Boubou - not sure why you need to drain the entire unit after camping. As previously mentioned, the low point drains are there to drain the system for winterizing or for long storage. IMHO, the only reason for draining the hot water tank after camping would be to prevent unpleasant odors from occurring from some CG well water, once the tank has cooled. We have very good well water, and simply drain the HW tank when home, and refill from our well. Same with the FW tank, which get refilled with fresh well water just before the next trip.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Teddy (Jack Russell terrier)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.