I am installing a tankless water heater, which is an outdoor model. We are likely to use PEX when redoing the plumbing, but because the heater is outdoors, we will need to have a short, outdoor PEX run.

Are there any preferred ways to protect it from UV exposure? I've seen suggestions to paint it, I'm sure I could make a covering for it, and I don't doubt that pipe insulation would work. Is there a best-practices way though?


As noted here: Is PEX exposed to the environment OK to use? you do not want to expose the material to UV light of which there is plenty in outdoor sunlight.

If it were me I would plumb the outside connections in copper and then switch to PEX inside the building structure.

  • I had considered that, but I am interested to know if there is a solution to avoid doing so.
    – Hari Ganti
    Jan 31 '17 at 9:00
  • If there is any chance of freezing, then PEX would be better than copper. And since it can be shielded from UV, it would seem that no transition to copper would be required. What I wonder about is the threat of rodents chewing on PEX. Rodent damage to PEX would be a concern more inside the structure than outside so I would say there is little point of changing from PEX to copper for the outside pipes. Jan 31 '17 at 11:55
  • As it happens, we're going to implement this solution. There's no (real) risk of freezing in my area and rodents in the attic is not an issue either. We'll have copper outside with a brass nipple leading inside, then PEX from there.
    – Hari Ganti
    Feb 10 '17 at 18:53
  • @MichaelKaras We completed the install as you described, with copper/brass fittings on the outside. It works perfectly.
    – Hari Ganti
    Feb 21 '17 at 21:57
  • Great to hear that it worked out.
    – Michael Karas
    Feb 22 '17 at 1:25

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