I am replacing some failed galvanized water pipe indoors. Two of the existing galvanized pipes poke straight through the exterior wall of the house, right above the foundation, and have hose bibs attached to the end. I am replacing the indoor pipe with PEX, but I'm stumped when it comes to how to get the PEX to connect to exterior plumbing. PEX, from what I've read, will degrade rapidly in the presence of UV light.

My goal is to attach a hose bib fitting to the straight across port of a tee at exterior, and connect some 3/4" LDPE poly pipe to the perpendicular port of the tee. The LDPE poly pipe will go out to a couple posts in the yard and have hose bib fittings on them.

I was planning on using PVC for the exterior plumbing, but I understand that plain white PVC cannot be used indoors for any supply plumbing, only DWV. Am I allowed some leeway to have a short (6-12") stub of PVC sticking through the exterior wall so the PEX can be connected to it?

I have a second question which is... as I have only a hole drilled through the siding of the house, how do I securely fasten the pipe coming through so that movement outside won't transfer inside?

  • Is CPVC an option for the exterior plumbing? Commented Jul 7, 2015 at 11:48

2 Answers 2


Since you mentioned freezing in some comments, I recommend this:

enter image description here

This is a freeze-proof hose bib, complete with anti-siphon valve to prevent water running backwards from your yard into your supply plumbing should the pressure go off.

  • This is sometimes called a "hydrant" valve, and you can buy a hydrant valve with a PEX fitting on the end, so you can go right from PEX to the valve, and it'll be freeze-proof. Commented Jul 10, 2016 at 14:01

Use copper pipe through the wall. It could be easily adapted with fittings for PEX on the interior and PVC for your exterior post bib runs. You can secure it to the wall with "drop-ear" fittings that have tabs with screw holes.

With the tee below, solder a 90 with a short length of copper through the wall with a threaded adapter for PEX. On the other end just solder a threaded adapter for your PVC connector. The threaded port would accept a threaded hose bib.

enter image description here

  • I agree. And for just a few connections, one may just want to go with sharkbite connectors and skip the soldering.
    – DA01
    Commented Jul 7, 2015 at 14:18
  • My concerns about using copper are twofold: I have never made sweat/soldered connections with copper, and I am concerned that it would easily burst in freezing conditions.
    – William S.
    Commented Jul 7, 2015 at 23:34
  • Then use a pre-made threaded brass nipple and utilize the same adapters and fittings as previously mentioned. PVC is just as likely to burst as copper if it freezes, you need to ensure your entire system is freeze-proof (drain exterior lines pre-freeze). Commented Jul 8, 2015 at 1:11

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