Leaky riser or radiator? Best way to address leak

bipbap

So I posted before about lots of water loss and I found a spot on our ceiling where it’s mushy near a riser.

I checked the radiator directly above in the other apartment and it doesn’t appear to be leaking anywhere.

Does it seem likely to have a leak in the pipe between ceiling and floor?

The valve of the radiator above is super old so maybe that could affect things?
I don’t know if my next step should be opening the ceiling to look up or replacing the ancient valve?

I hate to open the ceiling and now give myself a bigger annoying drywall repair but I’m also hesitant to mess with an old valve when it seems to be working fine and is connected to ancient pipes that may be ready to crack.

Any thoughts on best approach?

Photos show our mushy ceiling and upstairs neighbors radiator directly above.

mattmia2

Wrap a rag around the pipe under the valve and see if it gets wet. It kind of looks like that wall above is leaking but it could just be failing plaster for other reasons.

you could pull out the piece that is about to fall anyhow and see what you see. be careful because there may be asbestos insulation on the pipe inside the ceiling that might come with it.

bipbap

Thanks for the advice, I’ll open it up a bit.

I know there isn’t any asbestos on the pipes just because we had this ceiling fully opened a few years ago when we renovated and it should be packed with Rockwool for sound between floors.