Hello ive got a powermax 155 i called a plumber who is a friend because i had a leek on a joint he drained the system to fix the leek once done he filled the system. All the radiators are full of water the pump on the left hand side is running when i call for the central heating but no water is getting to it. The system has no filling loop or pressure gauge and the only thing that is working is the hot water. Please help