I have a leaky backflow preventer I'm trying to remove. It's been on for most of 10 years, and we've got pretty hard water. I've drilled out the set screw:

Image of a backflow preventer with a hole drilled out where the set screw used to be

I have some channel locks that I can use to try to remove it, but it looks like the pipe for the spigot is bent, and when I apply pressure to remove the backflow preventer with the channel locks, it seems like it's going to bend it further to the left:

Image from the top looking down on a spigot. The spigot is bent to the left, and bends more as the wrench applies pressure.

Is there something I can do to get the backflow preventer off that will not risk bending the spigot more, potentially bending or damaging the pipe supplying it?

I've sprayed a bunch of WD-40 on it, but it still doesn't budge. It seems like maybe I need to drill out more around the set screw, but I'm concerned I'll damage the spigot threads.

  • 2
    When attaching or removing threaded plumbing parts you need to use two wrenches. One to hold and one to turn. Pipe wrenches are usually better. Those fittings usually use a rubber washer for sealing, so a little damage to the threads should not prevent a good seal. The threads are more for attachment than sealing. Different fittings do use the threads for sealing.
    – crip659
    Aug 6, 2023 at 17:30
  • 1
    Make sure to replace it with a new backflow preventer (hose bibb vacuum breaker) once you get it off! Aug 6, 2023 at 19:23

1 Answer 1


When removing threaded plumbing you need to use two wrenches.

One to hold and one to turn.

Place the holding wrench as close to the wall as you can to prevent pipe bending.

If you have to, remove the valve (to protect the seal) and use some heat for aid.

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