THANKS FOR YOUR INPUT. I HAVE BEEN ASKED TO SORT A PROBLEM IN AN EXISTING INSTALLATION IN A 6 STOREY HOTEL. EVERY FLOOR HAS A PAIR OF 1 1/2" LPHW AND CHILLED WATER PIPES COMING FROM A RISER AT ONE END OF EACH CORRIDOR, RUNNING APPROXIMATELY 25M IN THE CIELING. 3/4" BRANCHES INTO EACH ROOM...