I want to install a medicine cabinet in my bathroom, but it won't fit in completely because the back of it bumps up against two capped copper pipes in the wall. What are they, and can I have them cut to be lower so that my cabinet will fit? Thanks! :)

Sounds like your Hot and Cold water lines.
Can be replumbed to allow the cabinet installation.
Very slight chance to do without having to repair Drywall. A good Plumber may have a good solution.

Thank you. There is a big hole in the wall where the old cabinet was, so the pipes are clearly visible. I just don't understand why they are so tall in the wall when the connection to the sink water lines are a few feet lower. Do these capped pipes allow for expansion? Or can someone explain their purpose? Thanks!

I want to install a medicine cabinet in my bathroom, but it won't fit in completely because the back of it bumps up against two capped copper pipes in the wall. What are they, and can I have them cut to be lower so that my cabinet will fit? Do these capped pipes allow for expansion?
Pretty good guess!
What you have in the wall are air chambers. We are mandated , by code, to install air chambers on each lavatory and the kitchen sink. They are there to reduce water hammer.You cam cut them back if you wish. Just replace the hard caps when you do. Good luck, Tom

OK, that's what I was thinking. Air chambers for expansion. They seem so very tall and I would only need to cut a few inches to get the cabinet in. One pipe is actually much taller than the other. How do I know when I have cut too much?

We cut our air chambers at 12" for a 1/2" pipe and 8" if we increase it to a 3/4" air chamber. They aren't necessary for your system to operate so cut them back as far as needed. Tom

Bless you!!

Good luck on your project. Cheers, Tom

They are there to prevent water hammer. When valve suddenly shuts, the water will compress the air. The air acts as a cushion so the pipes don't rattle when the lavatory/toilet suddenly shuts off.