There's a blue pipe (1" diameter) extending ~3 feet from the city water meter before transitioning to 1" copper, then the copper connects 2 feet later to my rusted galvanized. I've run new pex-a pipe throughout the house, copper for above-ground section (e.g. hose bibs, shut-off valve), and planned to run pvc schedule 80 to the service line. Thought the service line was copper but turns out it's a blue pipe.

How do I know if this is pex pipe or polybutylene? I don't see any markings. Appears to be connected to the copper pipe with a compression union. I don't know when it was installed. blue pipe

  • Have you asked your water utility? They may have a standard for connecting to their meters and may require you to stop your run at this rather muddy union.
    – FreeMan
    Nov 18, 2021 at 18:15
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    was hesitant to raise a flag -- I am repiping and doing other work without permits. I'll call them anyway since I know that's the most accurate way to get an answer. My plan was to remove this union and tap into the blue pipe, though I don't know why there's a 2' segment of copper between the blue and galvanized (presumably installed by the city too...)
    – Travis
    Nov 18, 2021 at 18:32
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    Probably PEX. It's not gray, which most or all PB is. If you excavate and clean about 3 feet you can likely read the printing on it. On the third hand, you don't need to know, it's got a perfectly good fitting on it already.
    – Ecnerwal
    Nov 18, 2021 at 22:36
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    thanks! I read that PB sometimes came in blue but generally was gray. Google-diving says my City recently (2017-2021) updated water meters which also points towards PEX. An hour ago the City water guy conveniently showed up and said I should be able to tap into the existing fitting with PVC, and gave me an "insert stiffener" which may come in handy for this
    – Travis
    Nov 18, 2021 at 22:43
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    PEX and PB are not your only options. it could also be MDPE
    – Jasen
    Nov 19, 2021 at 2:59

2 Answers 2


Every picture I've seen of polybutylene shows it as pale blue

polybutylene pipe

PEX is almost always bright blue (when it is blue). In addition, polybutylene breaks down over time. The chances it's survived in a water main this long is low.

  • looks correct to me. The consensus is PEX. Thanks all!
    – Travis
    Nov 19, 2021 at 0:31
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    It could be a waterworks/utility grade PE pipe for that matter Nov 19, 2021 at 2:30

The copper side of the joiner will have a standard thread, connect there. leave the mystery blue plastic side undisturbed.

Dig under the join so you can recconect it without grit getting into the threads.

  • I thought maybe it was a compression coupling, but are you saying it's probably a standard female thread? If so I can connect with a male PVC fitting
    – Travis
    Nov 19, 2021 at 6:31
  • it looks like brass, and if it it is it's a standard pipe nipple. so yeah a it should thread into other pipe fittings. for copper pipe compression fittings are just compression nuts and ferrules on a pipe nipple.
    – Jasen
    Nov 19, 2021 at 9:01

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