I'm in a newly purchased house built 1998. It has three outside hose bibbs, two are standard garden hose thread but one has a very fine thread that does not match either "Hose" or "Pipe" thread. I looked at Home Depot and they have all sorts of adapters for various types of threads, but nothing matching this.

Here's a picture showing the hose bibb next to a standard hose thread.

What is this thread, and what kind of adapter do I need?

enter image description here

  • 2
    Use a tape measure or a ruler next to the threads so we can get an accurate thread count. Getting an idea of what it is can help us figure out where it is needed for or what it was supposed to be used but it is hard to tell from the photo.
    – Ed Beal
    Nov 13, 2019 at 1:01
  • 1
    A photo showing the full hose bibb may help somebody recognize what it is.
    – Greg Hill
    Nov 13, 2019 at 17:04

2 Answers 2


What you see there is a vacuum breaker spigot with its pants down. You'll need to try and procure the parts or just replace the whole works.

enter image description here

More on that

  • 7
    Exactly correct. They deliberately use an incompatible thread because you are supposed to have a vacuum breaker on there... Nov 13, 2019 at 2:11
  • 3
    Spot-on isher. You’re a good go-to guy.
    – M.Mat
    Nov 13, 2019 at 5:51
  • 14
    The prior owner probably (unknowingly) unscrewed the vacuum breaker with the hose and left it on the hose. That person has probably taken the hose to their new house and is probably about to post a new question here, "why does my hose not screw on to a normal hose bib?"
    – dwizum
    Nov 13, 2019 at 14:34
  • 1
    We were missing one on our house and the only place I could find a replacement was a local small hardware store (Ace hardware in my area). They stocked the ones that most homebuilders in the area were using and the big home stores had moved on to the newer brands and styles. My point is check smaller stores or specialty plumbing supply places if you have trouble finding it.
    – JPhi1618
    Nov 13, 2019 at 15:19
  • 3
    @dwizum, the set screw you see in the second picture is designed to tighten and snap off in a lot of faucets. This is so you can't accidentally remove them. Not all designs have this, but they normally have a set screw of some kind to keep them in place.
    – JPhi1618
    Nov 13, 2019 at 15:20

it looks like a 3/4 national pipe thread(npt) ...most hardware stores have a conversion coupling to get to male hose thread (mpt)..ask for a 3/4 female iron pipe to male hose adaptor ...some of the hose bibs out there have decorative spout features that change the thread. hose bib vacumn breakers are usually the same thread fht x mht they can be added after market to a hose bib unless it came from factory pre installed they are usually permanently affixed.

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