The Murrayburn contract involved a complete system drain down and cutting in of ball valves for future isolation of phased works. We then fitted a new 2 pipe heating mains throughout the school along with anchors and expansion bellows. Once complete it was a case of isolating the phase to be worked on ( 2 classrooms per phase ), drain down, strip out the existing pipework, re-pipe the existing cast radiators, connect to the new mains, test and make the phase live. There were 15 radiators to each phase and the work took about 1 week per phase from start to finish. When a phase was finished I'd then prefabricate the pipework sizes ready for the next phase.