On top of that, once my washing machine starts running, my kitchen sink water pressure reduces down to almost a trickle. I'm sure I can speak for almost everyone by saying, "Viega, we dare you to redo this test with 3 or more fixtures running simultaneously." They'll never do it because they know the truth.

[@CJINW]

Cannot trust any data with someone that has a computer voice.

[@brl5755]

This test stinks. Plumb a fake home-style layout with larger trunk and smaller legs and retest while filling more than one fixture at a time. My family doesn't plan out or even consider simultaneous water usage while using water, neither should this test.