Very slow leak out of main line at elbow out of concrete
You need to explain what the pipe is for, what fluid is inside, where is it located. From your writing you are probably looking at having to do some excavating to gain access to the pipe. If you are trying to solder a line full of something like water, It shows that you have no experience to make the necessary repairs and it time to call for professional help before you do something that can hurt you or can't easily be fixed