Hi. Find a point where you wish to test from, fit a valve on the pipe at this point, you need to fill the pipe work and purge air from pipes as filling via pipe caps/valves (what ever you use to cap off) once achieved. Disconnect the topping up supply and connect a proofing pump to the pipe work pump up to say 20 bar, the gauge on the pump will indicate this. If you get to this stage without problems, leave the pump for say 5 min to stabilize and then a further say 30 min, monitor the gauge for any drop in pressure. Visual inspection can also be carried out where possiable. If air is not removed prior to using the pump it will take for ever to reach pressure and is very dangerous as the air compresses can result in injury if fitting start flying about. (Water being incompressible will not have the explosive effect when the system is pressurised providing air is not present) Good Luck