The other low point drains are for draining water out of your system for winterizing. On mine, there are two separate valves, side by side, which drain the hot and cold systems. At least one hot and one cold spigot (sink or bathroom) should be opened to let the water drain. You also have to drain the HW tank via a separate valve or plug. The FW drain is usually only one valve, but sometimes two drain hoses, which are the overflow. Hope this helps.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.