infloor heating system leaking in concrete

It sounds alot like the Bio-Energy tube. It is black, right? The tubing, as originally conceived, is supposed to push into a punched manifold using a special tool that pushes the insert into the tubing in the manifold, pinching it in place. Yes, you can pressurize individual loops, (and from my experience you should get good at it), by building a tool with either a garden hose fitting or air fitting on one end and a hose barb on the other. The manifolds tend to pinch off the ends of the tubing spilling rusty water everywhere. The tubing tends to erode and go away...pinholes everywhere. The tubing has no oxygen barrier...ongoing corosion issues in system. They may have fixed their product since we used it in the 80's...but it cost us a ton of money, and anxiety. The systems that we managed to save now have new manifolds with push on barbs and plastic auto-motive clamps...you'll have to build your own manifolds. We isolated the tubing from anything ferrous with a heat exchanger and flushed the rust and crud out with Hercules Boiler Cleaner or TSP. Then we got aggressive with inhibitors. Most eventually had to be abandoned and new systems put in.

You can find a leak in the floor by exposing the concrete and laying clear visqueen over it...the leak will show up shortly as vapor on the underside of the visqueen and then you can dig it up and fix it in place. If the job was done right the first time, you can simply pinch off both ends of the failed tube near the manifold and go on without it. There should be enough tubing to heat the space.