Hello all, I'm not sure what this green stripe is, but the ony thing I can think of is that the copper pipe in the ground is corroding causing a green stripe on the concrete floor. Can anyone let me know what this green stripe is from, is it possible that the radiant will start leaking at any time? Just bought the house. Thanks. Edit: sorry, the pictures are larger than the file size limit allowed. But without looking at the photos, can a copper pipe inside concrete (basement floor) cause a green line above it that is 7-8 feet in length?

With 50 year old radiant yes, leaking could happen at any time, or it could go a few more decades. There isn't an easy way to tell.

A copper pipe could indeed stain the concrete. That doesn't necessarily mean it's minutes away from leaking, but it could also be an indication that it already is leaking, though the rate may be miniscule.    If it's seeping with a pin-hole leak there would probably be surface efflorescence as well as staining.

If you isolate the heating system from the potable supply with the shut off valve, does the system lose pressure?