One other thing - if you have an in-line water filter, maybe in the line to the kitchen sink, it should be removed and replaced with the plastic hose usually furnished with the trailer, before running anti-freeze through the lines.
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.