Why does it matter if it's gas or water? In either case, you need to disconnect and cap it, so you need to access this pipe below the level you are working on.

Follow the pipe backwards to where it goes.

Oh, but then I'm gonna have to rip out more stuff then....

Uh yeah... the pipe is capped... so either that or gingerly remove that cap that is sealing the pipe.

It will either be a flood or a gas rush. I'm gonna bank on the fact that there is probably a really good reason that pipe is capped off.

I doubt there is any internet psychic that will tell you anything different.

It was a million to one shot doc, a million to one. I was removing a cap on a pipe and then?...... we all love stories here on Houzz so be sure to fill us in on the gory details.

You know like if it leads you to buried treasure or something. LOL.

currently I have drained water in the house so there is no water if its rads pipe but if its gas..??

down below the pipe is closed wall… its not open.

Nobody here is going to be able to look at that and tell you what that is . Call a plumber.

The pictures are very dark. Is that another pipe beside it? What material is the pipe made of? What is the diameter? I would advise calling a plumber.

Also, please tell me you aren't taking down walls without permits/ consulting an engineer.

@Yun Kim:

Nobody can reliably tell you what it is with the info provided. You will have to trace it.

AND regardless of what it is, you will have to cap it below this level. That means you either will find it in the basement and cap it - or the floor below. There is no choice to cut it off at floor level unless you are abandoning all of the existing plumbing - including the heat (cutting it in the basement, for example) and even then you better be darn sure that nothing comes out when you turn on the gas or water. Plumbing in old homes has a funny way of surprising you.

It looks a lot like the gas lines running through a house I own. Strongly suggest you hire a professional to check it out before you do anything!

Any chance these are capped off fittings for an old expansion tank for hot water heat?