Have have 28bhbe. I think those drain valves are under the bathrooms sink in the floor. Opening those values drains the hot and cold water in the lines. Might just double check the integrity of those valves and make sure they are fully closed. I've never used the values, so I don't know much....
2016 Road Warrior 355
2015 Ram 3500 Cummins SRW 4x4 MegaCab ShortBed
2011 F150 ecoboost - Traded
2015 Jayflight 28 BHBE (sold)
2009 Jayflight 26 BH (sold)