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Community and Q&A

PEX vs Copper

cbut8995 | Posted in General Questions on

Anyone have opinions on these piping solutions and durability for an entire building build in NYC using these types of piping solutions. I have heard copper will last a lifetime but cost more upfront and PEX is good and easy to work with and a lot cheaper but will last 30-50 years. What does this mean when PEX last 30-50 years? I will have to rip open the walls and replace all piping?



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  1. JC72 | | #1

    Copper and PEX have similar lifespans.

  2. Patrick_OSullivan | | #2

    I don't believe PEX is allowed by the New York City plumbing code for potable water, but a registered design professional or licensed plumber should be able to confirm that.

    Here's a link to what seem to be the current NYC code:

    1. cbut8995 | | #4

      for NYC PEX is allowed for heating pipes for the baseboard heating but not for the hotwater in showers. One of the plumbers I have used use PEX and they always pass the rough in inspection no problem. Looking for the best piping so I have no problems ever really.

      1. Patrick_OSullivan | | #5

        > for NYC PEX is allowed for heating pipes for the baseboard heating but not for the hotwater in showers.

        So it's not allowed, but you're still considering it? Oookay.

  3. walta100 | | #3

    Copper has a large and long record for long life PEX not so much but it depends on your local environmental exposures.

    Some places the local water is corrosive enough to dissolve the copper over time and make the pipes leak.

    Some PEX can be affected by UV light and fail over time.


  4. Expert Member
    BILL WICHERS | | #6

    PEX should last similarly, or even longer than, copper pipe if you install it with compression connectors. I don't trust push-on connectors that have o-ring seals over the long term. PEX is pretty immune to corrosive stuff in the water as Walter mentioned too, which is a plus if you're in an area where that's an issue.

    I can't comment as to local NYC codes since that's not my region, but a quick call to your building department will get you an answer there. If they don't permit PEX per code, then you shouldn't be considering it for your project.


  5. Jon_R | | #7

    Apparently it's chlorine + high temperatures that are likely to cause oxidative degradation and limit PEX life to less than copper. If so, using a master mixing valve at the water heater is a good idea. Even a 10F reduction is likely to be significant. A continuous hot-water re-circulation system may be a bad idea.

    One could rather easily filter out chlorine from water before it gets to the hot water heater. While good for the PEX, it's not clear if this is helpful or harmful from a health risk standpoint.

    1. cldlhd | | #18

      That's the question I was thinking about. I have copper running to my heat pump water heater and just after so that's not an issue but around the bathroom and laundry room I was thinking about re-piping using PEX. I thought about filtering the chlorine out before the water heater but that just seems to make it much more likely that you'll have a bacteria tank along with hot water... I guess I can install a chlorine filter just downstream of the HPWH without too much difficulty. That would allow my tank to have chlorinated water and the only pipes that it would be running in would be copper. Downstream of there the hot water in the rest of the house ( kitchen sink, dishwasher, laundry room, bathroom etc) would be dechlorinated. Not sure if that would be an issue as it wouldn't be sitting stagnant very long usually, I figure as long as the hot water in the tank is chlorinated and I keep the temperature over 125°. I would be good. Any thoughts?

  6. krom | | #8

    pex is not even a little bit rodent proof.
    Mice and rats like to chew it and make holes

    1. charlie_sullivan | | #9

      My understanding of the rodent issue is that when there's a penetration through a wall, and the rodents want to get through the wall, they are inclined to see chewing the PEX as a way to get through the wall. That may indicate that it's possible to protect those spots and not have trouble otherwise, but I'm not sure there's enough information to go on to be sure of that.

    2. Expert Member
      MALCOLM TAYLOR | | #10

      If the argument against using pex is rodent problems, then why allow unshielded wiring, or PVC drains?

      1. Expert Member
        NICK KEENAN | | #12

        A lot of older cities limit or prohibit outright romex and PVC, you have to use BX and cast iron. The stated reason is that if you have a rat infestation they are a problem. It also tends to be places where unions are strong.

        1. Expert Member
          BILL WICHERS | | #14

          I had a plumber tell me that the plumbing unions liked cast iron because it took skill to install. PVC allows for DIY work to be done reliably. There is something to that.

          BX and conduit are usually required due to fire code issues. Electrical fires are less likely to start if an energized conductor faults inside of a metal shield such as EMT conduit or the spiral steel (or aluminum) armor of BX or MC cable. It's a lot harder to damage those armored cables too.

          NM is much easier to work with. MC is something of a happy medium, just make sure to use the anti shorts on the ends. Without the anti shorts (small bushings that insert into cut ends between the armor and the conductors), the sharp edge of the cut armor can slice into the insulating of the conductors. Most electricians (and myself) find ways to cut the armor to minimize this potential issue, but the anti shorts are still a good idea.


  7. Jon_R | | #11

    I wonder what is more common - an unexpected pipe freeze (perhaps heat fails while on vacation) or a rodent chew? PEX survives the former.

    1. krom | | #13

      Lots of rats in NYC tho, up here in CNY frozen pipes are an issue, but how often does it come up in the city??

  8. HyggeHus | | #15

    In 30- 50 years YOU probably wont be doing too much. I’m 37 and would be anywhere between 67 and 87 years old. That’s pretty much is a lifetime. A “lifetime” shingle from GAF is only guaranteed for 50 years. In that time some newer better product may be available that will work better for the building and the future usefulness of it. I’d stick with PEX based on the info you provided. However, I have often pondered the safety factor of plastic lines. Are they BPA free? What chemicals where used to make the plastic? Do they leach out any harmful chemicals? Not sure. Copper is the best in my opinion but a lot of plumbers will only do PEX now days. We install mostly PEX in our residential remodels.

    Good luck

    1. Expert Member
      BILL WICHERS | | #16

      >"Are they BPA free? What chemicals where used to make the plastic? Do they leach out any harmful chemicals?"

      This is stuff that comes from food container concerns. Pipes are different. The materials that usually "leach out" from plastics are plasticizers, and those materials are used to modify the structure of the plastic polymer to make it more flexible. A good example is PVC. PVC pipe is rigid, quite stiff. That's the natural state of PVC, so no plasticizers are in PVC pipe. PVC extension cords are flexible though -- that's because there are plasticizers added to the PVC material to make it flexible. Modern plasticizers are much more stable than they once were, but they're not perfect.

      PEX is an ENTIRELY different polymer. PEX is made from cross linked polyethylene, which is what PEX stands for, in a way. Polyethylene is naturally somewhat flexible, in exactly the way PEX or polyethylene spinkler pipe (the black stuff coiled up in the plumbing section of the box store) is. No plasticizers are added. The cross linking process ties the polymer chains together on the sides (simplyifing a bit here), and makes the material more durable, but doesn't add anything that will leach out, it's not that kind of process. Cross linked polyethylene has been used for decades in electrical wire insulation, including most outdoor insulated power lines like the triplex cable that serves many houses. Cross linked polyethylene is a VERY stable material -- it doesn't leach anything, and it doesn't react with hardly anything, either.

      As a side note, we use polyethylene in underground water pipes, gas pipes, and electrical conduits. It's used in the jacket of the fiber optic cables that carry all the internet data, including this post when you read it! In the utility industry, it's usually said to have a lifetime of 30 years when outdoors exposed to sunlight. I personally know of telephone cables over 50 years old that are fine, and we all think underground where there is no sunlight exposure the material will last for centuries, probably millenia. It's a really great material for many uses, it's recyclable (the "PE" mark in the triangle), it's very stable, it's nontoxic, and it's cheap. There aren't too many materials that can check all those boxes.

      I would not worry about drinking water coming through PEX lines. In some ways, it's actually safer than copper -- copper CAN release copper ions into water in certain conditions. PEX won't react to anyones drinking water.


      1. HyggeHus | | #17

        Hey Bill, thanks for the Info. I hadn't worried too much about it but have wondered, and, I will wonder no more;)

      2. andy_ | | #20

        That is a great answer. I'm bookmarking this for all the PEX skeptics that I run into.

        1. Expert Member
          MALCOLM TAYLOR | | #21


          Another argument for not getting too worked up about plumbing your house with PEX is that the water you are using has already run through plastic piping from your well, or through many miles of it from your municipal water supply.

          1. cldlhd | | #22

            No municipal water systems I know use a lot of use a lot of plastic pipe. The vast majority of I'm familiar with used ductile iron for mains.
            I'm sure part of it is regional and also based on when the system was built. I work for a municipal water system that was constructed in the early 1950s and we have no plastic water mains. I would imagine not only is it regional but maybe newer development used it for various reasons including cost. Now that I think about it though we do use it for repairs occasionally if they're too big to be clamped

          2. Expert Member
            MALCOLM TAYLOR | | #24

            Must be a regional thing. I've seen nothing but plastic in a couple of decades. I used to oversee two small community water systems. None of the suppliers I used sold anything but plastic.

          3. Expert Member
            BILL WICHERS | | #25

            Most municipal water systems are using HDPE (very similar material to PEX) for new runs of reasonable (up to maybe 1o-12 inch) size. Part of the reason for this is that the HDPE pipe can be installed by directional drilling which is a lot less disruptive to the landscape than open trenching is. Other reasons for the use of HDPE are reduced friction losses, and thermally fused joints between sections -- that means no fittings or gaskets to leak!

            Older systems used ductile iron, and a lot of the really big (6 foot) mains are/were a type of coated precast concrete I believe (I've never worked with the huge stuff myself). In my area, they occassionally even find old hollowed out logs in some areas that are very old, and that always surprises people!

            You'll find more and more new construction and replacement work is going to be done with HDPE pipe. The common HDPE water line is black with blue stripes, and it has a very thick wall. It's good stuff -- there is no reason to be afraid of it. It's not even a new material, polyethylene has been around since the early 1940's -- one of the first applications of it was in high voltage wire insulation for airborne radar systems. Polyethylene in this application offered significant weight savings compared to the rubber materials previously used.


        2. charlie_sullivan | | #23

          Unfortunately, it's not true. My previously excellent tasting tap water tasted terrible after we about 15 feet of the copper running to the kitchen sink with PEX. The plastic taste did fade with time, and was also possible to filter it out. In a previous discussion on GBA, I reported that, and other chimed in with their experiences. It seems that PEX-A imparts a taste that many can detect, and PEX-B does not, at least not nearly as much.

          Or, for a more scientific angle, here's a report on university lab measurements of what leaches out from PEX.


          1. cldlhd | | #26

            Why does there always have to be a downside? I was going to redo a area of the house with pex A as I like the connection method better than B. The plumbing there services a laundry room and a bathroom so nobody's really drinking the water from there but using it for things like brushing teeth, showers etc. Also when I read that pex A is more susceptible to hot water with chlorine makes me want to lean towards b or just stick with copper...

          2. Expert Member
            BILL WICHERS | | #27

            Flush the lines for a few hours with hot water and that should minimize any issues. It's possible there may be some residue in the pipe left over from the manufacturing process. My first thought is we might be seeing an issue similar to the drywall debacle from some years back with imported "cheap" drywall that smelled horrible.

            The polymer itself is very stable and shouldn't be a problem IF the manufacturer has made it correctly. I've heard of very unusual problems with wire manufacturers exteruding at an incorrect temperature, so I suppose this might be possible with PEX too. Quality control is important, as is not just buying whatever is cheapest at any given time.

            Plastic pipes are frequently used in labs and very complex chemical processing facilities (drug and semiconductor manufacturing plants) specifically because they are very stable, so it's not an inherent problem with the material itself.

            BTW, I've always been suspicious of fittings that seal with O rings for two reasons: 1- o rings can degrade and leak, and 2- o rings are often lubricated -- and that lubricant is in contact with the fluid flowing through the pipes. I'd be more concerned with the lubricant than with the pipe itself in terms of stuff leaching into the water.


    2. cldlhd | | #19

      I hope you live longer than 67.....I used to think that was really old but now that I'm 51 it doesn't seem as old as it used to.

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