During maintenance LCW may be shut off to individual branch circuits at the control racks. If it is necessary to work on the control racks LCW may be shut off at the valves located on the north side of the hall where the main LCW feed and return lines enter. When shutting down any LCW circuit branch or main you must close the supply side first (Failure to do so can trap up to 300 psi in the circuit). The return side must also be closed before service to prevent the 50 psi return pressure from back-feeding the system. Water (at 50 psi) left in the system can be drained to the nearest floor drain by attaching a hose to the purge valves located at the supply and return manifolds, on each control rack. (The bypass flow alarm on the main console could be set off by this procedure. The alarm may be reset as above by pressing the indicator button after draining is complete.)
Before pressure is reapplied purge valves must be shut. If the main supply valves at the wall were closed then the bypass and shunted test valves should be opened, as for loss of site LCW listed above. When applying pressure to the branch circuits the solenoid valves should be in the open position. Open the return valve first to bring the system up to return pressure then slowly open the manual supply valve. Always check the system for leaks after any maintenance.