This adapter is attached to an outdoor spigot:

Spigot with adapter

It is near the location of a former hot tub so I believe it has something to do with pressure control. When I attach a hose to it and turn it on if the hose is not flowing (e.g. a closed nozzle at the end) the water leaks (more like squirts, lots of it) from this adapter, it appears to be from the holes and not the connection to the spigot or the hose.

What is this thing? Is there a way to utilize it? I'd like to remove it so I can use this spigot but when I try to unscrew it with a wrench it does not budge - in fact the spigot itself starts to rotate. I wasn't really able to tighten a pipe wrench to the spigot due to the available clearance & pipe width.

There appears to be a rivot on the under side of the adapter but it is difficult to tell, it is somewhat rusted over.

Follow Up

My original concern was water leaking from it when it was used. While a plumber was on site doing a different job I asked him to look at this to see if something was wrong. He said the vacuum breaker wasn't working properly and ended up replacing the entire hose bib (with new vacuum breaker), I presume because he was not able to remove the vacuum breaker as well or it wasn't salvageable. Now no water spews out when it is used.

  • 1
    It looks like a anti syphon device to me, because of the petina on the faucet I'd different than the device I would guess it is aftermarket. The "rivet" may be a rusty screw to keep it from coming off.
    – Ed Beal
    Commented Jul 22, 2017 at 15:09
  • You might be able to grip the spigot body with a pipe wrench if you first remove the handle, packing nut, and stem. (If you remove only the handle, you are likely to bend or break the stem.) Commented Jul 22, 2017 at 15:15
  • Sometimes the anti-siphon device is not an add-on, yet will still have the set-screw commonly found on after-market ones. Look carefully, sometimes the portion of the device that threads onto the hose valve is actually crimped on there to prevent removal. If this is the case, you would have to replace the whole valve. Commented Jul 22, 2017 at 16:34
  • Is this a continuous flow of water for as long as the nozzle valve is closed, or is it a brief spurt and then the flow onto the ground shuts down? Commented Jul 23, 2017 at 0:06
  • You should be able to put an adjustable "crescent" wrench on the sides of the body of the spigot, without taking it apart.
    – DaveM
    Commented Jul 24, 2017 at 3:18

4 Answers 4


An anti-siphon plumbing device is a special device that has a one-way valve designed to stop the flow of potentially contaminated water back into the drinkable (potable) water supply.

Anti-siphoning capabilities are required by code on certain plumbing devices such as exterior faucets (sillcocks).

On exterior faucets or sill-cocks, the anti-siphon device protects against the risk of the faucet being connected to a hose that is immersed in contaminated water or attached to a chemical sprayer.

These special faucets keep freezing cold temperatures away from any water supply line feeding the exterior faucet. They allow remote control of the water supply faucet valve located inside the home, which then controls water flow to the exterior faucet spout. The faucet head is attached to a 6” to 20” long tube.


I agree that this appears to be an add-on device which could probably be removed with a locking pliers or pipe wrench.


I learned a little about these doo dads this year when the two on our home started leaking after the winter freeze we had in Texas. The rubber grommets inside both went bad. After trying to get them off with no success, I took a picture and headed down to my favorite plumber dude on isle 9 at our local Home Depot. He laughed and smirked a little, then told me the backstory aaannnnddd... the trick to getting it off. Apparently, the home builders - after having a few too many of these stolen from homes during & after home builds - started enforcing the installers to grind the little locking screw off so that they could not be removed without a bit of work.

That little rusted over rivet spot, that’s where this screwhead used to be.

enter image description here

I also learned that there are two options you can buy when you need to replace one of these. You can buy the commercial grade that cost on average $30 OR you can get a non-commercial grade for less than $10. According to isle 9 plumber dude, they work the same. It’s like buying a Polo; does that little embroidered horse help with function?

So I went with the non-commercial $7 one, and they’re working great. Here’s how I got them off; you’ll need a drill bit that is made for going through metal. Place the drillbit on the spot where the screw was ground off, slowly drill out the old screw. Emphasis on slowly because you don't want to screw through and into the threads on the spigot. As you drill, take breaks to stop and see if it will come off. Eventually it will.

enter image description here

  • Great first post! BTW: the name of this doodad is a hose bibb vacuum breaker FYI, and their job is to keep water from going "the wrong way" in case you accidentally have your hose sitting in a kiddie pool, puddle, or such when some dimwit busts a water main Commented Apr 10, 2021 at 15:03

This is defiantly an add on vacuum breaker. As mentioned in @isherwood's answer it is a form of anti-siphon device.

enter image description here

The device simply screws over the existing hose bib connection, adds a simple vacuum breaker, and a new hose connection on it's end. Unless it is broken, there should be no need to remove it.

Most are held in place via a set screw. This is most likely the ‘rivet’ you observed. The set screw might be might have a round head, hex head, or even a hex key. Some are designed to that you break the head of the screw off after install so that it remains permanent. Most newer codes require that hose bibs be of the anti-siphon type and this devise is often used when upgrading an existing hose bib to meet code.


This might be normal. Really!

The device you're talking about is a hose bibb vacuum breaker that protects the water system from backsiphonage. Without it, leaving your hose end in the backyard kiddie pool could turn into a real mess for you and the City if a water pipe breaks or needs to be turned off for maintenance at the wrong time.

Closing the valve on the hose nozzle creates a situation similar to backpressure, as the pressure change from the nozzle closing propagates back up the hose and pipe past the vacuum breaker. The vacuum breaker is spitting out water to keep that water from getting into your plumbing because it might not be just water -- it might have crud in it that you don't want in your plumbing.

If it spits out water all the time not just in a burst when the valve is closed though, it might be faulty or jammed inside. I'd replace it with a new one though, or if you're willing to do some plumbing, replace the whole hose bibb with a frost-free type that has an integral vacuum breaker.

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