Upon arrival we found the temp/pressure relief valve on the indirect water heater was leaking. Checked the temp and pressure and found both were acceptable and not the cause of the leak. Also found a hi-vent on the indirect water heater had leaked in the past and was no longer functioning properly. After getting customer authorization we replaced the temp/pressure relief valve and the hi-vent. Attempted to fill the system back up with water and found the autofeed was plugged internally with sediment and was not allowing any water through. Removed the autofeed and installed a new autofeed, backflow preventer, and ball valve to isolate the boiler side of the autofeed. Filled system back up with water and purged all air out. Started and tested the system. Had hot water coming back on all zones. Unit is working properly