PEX vs. copper

nikkirxdDecember 2, 2011

Just receiving our bids on a new home from 3 different builders. One wants to use copper the others PEX. Reading a little online, I would lean toward PEX, but professional or experienced opinions needed! Not just concerned about cost. Concerned about durability (i.e. - 50 years), fewest leaks, availability of hot water pressure when multiple faucets are running, and noise.


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PEX is durable and probably quieter than copper. It's certainly cheaper in materials and installation.

Leaks will be a result of workmanship (same with copper).
Hot water volume will be a result of proper design (same with copper).

PEX is subject to rodents chewing it. Not a problem most of the time.

    Bookmark   December 2, 2011 at 4:02PM
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Any plumbing material can be noisy if not installed properly. CPVC and copper would be most prone to noise. But PEX can be noisy. The piping must be free to move with changes in temperature. If clamped down tight, it will still move and make noise while doing so. My CPVC is offset 2' every 10' and hanging so that it touches nothing else, especially not the joists. It makes no noise.

    Bookmark   December 2, 2011 at 10:36PM
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nikkirxd both Pex and Copper have been around for a long time. Both are good. Minor differences. They become bigger differences if you have a problem with low water pressure or long distances, but an experienced plumber knows how to design your system to take care of this.

    Bookmark   December 3, 2011 at 12:22AM
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The installation of expansion turn outs such as described by Brickeye are important when designing a piping system for high pressure steam, but for the temperature range of domestic hot water it simply is not necessary...

When no flow is occuring the hot water lines will cool to the ambient temperature, which would typically be about 65 to 70degF and the code max for domestic hot water is 125degF so the resultant temperature differential is in the order of 55- 65 and the linear thermal expansion would be in the order of 1/2" to 5/8" per 100ft of pipe. If the pipe is hung with code approved pipe hangers there simply is not enough movement to cause a problem.

    Bookmark   December 3, 2011 at 4:09AM
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I prefer pex, certainly for any exterior wall applications (in northern climates). Even though it is better to try and use interior walls, that is not always possible with todays open concept floorplan. With pex you no longer have to worry about freezing pipes that crack. I also like the long direct runs without joints that might leak someday. It is nice when you have a manifold in the basement that equalizes pressure and allows for individual shutoff valves. It's also much cheaper and much faster to install...

    Bookmark   December 7, 2011 at 1:23PM
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out of curiously- what was the difference in price (%-wise) between copper and pex offers you received?

    Bookmark   December 8, 2011 at 8:36PM
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"certainly for any exterior wall applications (in northern climates). Even though it is better to try and use interior walls, that is not always possible with todays open concept floorplan. With pex you no longer have to worry about freezing pipes that crack."

WRONG- While it is true that the PEX tubing will tolerate freezing it also must be understood that when a fixture is installed in an outside wall the PEX fixture stubout is also in that outside wall, and if freezing occurs it can and generally will occur first at the fitting. If freezing occurs in the fitting it will expand the fitting wall and the PEX crimp ring so that when the line thaws and everythig returns to normal size the expanded crimp ring no longer has the correct tension and the line is likely to blow off, not to mention that the end use fitting is copper and it is subject to splitting in the same manner as copper pipe.

quote "It is nice when you have a manifold in the basement that equalizes pressure."

WRONG- a manifold does not equalize pressure. Pressure changes are a result of vertical static head & friction head in the pipe runs. If the lines are sized correctly their is no more pressure losses in a main & branch system then there are in a home run manifold system.

Quote;"allows for individual shutoff valves"

Per code, all fixtures with the exception of showers and tubs are required to have individual shutoffs and when servicing a faucett on a second floor I find it much more convenient to reach under the sink and turn the angle stop off instead of running down two flights of stairs and locating the manifold to turn the water off. (Perhaps that is why most local codes still require the angle stops even though you have a manifold system).

Quote;" It's also much cheaper"

When you factor in the cost of the manifolds & end use stub outs plus the amount of tubing required to construct a manifold system in the end the material cost will work out nearly the same if not more expensive.

Quote:" and much faster to install"

Here again, this is wrong. While it is certainly easier to fish PEX tubing than to run rigid copper to install PEX per complete code, ASTM & manufacturers specifications it reqiires MUCH MORE attention to detail, but then I doubt if one in fifty PEX installations are really up to spec.

The bottom line, if you install PEX in a standard main & branch configuration there is a substantial savings in material costs however if you install a PEX manifold system most plumbers will quote the same price as copper.

On the other hand, there is nothing that would prevent you from installing a manifold system with copper, in fact, I once worked on a Jail where they did just that. They installed a manifold in a utility closet in the hall way and a separate copper line to every shower, WC & Lav so if a prisoner should happen to tear something off the wall the guards could quickly turn that fixture off without interrupting water service to the other fixtures on the floor.

    Bookmark   December 9, 2011 at 6:23AM
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Keeping the debate alive...
PEX is subject to damage by an insect common to the NW USA and which has now spread to the east coast: the western conifer seed bug.

That's according to Uponor, manufacturer of Wirsbo, among other products.

This was Uponor's diagnosis of our leaking Wirsbo. Also note that it was Uponor that commissioned the one and only study that addresses this issue.


    Bookmark   May 15, 2014 at 12:32PM
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