I expect you'll get more helpful responses, but I'll ask if you have an ice maker in the refrigerator? All your plumbing and an ice maker, if any are on the passenger side.
I offer that because if a hose test can't recreate a leak, then it could be because it's not originating from outside the coach.
2008 Holiday Rambler Admiral 30PDD (Ford F-53 chassis)
2009 Honda Fit Sport